Sound absorption mechanism of porous asphalt pavement
|
|
- Harry Hamilton
- 5 years ago
- Views:
Transcription
1 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) Sound absorption mechanism of porous asphalt pavement Michiyuki Yamaguchi,* Hiroshi Nakagawa,** and Takuya Mizuno*** * Bridgestone Corporation, 1, Kashio-cho, Totsuka-ku, Yokohama, Japan ** Nittobo Acoustic Engineering Co., Ltd., Midori, Sumida-ku, Tokyo, Japan *** Fukuda Road Construction Co., Ltd., 2031, Nakanoshima-ogata, Nishikawa-machi, Nishikanbara-gun, Niigata, Japan (Received 30 May 1998) The aim of this study is to clarify the sound absorption mechanism of porous asphalt pavement by comparing it with those of the glass wool and urethane foam etc., which are well-known porous sound absorbing materials. In order to elucidate the sound absorption mechanism, we measured the propagation constant and characteristic impedance of a sound wave traveling inside the material under the plane wave incident condition using an acoustic tube, and calculated the behavior of the sound waves in the material based on the measurement results. We concluded that the sound absorption of the porous asphalt pavement is caused by the following mechanism. Because the sound waves in the porous asphalt pavement material generally used in Japan exhibit less attenuation than those in glass wool or flexible urethane foam, the multi-reflected waves remain inside the material, and interfere with the wave reflected from the front surface of the material. In particular, in the frequency range below 1 khz where the sound waves exhibit less attenuation inside the material, the sound absorption coefficient peaks at a frequency at which the antiphase condition is satisfied between the multi-reflective waves in the material and the sound wave reflected from the front surface of the material. Furthermore, the frequency range above 1 khz is characterized in that since the attenuation gradually increases while the interference decreases, the sound absorption coefficient of the porous asphalt pavement is determined by its surface reflective wave. Keywords : Porous asphalt, Sound absorption mechanism, Propagation constant, Characteristic impedance, Interference of sound wave PACS number : Ev 1. INTRODUCTION Although porous asphalt pavement was developed primarily with the aim of preventing traffic accidents caused by slippery roads, its continuous porous structure was also found to have a sound absorbing effect, which makes porous asphalt pavement useful for the reduction of traffic noise. However, many aspects of the sound absorbing mechanism remain to be clarified. Although porous asphalt pavement is effective in reducing traffic noise, it is generally considered that the noise reduction does not depend only on the noise absorbing action of the road surface substructure. It appears that the decrease in tire noise due to the interaction between the tread of a tire and the road surface also contributes much to the noise reduction effect. Accordingly, it is important from the standpoint of noise reduction to clearly distinguish the role of
2 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) the substructure from the role of the interaction between the tread of a tire and the road surface. The author and others have conducted a series of studies on porous asphalt pavement material, focusing on the sound absorption property of the material. In recent years, the sound absorption property of porous asphalt pavement has been the subject of many investigations, and the Porous Asphalt Study Group, sponsored by technological development center, Nagaoka university of technology, has held two conferences and reported the results of related studies.1,2) In addition, studies by Meiarashi, et al.,3-5) a study by Hatanaka, et al.,6) a study by Iwase, et al.,7) etc. have been reported. The present report describes the sound absorption mechanism of porous asphalt pavement to clarify its role as sound absorption material, and also to search for the possibility of enhancing its sound absorptive function. 2. METHOD FOR INVESTIGATING THE SOUND ABSORPTION MECHANISM 2.1 Test Samples Porous asphalt pavement consists of a mixture of Table 1 Test samples.
3 M. YAMAGUCHI et al. : SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT crushed aggregate, sand, and limestone powder, which account for about 95 % of the whole, and modified asphalt binder which accounts for about 5% of the whole. The pavement material is reinforced by making the sand and limestone powder adhere to the surface of the crushed aggregate in order to thicken the film layer of the binder. The porous asphalt material typically used in Japan has a void ratio of about 20 %, and a thickness ranging from 40 mm to 50 mm for general roads. Samples used in this study were prepared in the laboratory using aggregate with a quite commonly used diameter ranging from 13 mm to 5 mm. Various values of void ratio and thickness were used. A number of samples (3 to 6 units) were prepared for each target void ratio and thickness, since we expected that a certain dispersion would occur during preparation. The properties of prepared samples are listed in Table 1. The apparent densities of the samples shown in, the table were obtained in the following manner. The dried samples were weighed with an accuracy of 0.1 g, and their diameter and thickness were measured with an accuracy of 0.1 mm using calipers. For each sample two mutually orthogonal 'arbitrary diameters were measured, and the thickness at two points on each diameter. The average apparent density of the samples was derived by respectively substituting the average cross-section and thickness for A and L in expression (1). Average apparent density of the samples where WS : The average weight of the samples (kg) A : The average cross-section of the samples (m2) L : The average thickness of the samples (m) In addition, the average apparent void ratio was derived from expression (2). Average apparent void ratio of the samples (1) (2) where Dm : The average apparent density of the samples (kg/m3) The theoretical maximum density* (kg/m3) * The virtual density at which the void ratio of a sample consisting of aggregate and asphalt at a certain mixing ratio becomes 0 %. (3) where Wa: The mixing ratio of asphalt (%) Da: The density of asphalt (kg/m3) The density of water at room temperature (103 kg/m3) Wi : The mixing ratio of each aggregate (%) Gi : The specific gravity of each aggregate Here, The first two digits of each test number used in the table, for example 20 of represent the target void ratio, the middle digit represents the target thickness, and the final digit represents the serial number. 2.2 Acoustic Test In order to clarify the acoustic effect of the material, use of the sound absorption coefficient alone is not sufficient to determine the internal structure of the pavement material. It is also necessary to know the state of sound wave propagation in the material. Measurement of the propagation constant and characteristic impedance enables us to determine the state of the reflection of the incident sound waves from the front surface and the attenuation of the sound waves transmitted in the material. The propagation constant and characteristic impedance are representative acoustic properties of a material. They are complex values determined on the assumption that the material is of infinite thickness. The propagation constant represents the state of attenuation and sound wave velocity when a sound wave propagates through the material, while the characteristic impedance corresponds to the ratio of sound pressure to particle velocity at any given point in the material. These characteristic values can be obtained easily in an impedance tube by using two microphones and changing the thickness of the air layer behind the sample to measure the acoustic impedance. An impedance tube method using two microphones was applied to measure the sound absorption coefficient, propagation constant, and characteristic impedance of a sound wave under the condition that a plane wave impinged perpendicularly on the front surface of the sample material. In addition, the measurement was carried out accord-
4 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) respectively. (7) (8) Fig. 1 and Block the diagram sample of the impedance where k : The atmospheric wavelength constant Z0: The atmospheric characteristic impedance As is obvious from the above, the propagation constant and characteristic impedance can be derived from expressions (5) through (8) by replacing one air layer with the other provided behind the sample. Furthermore, the sound absorption coefficient can be derived from the acoustic impedance of the surface of the sample using expression (9). tube adapter. ing to the system using a system introduced by Utsuno, et al.,8) as is shown in Fig Measurement principle The acoustic impedance Z1 at the front surface of a test sample with thickness L can be represented using the acoustic impedance Z2 at the opposite surface of the sample with expression (4). (4) where Zc: The characteristicimpedance γ: Zc The and propagation γ can be constant represented of the sample of the sample. by expressions (5) and (6). (5) (9) Measurement method As described in Paragraph above, in order to obtain the propagation constant and characteristic impedance, it is necessary to measure two types of acoustic impedance of the sample by replacing one air layer with the other. In this study, as shown in Fig. 1, we used an acoustic tube having a movable stiff wall (piston) behind the air layer and a loud speaker toward the front surface of the sample. Then, a pseudo-random sound signal emitted from the loud speaker is received by microphones 1 and 2 so that the transfer function H between the microphones 1 and 2 can be measured using a 2-channel FFT analyzer. Thus, the acoustic impedance Z1 of the sample at the front surface in the acoustic tube using air layer L0 could be derived from expression (10). (6) (10) where Z1 or Z1' : The acoustic impedance of a sample with thickness L plus air layer L0 or L0', which is sandwiched between the sample and the movable piston, as viewed from the front surface of the sample. Further, Z2 or Z2' is the acoustic impedance of a closed tube of air layer L0 or L0' sandwiched between the sample and the movable piston, as viewed from the opposite surface of the sample. They are represented by expressions (7) and (8), 32 where DX : The spacing between microphones LX : The distance between microphone front surface of the sample 1 and 2 1 and the Next, the acoustic impedance of the surface of the sample due to the preparation of air layer L0' behind the sample was obtained in a similar manner, and Zc and crushed tube, tube γ were calculated. aggregate placing may cause Since is not the sample sound well fitted directly leakage asample made of to the impedance in the impedance so that it is difficult to
5 M. YAMAGUCHI et al. : SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT obtain a correct measured value. We, therefore, prepared an adapter as shown in Fig. 1, and placed the sample in the adapter. In order to enhance the fit between the sample and the inner wall of the impedance tube, the sample was wrapped with adhesive fabric tape to eliminate any gap between the inner wall of the tube and the sample. Furthermore, the outer diameter of the sample was reduced to 100 mm. The measurements were made for two different frequency bands. The first frequency band covered the range from 80 to 400 Hz with a sound receiving interval DX of 300 mm and an FFT frequency resolution f of 0.5 Hz, and the second frequency band covered the range from 200 to 2 khz peaks prominently in the frequency range below 1 khz. The sound absorption characteristic in the frequency range above 1 khz differs from that in the frequency range below 1 khz. This result suggests that the sound absorption mechanism differs between the frequencies below and above 1 khz as long as the void ratio is greater than 14 % Relationship between sample thickness and sound absorption coefficient Figures 8, 5, and 9 show the results of measuring the sound absorption coefficient of material with a fixed void ratio (target value : 20 %) and a target material thickness of 30 mm, 60 mm and 90 mm, with a sound receiving interval Dx of 70 mm, and an FFT frequency resolution f of 4 Hz. The sound receiving interval was set in such a way that the first microphone was fixed, while the second microphone was movable. 3. MEASUREMENT RESULTS 3.1 Sound absorption coefficient Relationship between void ratio and sound absorption coefficient Figures 2 through 7 show the measurement results of the sound absorption coefficient of samples of dense asphalt and porous asphalt with a fixed target thickness of 60 mm and with a target void ratio of 14 %, 17 %, 20 %, 23 %, and 26 %, respectively. The curves in the figures indicate that the sound absorption characteristic appears at a,void ratio of 17 % and greater, while the sound absorption coefficient Fig. 3 Sound absorption characteristics of porous asphalt samples (Target void ratio : 14%). Fig. 2 Sound absorption characteristics of dense asphalt samples. Fig. 4 Sound absorption characteristics of porous asphalt samples (Target void ratio : 17%).
6 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) Fig. 5 Sound absorption characteristics of porous asphalt samples (Target void ratio : 20%). Fig. 7 Sound absorption characteristics of porous asphalt samples (Target void ratio : 26%). Fig. 6 Sound absorption characteristics of porous asphalt samples (Target void ratio : 23%). Fig. 8 Sound absorption characteristics of porous asphalt samples (Target thickness : 30 mm). respectively. These figures show that when the thickness is doubled or tripled from 30 mm to 60 mm or 90 mm, the sound absorption peak in the frequency range below 1 khz is shifted down to nearly 1/2 or 1/3 of the original frequency, respectively. This suggests that there is a certain relationship between the sound absorption and the thickness of the sample in the frequency range below 1 khz. 3.2 Acoustic Characteristics of the Material The above-mentioned sound absorption characteristics indicates that there is a difference in the sound absorption patterns of usual porous asphalt pavement material in frequencies below and above 1 khz. In order to investigate possible causes of such a difference, we measured the propagation constant and characteristic impedance of a porous asphalt pavement sample, and for each void ratio shown in Figs. 2 through 7. Figures 10 through 12 show the measurement results for the propagation constant and characteristic impedance. The real part of the propagation constant is the attenuation constant ƒ, which is the attenuation per unit length in the sound wave propagation. Figure 10 shows the attenua-
7 M. YAMAGUCHI et al.: SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT Fig. 11 Phase velocity of sound wave in porous asphalt samples. Fig. 9 Sound absorption characteristics of porous asphalt samples (Target thickness : 90 mm). Fig. 12 Characteristic impedance of porous asphalt samples. Fig. 10 Sound attenuation characteristics in porous asphalt samples. tion per centimeter in units of db. The imaginary part of the propagation constant is the phase constant Ĉ, which can be represented by expression 2 Ĕf / Cm, where Cm is the propagation velocity (phase velocity) of the sound wave in the material, and f is the frequency. Figure 11 shows the phase velocity calculated using this expression. The characteristic impedance Zc is shown with the atmospheric characteristic impedance Z0 used as the reference value Attenuation constant From Fig. 10 and Figs. 2 through 7, it can be seen that the attenuation of sound waves inside the sample is not necessarily marked in the frequency range below 1 khz where the sound absorption coefficient peaks. Although the attenuation increases as the void ratio decreases, it can be inferred that the increase in sound absorption in this frequency range is not due to the attenuation inside the sample. In the frequency range above 1 khz, the attenuation inside the sample gradually increases, and this tendency becomes conspicuous as the void ratio decreases. It can be inferred that the sound absorption in this range is due to the attenuation inside the material Phase velocity As shown in Fig. 11, the phase velocity in the sample drops to about 100 m/s, or less than 1/3 of the atmospheric phase velocity. The phase velocity decreases further as void ratio decreases Characteristic impedance As is obvious from Fig. 12, the characteristic
8 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) impedance is fairly high compared with the atmospheric characteristic impedance. Since the sample material has a stiff skeletal structure with a void ratio as low as less than 26 %, only the air inside the material is considered to be subject to the elastic deformation caused by the sound wave. Accordingly, it can be inferred that the sound particle motion is considerably obstructed by the rigid structure of the sample. 3.3 The Future Problems to Solve The data of the sound absorption coefficient shown in Fig. 2 through 9 exhibits a certain dispersion compared to nominal values. This dispersion cannot be explained by differences in the void ratio and thickness of the sample alone. Therefore, it is necessary to determine the relationship between the internal structure of the sample and the acoustic characteristics. A possible clue to the resolution of a cause of such dispersion is to compare the properties of samples used in our test with the chart prepared by Delany and Bazley9) who experimentally demonstrated, using fabric sound absorbing material, the existence of a certain relationship between the flow resistance, characteristic impedance, and propagation constant. We intend to investigate a possible cause of the dispersion in the future. 4. SOUND WAVE BEHAVIOR IN RELATION TO THE MATERIAL 4.1 Sound Reflection from a Sample with Infinite Thickness The behavior of an incident sound wave on the front surface of the sample in relation to the properties of the sample material, based on experimental values such as the propagation constant, characteristic impedance, etc. Assuming that a sound wave is incident on a sample of infinite thickness, the incident sound pressure pi, the sound pressure Pr reflected from the front surface of the sample, and the sound pressure pt transmitted into the sample can be represented by expressions (11), (12), and (13), respectively.m) The sound pressure amplitude of the incident wave is assumed to be a unit value, whet (13) The distance (depth) of a measured point from the front surface of the sample (m) The atmospheric wavelength constant (radian/m) The atmospheric and material characteristic impedances (N s/ m3) The propagation constant of the material : The attenuation constant of the material (napers/m) (1 naper/m = db/m) The atmospheric and material sound velocities (m/s) Measured values of the propagation constant and characteristic impedance were substituted into expressions (11) through (13) to determine the behaviors of the sound waves. The behaviors of the sound waves of representative samples numbered and , which previously showed the acoustic characteristics described in Section 3.2 are shown in Figs. 13 through 16, the behaviors of the sound wave in the frequency range below 1 khz in which the sound absorption coefficient peaks are shown in Figs. 13 and 15, and the behaviors of the sound waves at a frequency of 1.5 khz are shown in Figs. 14 and 16. Similar results were obtained for the other samples. The following conclusions may be drawn: (1) At the frequency within the frequency range (11) (12) Fig. 13 Sound propagation at most absorbing frequency (568 Hz) of the sample
9 M. YAMAGUCHI et al.: SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT Fig. 14 Sound propagation at 1.5 khz of the sample Fig. 15 Sound propagation at most absorbing frequency (392 Hz) of the sample Fig. 16 Sound propagation at 1.5 khz of the sample below 1 khz at which the sound absorption coefficient peaks, nearly the same quantity of the reflected wave as that of the incident sound wave occur on the front surface of the sample. This reflected wave is somewhat reduced at a frequency of 1.5 khz, and the reflected wave with a greater void ratio generates less reflected wave. (2) At the frequency within the frequency range below 1 khz at which the sound absorption coefficient peaks, the sound wave transmitted through the sample exhibits little attenuation over a distance as small as the thickness of the sample. This tendency is prominent for samples with higher void ratio. (3) At a frequency of 1.5 khz, all the waves transmitted through inside the samples attenuate rapidly. 4.2 Multiple Sound Reflection from a Sample with Finite Thickness As shown in Figs. 13 and 15, at the frequency below 1 khz at which the sound absorption coefficient peaks, the sound waves are propagated in the sample without attenuation. However, since the sample has a finite thickness, the waves arriving at the opposite surface of the sample reflected from that surface, change their directions and return to the front surface of the sample. Moreover, since the opposite surface of the sample is in contact with a stiff wall, which is actually the base layer for the porous asphalt pavement, complete reflection occurs on the opposite surface. Since the samples are nearly 6 cm thick, the pressure of the sound waves that were reflected from the opposite surface of the samples and returned to the front surface corresponds to the sound pressure of the transmitted waves that traveled a distance of 12 cm. As the figures show, because the phase of the reflected waves is opposite to that of the incident wave, the sound waves that are reflected from the opposite surface, returned to the front surface, and are then emitted from the front surface into the air cause destructive antiphase interference with the wave reflected directly from the front surface. Therefore, we attempted to ascertain the effects of such interference through further calculation. When a transmitted wave represented by expression (13) is transmitted to the sample with thickness L, is totally reflected from a stiff wall, and is then returned to the front surface of the sample, the sound pressure by pt0 and particle velocity vt0 of the transmitted wave can be represented by expressions (14) and (15), respectively.
10 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) (14) (15) When this transmitted wave is reflected from the stiff wall and returned to the front surface of the sample, the returned wave is partly reflected from the front surface of the sample back into the sample and the rest is transmitted into the atmosphere. If the sound pressure and particle velocity of the former wave reflected back into the sample and those of the latter wave transmitted into the atmosphere are denoted by pt1, vt1, Pr1, and vr1, they are represented by expressions (16) through (19), respectively, where Pt1 and Pr1 are the sound pressure amplitudes of the reflected and transmitted waves. (16) (17) (18) (19) At x = 0, since the sound pressures and particle velocities of the reflected and transmitted waves must be equal on both sides of the boundary surface, the amplitudes of the sound pressures and those of the particle velocities are represented by expressions (20) and (21), using the preceding expressions (14) through (19). (20) (21) Therefore, the sound pressure amplitude of the reflected wave and that of the transmitted wave on the front surface of the sample are represented by expressions (22) and (23), respectively. (22) (23) Accordingly, when this reflection is repeated N Fig. 17 Sound propagation at most absorbing frequency (880 Hz) of the sample times in the sample sandwiched between the air and the stiff wall, the amplitude of the sound wave ptn that again returns from the front surface to the sample material and that of the sound wave prn that is emitted to the air can be represented by expressions (24) and (25), respectively. (24) (25) Expressions (24) and (25) were used to plot the behaviors of the sound waves at the frequency below 1 khz at which the sound absorption coefficient peaks for the thinnest sample, numbered (void ratio 21.4 %, and thickness 30 mm). The behaviors of the sound waves reflected a number of times (N =1 to 5) in the sample at the abovementioned frequency (880 Hz) are plotted in Fig. 17. The multi-reflected waves ((4)) are partly emitted into the air in the phase opposite to the incident wave ((5)), and destructively interfere with the wave ((2)) directly reflected from the the sample, resulting in the decrease in the total sound pressure at the front surface of the sample ((6)), or resulting in the increase in the sound absorption coefficient. 4.3 Calculation of the Sound Absorption Coefficient The apparent sound absorption coefficient of the porous asphalt sample was derived, based on the above concept, from expression (26) using the sound pressure amplitude obtained on the front surface
11 M. YAMAGUCHI et al.: SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT (x=0) of the sample. (26) The sound absorption coefficient was calculated for three test samples , and under three conditions of sound reflection ; (1) only the direct reflection from the front surface of the sample was considered (i.e. PrN=0), (2) one reflection and (3) five reflections from the opposite surface of the sample material was considered. The results of calculation are shown in Figs. 18 through 20, together with those obtained from expression (9), which are expressed as 'measured' in the figures. sample is taken into consideration, the calculated value approaches the value of the sound absorption coefficient obtained from expression (9). In contrast, if the effects of the waves reflected from the opposite surface on the sound absorption coefficient at frequencies other than the peak frequency are taken into account, the sound absorption coefficient decreases further. It is clear that the reflective wave from the front surface of the sample and those from the opposite surface interfere with each other in this frequency range. On the other hand, in the frequencies higher than the frequency at which the Since the porous asphalt samples have high impedance, the amplitude of the waves reflected from the front surface is large. The sound absorption coefficient calculated from these reflected waves is nearly constant at around % until the frequency reaches a certain value, and then it increases. This phenomenon indicates that the amplitude of the transmitted waves increased in the higher frequency range. Next, by considering the aforementioned prominent peak of the sound absorption coefficient in the frequency range below 1 khz, it is clarified that although the sound absorption coefficient ranges only from about 20 to 30 % if the waves reflected from the opposite surface are not considered as described above, but if these reflected waves are taken into consideration, the aforementioned peak of the sound absorption coefficient appear. Furthermore, if the multi-reflection in the Fig. 19 Comparison of measured absorption coefficient with calculated absorption coefficient of the sample Fig. 18 Comparison of measured absorption coefficient with calculated absorption coefficient of the sample Fig. 20 Comparison of measured absorption coefficient with calculated absorption coefficient of the sample
12 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) sound absorption coefficients of these samples peak and further higher than the frequency at which the sound absorption coefficients of these samples dip, the interference is not so high as that in those lower frequencies although the interference still remains, and the attenuation inside the samples is considerable. In summary, the sound absorption property of the porous asphalt pavement material is divided into two frequency ranges. In the former frequency range, the sound absorption coefficient of the porous asphalt material is determined by the interference between the sound wave reflected from the front surface of the material and that from the opposite surface of the material. In the latter frequency range, the sound absorption coefficient of the material is determined by the attenuation of the sound wave inside the material, proving that the porous asphalt pavement material has such a absorption mechanism as mentioned above. 5. COMPARISON WITH OTHER POROUS MATERIALS Porous asphalt material was compared with various other porous sound absorbing materials including glass wool, flexible urethane foam and another type of porous sound absorbing material made of thin sheets of cloth (apparent density : 220 kg/m3, thickness : 1.6 mm) with an air space (9.5 cm thick) between them (See Fig. 21). In addition, the cloth of the sample consisting of cloth/air-layer/cloth shown in Fig. 21 was prepared integrally so as to entirely cover both the front and back surfaces of the sample. The acoustic characteristics of these porous sound absorbing materials were measured in the same manner as those of the porous asphalt samples. The difference in the sound absorption characteristics between the porous asphalt pavement material and the conventional porous materials is described in the following sections. 5.1 Glass Wool and Flexible Urethane Foam The acoustic characteristics of glass wool samples GW-1 and GW-2, which have apparent densities of 38 kg/m3 and 97 kg/m3 and thicknesses of 50.6 mm and 25.7 mm, are shown in Fig. 22 (measured propagation constant), and Fig. 23 (measured characteristic impedance). The acoustic characteristics of flexible urethane foam samples U-1 and U-2, which have apparent densities of 36 kg/m3 and 35 kg/m3 and thicknesses of 19.4 mm and 19.8 mm are shown Fig. 22 Sound propagation characteristics in the glass wool samples. Fig. 21 Arrangement of the thin cloth/airlayer/thin cloth sample. Fig. 23 Characteristic impedance of the glass wool samples.
13 M. YAMAGUCHI et al.: SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT Fig. 24 Sound propagation characteristics in the flexible urethane foam samples. Fig. 26 Comparison of measured absorption coefficient with calculated absorption coefficient of the glass wool samples. Fig. 25 Characteristic impedance of the flexible urethane foam samples. in Fig. 24 (measured propagation constant), and Fig. 25 (measured characteristic impedance). Comparison of the results for our porous asphalt drain sample with those for the glass wool samples and flexible urethane foam samples shows that the internal sound attenuation characteristic of our porous asphalt sample is similar to those of the latter samples when the void ratio is less than 17 %. From these acoustic characteristics of the glass wool and flexible urethane foam samples, their sound absorption coefficients were calculated for N= 1 and N= 1 to 2 using expressions (24) through (26) in the same manner as for our porous asphalt sample. The results for the glass wool samples are shown in Fig. 26, and those for the flexible urethane foam samples in Figs. 27 and 28, respectively. Each of Fig. 27 Comparison of measured absorption coefficient with calculated absorption coefficient of the flexible urethane foam sample (U-1). these figures includes the case in which the waves reflected from the opposite surface of the sample are not considered, i.e., the result of calculation in the case of PrN=0 using expression (26). Since the glass wool and flexible urethane foam have low
14 J. Acoust. Soc. Jpn. (E) 20, 1 (1999) impedance, there is less reflection from the front surfaces of these materials. Also, due to the high degree of attenuation inside the material, these samples exhibit weaker interference than the porous asphalt samples. In the glass wool, the sound absorption characteristic is clearly observed over the entire frequency range. In this respect, the flexible urethane foam shows weaker interference than that of the porous asphalt sample, but a certain degree of destructive interference appears just above 1 khz. 5.2 Cloth/Air-Layer/Cloth This material is known to exhibit a peak in the sound absorption coefficient at the frequency at which the thickness of the air layer corresponds to one-quarter of the wavelength of the sound wave (a sample with such a thickness is hereinafter referred to as a 1/4-wavelength sample). Such a sample was tested for comparison because it shows a peak similar to that of the porous asphalt sample. Figure 29 shows the propagation constant of the sample Fig. 30 Characteristic impedance of the thin cloth/air-layer/thin cloth sample. Fig. 28 Comparison of measured absorption coefficient with calculated absorption coefficient of the flexible urethane foam sample (U-2). Fig. 29 Sound propagation characteristics in the thin cloth/air-layer/thin cloth sample. Fig. 31 Comparison of measured absorption coefficient with calculated absorption coefficient of the thin cloth/air-layer/thin cloth sample.
15 M. YAMAGUCHI et al.: SOUND ABSORPTION MECHANISM OF POROUS ASPHALT PAVEMENT material, Fig. 30 the measured result of the characteristic impedance of the material, and Fig. 31 the result of calculation and measurement arranged in a manner similar to those in Section 5.1. Since there is almost no reflection from the front surface of the sample over the entire frequency range, the sound absorption characteristic is determined by the reflective wave from the opposite surface of the sample. The sound absorption mechanism is clearly different from that of the porous asphalt sample. 6. CONCLUSIONS This investigation has clarified the sound absorption mechanism of porous asphalt pavement material. Our conclusions are summarized as follows.. (1) Although the thickness of glass wool or flexible urethane foam for use in a typical architectural space is in the range from 20 to 50 mm, while the usual thickness of porous asphalt pavement is in the range from 40 to 50 mm, since the sound absorption property of these types of material contains the interference which mutually acts between the wave reflected from the front surface of the material and the waves reflected from the opposite surface, the wave inside the porous asphalt material is less attenuated than that in glass wool or flexible urethane foam, and the multi-reflective waves remain inside the porous asphalt material and interfere with the wave reflected from the front surface. In the frequency band below 1 khz, where the internal wave attenuation is particularly,small, the sound absorption coefficient peaks at a frequency at which the antiphase condition is satisfied between the reflected multi-reflective waves and the wave reflected from the front surface of the material. Moreover, since the attenuation gradually increases and the interference decreases in the frequency band above 1 khz, the sound absorption coefficient of the porous asphalt material is determined by the wave reflected from the front surface of the material. (2) As described in Paragraph (1) above, the frequency at which the sound absorption coefficient peaks is determined by the thickness of the material and its internal void structure, and when the thickness is doubled or tripled, the frequency at which the sound absorption coefficient peaks is shifted down to 1/2 or 1/3. (3) The sound absorption peak of the porous asphalt sample mentioned in Paragraph (1) is caused by a completely different mechanism from that in a 1/4-wavelength sample. (4) The sound absorption coefficient of porous asphalt pavement material can be predicted using expressions (12), (25), and (26) taking into consideration the multi-reflection inside the material, the propagation constant, and the characteristic impedance. Since these mathematical expressions yield accurate results for glass wool and others, it appears that they are also applicable to other porous materials. (5) The characteristics of the sound adsorption coefficient of the present porous asphalt pavement material are primarily determined by the structure of the material. It is, therefore, a problem to be solved in the future to enhance the internal sound wave attenuation as long as the material is used for sound absorption. REFERENCES 1) The First Proceedings, Issued from the Porous Asphalt Study Group, Sponsored by Technological Development Center, Nagaoka University of Technology (1992) (in Japanese). 2) The Second Proceedings, Issued from the Porous Asphalt Study Group, Sponsored by Technological Development Center, Nagaoka University of Technology (1996) (in Japanese). 3) S. Meiarashi, T. Miyagawa, and M. Ishida, "Absorption characteristics of drainage asphalt pavement," J. Acoust. Soc. Jpn. (J) 49, (1993) (in Japanese). 4) S. Meiarashi, M. Ishida, and T. Kaku, "Consideration on noise reduction factors of drainage asphalt pavement and its appreciation," J. Acoust. Soc. Jpn. (J) 49, (1993) (in Japanese). 5) S. Meiarashi and T. Fujiwara, "Sound absorption characteristics of porous elastic road surface," Tech. Rep. Noise Vib. Acoust. Soc. Jpn. N (1995) (in Japanese). 6) H. Hatanaka, K. Yamamoto, and Y. Terakado, "An acoustic characteristics of the drainage asphalt," Tech. Rep. Noise Vib. Acoust. Soc. Jpn. N (1997) (in Japanese). 7) T. Iwase and R. Kawabata, "Some acoustic characteristics of porous asphalt," Tech. Rep. Noise Vib. Acoust. Soc. Jpn. N (1997) (in Japanese). 8) H. Utsuno, T. Tanaka, and T. Fujikawa, "Transfer function method for measuring characteristic impedance and propagation constant of porous materials," J. Acoust. Soc. Am. 86, (1989). 9) M. E. Delany and E. N. Bazley, "Acoustical properties of fibrous absorbent materials," Appl. Acoust. 3, (1970). 10) Y. Kohashi, Sound and Sound Wave (Shokabou, Tokyo,1969), p. 94 (in Japanese). 43
Improvements to the Two-Thickness Method for Deriving Acoustic Properties of Materials
Baltimore, Maryland NOISE-CON 4 4 July 2 4 Improvements to the Two-Thickness Method for Deriving Acoustic Properties of Materials Daniel L. Palumbo Michael G. Jones Jacob Klos NASA Langley Research Center
More informationUltrasonic Guided Wave Testing of Cylindrical Bars
18th World Conference on Nondestructive Testing, 16-2 April 212, Durban, South Africa Ultrasonic Guided Wave Testing of Cylindrical Bars Masanari Shoji, Takashi Sawada NTT Energy and Environment Systems
More informationModule 2 WAVE PROPAGATION (Lectures 7 to 9)
Module 2 WAVE PROPAGATION (Lectures 7 to 9) Lecture 9 Topics 2.4 WAVES IN A LAYERED BODY 2.4.1 One-dimensional case: material boundary in an infinite rod 2.4.2 Three dimensional case: inclined waves 2.5
More informationModeling Diffraction of an Edge Between Surfaces with Different Materials
Modeling Diffraction of an Edge Between Surfaces with Different Materials Tapio Lokki, Ville Pulkki Helsinki University of Technology Telecommunications Software and Multimedia Laboratory P.O.Box 5400,
More informationActive Control of Sound Transmission through an Aperture in a Thin Wall
Fort Lauderdale, Florida NOISE-CON 04 04 September 8-0 Active Control of Sound Transmission through an Aperture in a Thin Wall Ingrid Magnusson Teresa Pamies Jordi Romeu Acoustics and Mechanical Engineering
More informationIn situ assessment of the normal incidence sound absorption coefficient of asphalt mixtures with a new impedance tube
Invited Paper In situ assessment of the normal incidence sound absorption coefficient of asphalt mixtures with a new impedance tube Freitas E. 1, Raimundo I. 1, Inácio O. 2, Pereira P. 1 1 Universidade
More informationIsolation Scanner. Advanced evaluation of wellbore integrity
Isolation Scanner Advanced evaluation of wellbore integrity Isolation Scanner* cement evaluation service integrates the conventional pulse-echo technique with flexural wave propagation to fully characterize
More informationESTIMATED ECHO PULSE FROM OBSTACLE CALCULATED BY FDTD FOR AERO ULTRASONIC SENSOR
ESTIMATED ECHO PULSE FROM OBSTACLE CALCULATED BY FDTD FOR AERO ULTRASONIC SENSOR PACS REFERENCE: 43.28.Js Endoh Nobuyuki; Tanaka Yukihisa; Tsuchiya Takenobu Kanagawa University 27-1, Rokkakubashi, Kanagawa-ku
More informationValidation of the Experimental Setup for the Determination of Transmission Loss of Known Reactive Muffler Model by Using Finite Element Method
Validation of the Experimental Setup for the etermination of Transmission Loss of Known Reactive Muffler Model by Using Finite Element Method M.B. Jadhav, A. P. Bhattu Abstract: The expansion chamber is
More informationMethod of Determining Effect of Heat on Mortar by Using Aerial Ultrasonic Waves with Finite Amplitude
Proceedings of 20 th International Congress on Acoustics, ICA 2010 23-27 August 2010, Sydney, Australia Method of Determining Effect of Heat on Mortar by Using Aerial Ultrasonic Waves with Finite Amplitude
More informationMulti-spectral acoustical imaging
Multi-spectral acoustical imaging Kentaro NAKAMURA 1 ; Xinhua GUO 2 1 Tokyo Institute of Technology, Japan 2 University of Technology, China ABSTRACT Visualization of object through acoustic waves is generally
More informationInvestigation of An Acoustic Temperature Transducer and its Application for Heater Temperature Measurement
American Journal of Applied Sciences 4 (5): 294-299, 7 ISSN 1546-9239 7 Science Publications Corresponding Author: Investigation of An Acoustic Temperature Transducer and its Application for Heater Temperature
More informationFrom concert halls to noise barriers : attenuation from interference gratings
From concert halls to noise barriers : attenuation from interference gratings Davies, WJ Title Authors Type URL Published Date 22 From concert halls to noise barriers : attenuation from interference gratings
More informationResonance Tube Lab 9
HB 03-30-01 Resonance Tube Lab 9 1 Resonance Tube Lab 9 Equipment SWS, complete resonance tube (tube, piston assembly, speaker stand, piston stand, mike with adaptors, channel), voltage sensor, 1.5 m leads
More informationSound absorption of Helmholtz resonator included a winding built-in neck extension
Sound absorption of Helmholtz resonator included a winding built-in neck extension Shinsuke NAKANISHI 1 1 Hiroshima International University, Japan ABSTRACT Acoustic resonant absorber like a perforated
More informationFACADE OF PERFORATED PLATE: ANALYSIS OF ITS ACOUSTIC BEHAVIOR
SCIENTIFIC RESEARCH AND EDUCATION IN THE AIR FORCE-AFASES 2016 FACADE OF PERFORATED PLATE: ANALYSIS OF ITS ACOUSTIC BEHAVIOR Alina-Elena CREȚU Military Technical Academy, Bucharest, Romania DOI: 10.19062/2247-3173.2016.18.1.43
More informationinter.noise 2000 The 29th International Congress and Exhibition on Noise Control Engineering August 2000, Nice, FRANCE
Copyright SFA - InterNoise 2000 1 inter.noise 2000 The 29th International Congress and Exhibition on Noise Control Engineering 27-30 August 2000, Nice, FRANCE I-INCE Classification: 2.5 SOUND-BASED METHOD
More information19 th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007 ACOUSTICAL ASPECTS OF THE SAGRADA FAMILIA CHURCH
19 th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007 ACOUSTICAL ASPECTS OF THE SAGRADA FAMILIA CHURCH PACS: 43.55.Gx Yoshikawa, Shigeru; Narita, Takafumi 1 ; Nishimoto, Yasuko 2 Dept. of
More informationEWGAE 2010 Vienna, 8th to 10th September
EWGAE 2010 Vienna, 8th to 10th September Frequencies and Amplitudes of AE Signals in a Plate as a Function of Source Rise Time M. A. HAMSTAD University of Denver, Department of Mechanical and Materials
More informationRayleigh Wave Interaction and Mode Conversion in a Delamination
Rayleigh Wave Interaction and Mode Conversion in a Delamination Sunil Kishore Chakrapani a, Vinay Dayal, a and Jamie Dunt b a Department of Aerospace Engineering & Center for NDE, Iowa State University,
More informationResonance Tube. 1 Purpose. 2 Theory. 2.1 Air As A Spring. 2.2 Traveling Sound Waves in Air
Resonance Tube Equipment Capstone, complete resonance tube (tube, piston assembly, speaker stand, piston stand, mike with adaptors, channel), voltage sensor, 1.5 m leads (2), (room) thermometer, flat rubber
More informationSupplementary User Manual for BSWA Impedance Tube Measurement Systems
Supplementary User Manual for BSWA Impedance Tube Measurement Systems 1 P age Contents Software Installation... 3 Absorption Measurements -- ASTM Method... 4 Hardware Set-Up... 4 Sound card Settings...
More informationSound absorption and reflection with coupled tubes
Sound absorption and reflection with coupled tubes Abstract Frits van der Eerden University of Twente, Department of Mechanical Engineering (WB-TMK) P.O. Box 27, 75 AE Enschede, The Netherlands f.j.m.vandereerden@wb.utwente.nl
More informationPanPhonics Panels in Active Control of Sound
PanPhonics White Paper PanPhonics Panels in Active Control of Sound Seppo Uosukainen VTT Building and Transport Contents Introduction... 1 Active control of sound... 1 Interference... 2 Control system...
More informationA Novel Crack Location Method Based on the Reflection Coefficients of Guided Waves
18th World Conference on Non-destructive Testing, 16-20 April 2012, Durban, South Africa A Novel Crack Location Method Based on the Reflection Coefficients of Guided Waves Qiang FAN, Zhenyu HUANG, Dayue
More informationEffect of Bulk Density on the Acoustic Performance of Thermally Bonded Nonwovens
Effect of Bulk Density on the Acoustic Performance of Thermally Bonded Nonwovens Wenbin Zhu 1, Vidya Nandikolla 2, Brian George 1 1 Philadelphia University, Philadelphia, PA UNITED STATES 2 California
More informationEnhancing the low frequency vibration reduction performance of plates with embedded Acoustic Black Holes
Enhancing the low frequency vibration reduction performance of plates with embedded Acoustic Black Holes Stephen C. CONLON 1 ; John B. FAHNLINE 1 ; Fabio SEMPERLOTTI ; Philip A. FEURTADO 1 1 Applied Research
More informationAcoustic Doppler Effect
Acoustic Doppler Effect TEP Related Topics Wave propagation, Doppler shift of frequency Principle If an emitter of sound or a detector is set into motion relative to the medium of propagation, the frequency
More informationImplementation of decentralized active control of power transformer noise
Implementation of decentralized active control of power transformer noise P. Micheau, E. Leboucher, A. Berry G.A.U.S., Université de Sherbrooke, 25 boulevard de l Université,J1K 2R1, Québec, Canada Philippe.micheau@gme.usherb.ca
More informationA Road Traffic Noise Evaluation System Considering A Stereoscopic Sound Field UsingVirtual Reality Technology
APCOM & ISCM -4 th December, 03, Singapore A Road Traffic Noise Evaluation System Considering A Stereoscopic Sound Field UsingVirtual Reality Technology *Kou Ejima¹, Kazuo Kashiyama, Masaki Tanigawa and
More informationDetection of Protective Coating Disbonds in Pipe Using Circumferential Guided Waves
17th World Conference on Nondestructive Testing, 25-28 Oct 2008, Shanghai, China Detection of Protective Coating Disbonds in Pipe Using Circumferential Guided Waves Jason K. Van Velsor Pennsylvania State
More informationProceedings of Meetings on Acoustics
Proceedings of Meetings on Acoustics Volume 19, 2013 http://acousticalsociety.org/ ICA 2013 Montreal Montreal, Canada 2-7 June 2013 Signal Processing in Acoustics Session 1pSPa: Nearfield Acoustical Holography
More informationMeasurement of acoustic reflection characteristics of
J. Acoust. Soc. Jpn. (E) 11, 4 (1990) Measurement of acoustic reflection characteristics of the human cheek Naohisa Kamiyama, Nobuhiro Miki, and Nobuo Nagai Research Institute of Applied Electricity, Hokkaido
More informationProceedings of Meetings on Acoustics
Proceedings of Meetings on Acoustics Volume 19, 2013 http://acousticalsociety.org/ ICA 2013 Montreal Montreal, Canada 2-7 June 2013 Physical Acoustics Session 4aPA: Nonlinear Acoustics I 4aPA8. Radiation
More informationCountermeasure for Reducing Micro-pressure Wave Emitted from Railway Tunnel by Installing Hood at the Exit of Tunnel
PAPER Countermeasure for Reducing Micro-pressure Wave Emitted from Railway Tunnel by Installing Hood at the Exit of Tunnel Sanetoshi SAITO Senior Researcher, Laboratory Head, Tokuzo MIYACHI, Dr. Eng. Assistant
More informationattempt to understand if we can identify a relationship between fundamental mode propagation and the condition of the cement bonds.
Hua Wang*, Mike Fehler,Earth Resources Lab,Massachusetts Institute of Technology,Cambridge, MA, USA Summary We use a 3D Finite Difference (3DFD) method to simulate monopole wavefields in a singly-cased
More informationUltrasonic Air-Coupled Non-Destructive Testing of Aerospace Components
ECNDT 2006 - We.1.1.5 Ultrasonic Air-Coupled Non-Destructive Testing of Aerospace Components Rymantas KAZYS, Andrius DEMCENKO, Liudas MAZEIKA, Reimondas SLITERIS, Egidijus ZUKAUSKAS, Ultrasound Institute
More informationUltrasonic Level Detection Technology. ultra-wave
Ultrasonic Level Detection Technology ultra-wave 1 Definitions Sound - The propagation of pressure waves through air or other media Medium - A material through which sound can travel Vacuum - The absence
More informationTime Reversal FEM Modelling in Thin Aluminium Plates for Defects Detection
ECNDT - Poster 39 Time Reversal FEM Modelling in Thin Aluminium Plates for Defects Detection Yago GÓMEZ-ULLATE, Instituto de Acústica CSIC, Madrid, Spain Francisco MONTERO DE ESPINOSA, Instituto de Acústica
More informationResonance Tube. 1 Purpose. 2 Theory. 2.1 Air As A Spring. 2.2 Traveling Sound Waves in Air
Resonance Tube Equipment Capstone, complete resonance tube (tube, piston assembly, speaker stand, piston stand, mike with adapters, channel), voltage sensor, 1.5 m leads (2), (room) thermometer, flat rubber
More informationProfessor Emeritus, University of Tokyo, Tokyo, Japan Phone: ;
17th World Conference on Nondestructive Testing, 25-28 Oct 2008, Shanghai, China New Ultrasonic Guided Wave Testing using Remote Excitation of Trapped Energy Mode Morio ONOE 1, Kenji OKA 2 and Takanobu
More informationAcoustic Filter Copyright Ultrasonic Noise Acoustic Filters
OVERVIEW Ultrasonic Noise Acoustic Filters JAMES E. GALLAGHER, P.E. Savant Measurement Corporation Kingwood, TX USA The increasing use of Multi-path ultrasonic meters for natural gas applications has lead
More informationAttenuation of low frequency underwater noise using arrays of air-filled resonators
Attenuation of low frequency underwater noise using arrays of air-filled resonators Mark S. WOCHNER 1 Kevin M. LEE 2 ; Andrew R. MCNEESE 2 ; Preston S. WILSON 3 1 AdBm Corp, 3925 W. Braker Ln, 3 rd Floor,
More informationVisualization of internal damage in RC slab with single side access attenuation tomography
PROGRESS in ACOUSTIC EMISSION XVIII, JSNDI & IIIAE More info about this article: http://www.ndt.net/?id=21562 Visualization of internal damage in RC slab with single side access attenuation tomography
More informationNONLINEAR C-SCAN ACOUSTIC MICROSCOPE AND ITS APPLICATION TO CHARACTERIZATION OF DIFFUSION- BONDED INTERFACES OF DIFFERENT METALS
NONLINEAR C-SCAN ACOUSTIC MICROSCOPE AND ITS APPLICATION TO CHARACTERIZATION OF DIFFUSION- BONDED INTERFACES OF DIFFERENT METALS K. Kawashima 1, M. Murase 1, Y. Ohara 1, R. Yamada 2, H. Horio 2, T. Miya
More informationTyre Cavity Coupling Resonance and Countermeasures Zamri Mohamed 1,a, Laith Egab 2,b and Xu Wang 2,c
Tyre Cavity Coupling Resonance and Countermeasures Zamri Mohamed 1,a, Laith Egab,b and Xu Wang,c 1 Fakulti Kej. Mekanikal, Univ. Malaysia Pahang, Malaysia 1, School of Aerospace, Mechanical and Manufacturing
More informationMEASURING SOUND INSULATION OF BUILDING FAÇADES: INTERFERENCE EFFECTS, AND REPRODUCIBILITY
MEASURING SOUND INSULATION OF BUILDING FAÇADES: INTERFERENCE EFFECTS, AND REPRODUCIBILITY U. Berardi, E. Cirillo, F. Martellotta Dipartimento di Architettura ed Urbanistica - Politecnico di Bari, via Orabona
More informationMode Dispersion Curves
Mode Dispersion Curves Fluid-Filled Pipe using FEM George Grigoropoulos Civil Engineer, MSc. g.grigoropoulos@gmail.com Department of Civil and Environmental Engineering Hong Kong University of Science
More informationEQUIVALENT THROAT TECHNOLOGY
EQUIVALENT THROAT TECHNOLOGY Modern audio frequency reproduction systems use transducers to convert electrical energy to acoustical energy. Systems used for the reinforcement of speech and music are referred
More informationPenetration of VLF Radio Waves through the Ionosphere
Penetration of VLF Radio Waves through the Ionosphere By Ken-ichi MAEDA and Hiroshi OYA Kyoto University, Kyoto, Japan (Read May 24; Received November 25, 1962) Abstract The rate of energy penetration
More informationFEKO-Based Method for Electromagnetic Simulation of Carcass Wires Embedded in Vehicle Tires
ACES JOURNAL, VOL. 26, NO. 3, MARCH 2011 217 FEKO-Based Method for Electromagnetic Simulation of Carcass Wires Embedded in Vehicle Tires Nguyen Quoc Dinh 1, Takashi Teranishi 1, Naobumi Michishita 1, Yoshihide
More informationPhased Array Velocity Sensor Operational Advantages and Data Analysis
Phased Array Velocity Sensor Operational Advantages and Data Analysis Matt Burdyny, Omer Poroy and Dr. Peter Spain Abstract - In recent years the underwater navigation industry has expanded into more diverse
More informationHydrate plug localization and characterization using guided waves
11th European Conference on Non-Destructive Testing (ECNDT 2014), October 6-10, 2014, Prague, Czech Republic Hydrate plug localization and characterization using guided waves More Info at Open Access Database
More informationHEALTH MONITORING OF ROCK BOLTS USING ULTRASONIC GUIDED WAVES
HEALTH MONITORING OF ROCK BOLTS USING ULTRASONIC GUIDED WAVES C. He 1, J. K. Van Velsor 2, C. M. Lee 2, and J. L. Rose 2 1 Beijing University of Technology, Beijing, 100022 2 The Pennsylvania State University,
More informationOblique incidence measurement setup for millimeter wave EM absorbers
Oblique incidence measurement setup for millimeter wave EM absorbers Shinichiro Yamamoto a) and Kenichi Hatakeyama Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji-shi, Hyogo 671
More informationULTRASONIC DEFECT DETECTION IN BILLET USING TIME- OF-FLIGHT OF BOTTOM ECHO
ULTRASONIC DEFECT DETECTION IN BILLET USING TIME- OF-FLIGHT OF BOTTOM ECHO Ryusuke Miyamoto Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Ibaraki 305-8573 Japan
More informationA Desktop Procedure for Measuring the Transmission Loss of Automotive Door Seals
Purdue University Purdue e-pubs Publications of the Ray W. Herrick Laboratories School of Mechanical Engineering 6-14-2017 A Desktop Procedure for Measuring the Transmission Loss of Automotive Door Seals
More informationSection 1: Sound. Sound and Light Section 1
Sound and Light Section 1 Section 1: Sound Preview Key Ideas Bellringer Properties of Sound Sound Intensity and Decibel Level Musical Instruments Hearing and the Ear The Ear Ultrasound and Sonar Sound
More informationAcoustic-Laser Vibrometry for Standoff Detection of Defects in Materials
11th European Conference on Non-Destructive Testing (ECNDT 214), October 6-1, 214, Prague, Czech Republic Acoustic-Laser Vibrometry for Standoff Detection of Defects in Materials Oral BUYUKOZTURK 1, Justin
More informationSOUND. Second, the energy is transferred from the source in the form of a longitudinal sound wave.
SOUND - we can distinguish three aspects of any sound. First, there must be a source for a sound. As with any wave, the source of a sound wave is a vibrating object. Second, the energy is transferred from
More informationMULTIPLE-LEAF SOUND ABSORBERS WITH MICROPERFORATED PANELS: AN OVERVIEW
MULTIPLE-LEAF SOUND ABSORBERS WITH MICROPERFORATED PANELS: AN OVERVIEW Kimihiro Sakagami 1,** ; Motoki Yairi 2 ; Masayuki Morimoto 1 1 Environmental Acoustics Lab., Graduate School of Engineering, Kobe
More informationThe spatial structure of an acoustic wave propagating through a layer with high sound speed gradient
The spatial structure of an acoustic wave propagating through a layer with high sound speed gradient Alex ZINOVIEV 1 ; David W. BARTEL 2 1,2 Defence Science and Technology Organisation, Australia ABSTRACT
More informationTheoretical Aircraft Overflight Sound Peak Shape
Theoretical Aircraft Overflight Sound Peak Shape Introduction and Overview This report summarizes work to characterize an analytical model of aircraft overflight noise peak shapes which matches well with
More informationElectronic Noise Effects on Fundamental Lamb-Mode Acoustic Emission Signal Arrival Times Determined Using Wavelet Transform Results
DGZfP-Proceedings BB 9-CD Lecture 62 EWGAE 24 Electronic Noise Effects on Fundamental Lamb-Mode Acoustic Emission Signal Arrival Times Determined Using Wavelet Transform Results Marvin A. Hamstad University
More informationMODELLING AND EXPERIMENTS FOR THE DEVELOPMENT OF A GUIDED WAVE LIQUID LEVEL SENSOR
Proceedings of the National Seminar & Exhibition on Non-Destructive Evaluation NDE 2011, December 8-10, 2011 MODELLING AND EXPERIMENTS FOR THE DEVELOPMENT OF A GUIDED WAVE LIQUID LEVEL SENSOR Subhash N.N
More informationULTRASONIC GUIDED WAVE ANNULAR ARRAY TRANSDUCERS FOR STRUCTURAL HEALTH MONITORING
ULTRASONIC GUIDED WAVE ANNULAR ARRAY TRANSDUCERS FOR STRUCTURAL HEALTH MONITORING H. Gao, M. J. Guers, J.L. Rose, G. (Xiaoliang) Zhao 2, and C. Kwan 2 Department of Engineering Science and Mechanics, The
More informationFinite element simulation of photoacoustic fiber optic sensors for surface rust detection on a steel rod
Finite element simulation of photoacoustic fiber optic sensors for surface rust detection on a steel rod Qixiang Tang a, Jones Owusu Twumasi a, Jie Hu a, Xingwei Wang b and Tzuyang Yu a a Department of
More informationName: Lab Partner: Section:
Chapter 11 Wave Phenomena Name: Lab Partner: Section: 11.1 Purpose Wave phenomena using sound waves will be explored in this experiment. Standing waves and beats will be examined. The speed of sound will
More informationResonant Tubes A N A N
1 Resonant Tubes Introduction: Resonance is a phenomenon which is peculiar to oscillating systems. One example of resonance is the famous crystal champagne glass and opera singer. If you tap a champagne
More informationEFFECTS OF LATERAL PLATE DIMENSIONS ON ACOUSTIC EMISSION SIGNALS FROM DIPOLE SOURCES. M. A. HAMSTAD*, A. O'GALLAGHER and J. GARY
EFFECTS OF LATERAL PLATE DIMENSIONS ON ACOUSTIC EMISSION SIGNALS FROM DIPOLE SOURCES ABSTRACT M. A. HAMSTAD*, A. O'GALLAGHER and J. GARY National Institute of Standards and Technology, Boulder, CO 835
More informationComputational optimisation of the acoustic performance of mufflers for sleep apnoea devices
Paper Number 65, Proceedings of ACOUSTICS 211 2-4 November 211, Gold Coast, Australia Computational optimisation of the acoustic performance of mufflers for sleep apnoea devices Peter Jones and Nicole
More informationImpact of etch factor on characteristic impedance, crosstalk and board density
IMAPS 2012 - San Diego, California, USA, 45th International Symposium on Microelectronics Impact of etch factor on characteristic impedance, crosstalk and board density Abdelghani Renbi, Arash Risseh,
More informationIn situ impulse response method of oblique incidence sound absorption coefficient with microphone array
doi:10.21311/002.31.5.08 In situ impulse response method of oblique incidence sound absorption coefficient with microphone array Jin Hua 1, Tianhu Wang 2 1 Engineering Training Center, Nanjing Forestry
More informationENHANCEMENT OF THE TRANSMISSION LOSS OF DOUBLE PANELS BY MEANS OF ACTIVELY CONTROLLING THE CAVITY SOUND FIELD
ENHANCEMENT OF THE TRANSMISSION LOSS OF DOUBLE PANELS BY MEANS OF ACTIVELY CONTROLLING THE CAVITY SOUND FIELD André Jakob, Michael Möser Technische Universität Berlin, Institut für Technische Akustik,
More informationCHAPTER 12 SOUND. Sound: Sound is a form of energy which produces a sensation of hearing in our ears.
CHAPTER 12 SOUND Sound: Sound is a form of energy which produces a sensation of hearing in our ears. Production of Sound Sound is produced due to the vibration of objects. Vibration is the rapid to and
More informationNew Instrument for Rock Bolt Inspection Using Guided Waves
11th European Conference on Non-Destructive Testing (ECNDT 2014), October 6-10, 2014, Prague, Czech Republic New Instrument for Rock Bolt Inspection Using Guided Waves More Info at Open Access Database
More informationPRODUCT DATA. Applications. Uses
PRODUCT DATA Impedance Tube Kit (50 Hz 6.4 khz) Type 4206 Impedance Tube Kit (100 Hz 3.2 khz) Type 4206-A Transmission Loss Tube Kit (50 Hz 6.4 khz) Type 4206-T Brüel & Kjær offers a complete range of
More informationNONDESTRUCTIVE EVALUATION OF CLOSED CRACKS USING AN ULTRASONIC TRANSIT TIMING METHOD J. Takatsubo 1, H. Tsuda 1, B. Wang 1
NONDESTRUCTIVE EVALUATION OF CLOSED CRACKS USING AN ULTRASONIC TRANSIT TIMING METHOD J. Takatsubo 1, H. Tsuda 1, B. Wang 1 1 National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
More informationLow frequency sound reproduction in irregular rooms using CABS (Control Acoustic Bass System) Celestinos, Adrian; Nielsen, Sofus Birkedal
Aalborg Universitet Low frequency sound reproduction in irregular rooms using CABS (Control Acoustic Bass System) Celestinos, Adrian; Nielsen, Sofus Birkedal Published in: Acustica United with Acta Acustica
More informationKeywords: Ultrasonic Testing (UT), Air-coupled, Contact-free, Bond, Weld, Composites
Single-Sided Contact-Free Ultrasonic Testing A New Air-Coupled Inspection Technology for Weld and Bond Testing M. Kiel, R. Steinhausen, A. Bodi 1, and M. Lucas 1 Research Center for Ultrasonics - Forschungszentrum
More informationLow wavenumber reflectors
Low wavenumber reflectors Low wavenumber reflectors John C. Bancroft ABSTRACT A numerical modelling environment was created to accurately evaluate reflections from a D interface that has a smooth transition
More informationWAVES. Chapter Fifteen MCQ I
Chapter Fifteen WAVES MCQ I 15.1 Water waves produced by a motor boat sailing in water are (a) neither longitudinal nor transverse. (b) both longitudinal and transverse. (c) only longitudinal. (d) only
More informationEnvironmental Noise Propagation
Environmental Noise Propagation How loud is a 1-ton truck? That depends very much on how far away you are, and whether you are in front of a barrier or behind it. Many other factors affect the noise level,
More informationAnalysis on Acoustic Attenuation by Periodic Array Structure EH KWEE DOE 1, WIN PA PA MYO 2
www.semargroup.org, www.ijsetr.com ISSN 2319-8885 Vol.03,Issue.24 September-2014, Pages:4885-4889 Analysis on Acoustic Attenuation by Periodic Array Structure EH KWEE DOE 1, WIN PA PA MYO 2 1 Dept of Mechanical
More informationApplication of Ultrasonic Guided Waves for Characterization of Defects in Pipeline of Nuclear Power Plants. Younho Cho
Application of Ultrasonic Guided Waves for Characterization of Defects in Pipeline of Nuclear Power Plants Younho Cho School of Mechanical Engineering, Pusan National University, Korea ABSTRACT State-of-art
More informationChapter 12: Transmission Lines. EET-223: RF Communication Circuits Walter Lara
Chapter 12: Transmission Lines EET-223: RF Communication Circuits Walter Lara Introduction A transmission line can be defined as the conductive connections between system elements that carry signal power.
More informationPerforated Flexible Membrane Insertion Influence on The Sound Absorption Performance of Cavity Backed Micro Perforated Panel
7th International Conference on Physics and Its Applications 2014 (ICOPIA 2014) Perforated Flexible Membrane Insertion Influence on The Sound Absorption Performance of Cavity Backed Micro Perforated Panel
More informationMeasuring the Speed of Sound in Air Using a Smartphone and a Cardboard Tube
Measuring the Speed of Sound in Air Using a Smartphone and a Cardboard Tube arxiv:1812.06732v1 [physics.ed-ph] 17 Dec 2018 Abstract Simen Hellesund University of Oslo This paper demonstrates a variation
More informationChapter 14, Sound. 1. When a sine wave is used to represent a sound wave, the crest corresponds to:
CHAPTER 14 1. When a sine wave is used to represent a sound wave, the crest corresponds to: a. rarefaction b. condensation c. point where molecules vibrate at a right angle to the direction of wave travel
More informationSimple Feedback Structure of Active Noise Control in a Duct
Strojniški vestnik - Journal of Mechanical Engineering 54(28)1, 649-654 Paper received: 6.9.27 UDC 534.83 Paper accepted: 7.7.28 Simple Feedback Structure of Active Noise Control in a Duct Jan Černetič
More informationCHAPTER 7 DEVELOPMENT OF CHEMICAL BONDED NONWOVEN FABRICS MADE FROM RECLAIMED FIBERS FOR SOUND ABSORPTION BEHAVIOUR
99 CHAPTER 7 DEVELOPMENT OF CHEMICAL BONDED NONWOVEN FABRICS MADE FROM RECLAIMED FIBERS FOR SOUND ABSORPTION BEHAVIOUR 7.1 INTRODUCTION Nonwoven is a kind of fabric with orientation or random arrangement
More informationChapter Ray and Wave Optics
109 Chapter Ray and Wave Optics 1. An astronomical telescope has a large aperture to [2002] reduce spherical aberration have high resolution increase span of observation have low dispersion. 2. If two
More information(A) 2f (B) 2 f (C) f ( D) 2 (E) 2
1. A small vibrating object S moves across the surface of a ripple tank producing the wave fronts shown above. The wave fronts move with speed v. The object is traveling in what direction and with what
More informationDetermination of the Structural Integrity of a Wind Turbine Blade Using Ultrasonic Pulse Echo Reflectometry
International Journal of Engineering and Technology Volume 3 No. 5, May, 2013 Determination of the Structural Integrity of a Wind Turbine Blade Using Ultrasonic Pulse Echo Reflectometry Benjamin Ayibapreye
More informationInvestigating Electromagnetic and Acoustic Properties of Loudspeakers Using Phase Sensitive Equipment
Investigating Electromagnetic and Acoustic Properties of Loudspeakers Using Phase Sensitive Equipment Katherine Butler Department of Physics, DePaul University ABSTRACT The goal of this project was to
More informationUse of parabolic reflector to amplify in-air signals generated during impact-echo testing
Use of parabolic reflector to amplify in-air signals generated during impact-echo testing Xiaowei Dai, Jinying Zhu, a) and Yi-Te Tsai Department of Civil, Architectural and Environmental Engineering, The
More informationApplication Note. Airbag Noise Measurements
Airbag Noise Measurements Headquarters Skovlytoften 33 2840 Holte Denmark Tel: +45 45 66 40 46 E-mail: gras@gras.dk Web: gras.dk Airbag Noise Measurements* Per Rasmussen When an airbag inflates rapidly
More informationAppeal decision. Appeal No France. Tokyo, Japan. Tokyo, Japan
Appeal decision Appeal No. 2015-1247 France Appellant Tokyo, Japan Patent Attorney Tokyo, Japan Patent Attorney ALCATEL-LUCENT LTD. OKABE, Yuzuru YOSHIZAWA, Hiroshi The case of appeal against an examiner's
More informationUltrasonic Transmission Characteristics of Continuous Casting Slab for Medium Carbon Steel
Key Engineering Materials Online: 25-11-15 ISSN: 1662-9795, Vols. 297-3, pp 221-226 doi:1.428/www.scientific.net/kem.297-3.221 25 Trans Tech Publications, Switzerland Ultrasonic Transmission Characteristics
More informationACCURACY IMPROVEMENT ON NON-INVASIVE ULTRASONIC-DOPPLER FLOW MEASUREMENT BY UTILZING SHEAR WAVES IN METAL PIPE
4th International Symposium on Ultrasonic Doppler Method for Fluid Mechanics and Fluid Engineering Sapporo, 6.-8. September, 24 ACCURACY IMPROVEMENT ON NON-INVASIVE ULTRASONIC-DOPPLER FLOW MEASUREMENT
More information