Proceedings of Meetings on Acoustics

Transcription

1 Matui et al. Proeeding of Meeting on Aouti Volume 19, ICA 013 Montreal Montreal, Canada - 7 June 013 Signal Proeing in Aouti Seion 1pSP: Miellaneou Topi in Signal Proeing in Aouti (Poter Seion) 1pSP7. A deign of audio pot baed on eparating emiion of the arrier and ideband wave Tadahi Matui*, Daiuke Ikefuji, Maato Nakayama and Takanobu Nihiura *Correponding author' addre: Ritumeikan Univerity, Kuatu, , Shiga, Japan, i0039fx@ed.ritumei.a.jp Parametri loudpeaker, whih utilize an ultraoni of non-linear interation, i developed to ahieve audio pot. The parametri loudpeaker ha harper diretivity, but refletion and interept by emitted ound beome evere problem. Thi i beaue refletion and interept lead to an invaion of privay, and beome noie to other litener exept a target litener. Priniple of the parametri loudpeaker an formulate a non-linear interation of arrier and ideband wave in emitted ultraoni ound on air. Thi ugget that we an deign audio pot by individually emitting the arrier and ideband wave. In the preent paper, therefore, we propoe the deign method of audio pot with the eparating emiion of the arrier and ideband wave. More peifially, the audible ound i demodulated at an area where the arrier and ideband wave individually emitted from eah parametri loudpeaker are overlapped. We arried out evaluation experiment to meaure ound preure level (SPL) of demodulated audible ound. In addition, we evaluated the peeh artiulation of the demodulated audible ound with the propoed method. A a reult of evaluation experiment, we onfirmed the effetivene of the propoed method. Publihed by the Aoutial Soiety of Ameria through the Amerian Intitute of Phyi 013 Aoutial Soiety of Ameria [DOI: / ] Reeived Jan 013; publihed Jun 013 Proeeding of Meeting on Aouti, Vol. 19, (013) Page 1

2 Matui et al. INTRODUCTION A parametri loudpeaker with harper diretivity an reprodue an audible ound in the partiular area alled audio pot [1~4]. The parametri loudpeaker emit an amplitude modulated (AM) wave whih i generated by modulating amplitude of the ultraound with the audible ound. The emitted AM wave i demodulated into the original audible ound by non-linear interation in the air [4, 5]. The AM wave onit of the arrier and ideband wave. The demodulated audible ound i repreented by the differene tone between the arrier and ideband wave. In the parametri loudpeaker, refletion and intereption of emitted ound beome evere problem. Thee are beaue refletion and intereption lead to an invaion of privay. Moreover, refletion and interept beome noie to non-litener. Thu in thi paper, we propoe the deign method of the audio pot for reduing refletion and intereption. Speifially, we attempt to deign audio pot with eparating emiion the arrier and ideband wave by uing multiple parametri loudpeaker. Then, the audio pot i formed in the area inluding arrier and ideband wave. However, the harmoni ditortion our from the differene tone of the different frequeny omponent inluded in the ideband wave. It i the problem that the harmoni ditortion beome the noie. Thu, we alo try to redue the harmoni ditortion uing the ideband wave with the band-diviion. THE PRINCIPLE OF THE CONVENTIONAL PARAMETRIC LOUDSPEAKER The parametri loudpeaker emit the AM wave deigned by amplitude modulating the arrier wave with an original audible ound. AM wave onit of the arrier and ideband wave. The audible ound i reprodued a the differene tone between the arrier and ideband wave. The arrier wave v and the original audible ound v are indiated a follow: v = A in πf t, (1) v = A oπf t, () where t i time index, A and A are maximum amplitude of the arrier wave and audible ound, repetively. f and f are frequenie of the arrier wave and audible ound, repetively. From Eq. (1) and (), the AM wave v db i indiated a follow: v db = ( v + A )in πf t, = ( A o πf t + A )in πf t, A A = A in π ft + in π ( f + f ) t + in π ( f f ) t, (3) A where, A in πf t i a omponent of the arrier wave, in π ( f + f ) t i a omponent of the upper A ideband (USB), in π ( f f ) t i alo a omponent of the lower ideband (LSB). The AM method uing LSB and USB i alled double ideband (DSB) modulation method, a hown in Eq. (3). The parametri loudpeaker an reprodue the louder audible ound by the DSB modulation method. However, the harmoni ditortion our by the differene tone between the LSB and the USB [6]. The ingle ideband (SSB) modulation method ha been propoed to redue the harmoni ditortion. SSB modulation method deign the AM wave whih ha the arrier wave and ingle ideband wave (LSB or USB). SSB modulation method obtain the ingle ideband by eliminating LSB or USB from v db. In thi paper, we remove the USB from v db uing the low pa filter and generate the AM wave whih i deigned by the SSB modulation method v b. v b i indiated a follow: Proeeding of Meeting on Aouti, Vol. 19, (013) Page

3 Matui et al. A vb = A in π ft + oπ ( f f) t. (4) Smaller harmoni ditortion our by the emitted AM wave whih i deigned by SSB modulation method than that by DSB modulation method. However, the harmoni ditortion our by the differene tone of the different frequeny omponent inluded in the ideband wave. In thi paper, we define the emitting AM wave whih i deigned by the SSB modulation method a the onventional method. In the onventional method, the original audible ound i demodulated in the area of inluding emitted AM wave. The parametri loudpeaker emit the AM wave with harper diretivity. Conequently, audio pot i deigned a linear hape. However, the initial refletion of the reprodued audible ound have higher ound preure. Therefore, the initial refletion beome a noie to nonlitener who hear refletion. THE PRINCIPLE OF SEPARATING EMISSION OF THE CARRIER AND SIDEBAND WAVES The demodulated audible ound i repreented by the differene tone between the arrier and ideband wave. In thi paper, therefore, we propoe the deign method of the audio pot with eparating emiion of the arrier and ideband wave. Figure 1 how the overview of the propoed method. In Fig. 1(a), PL i the parametri loudpeaker for the arrier wave p. PL i the parametri loudpeaker for the ideband wave p. p and p are indiated a follow: p = A in πf t, (5) A p = in π ( f f) t. (6) In Fig. 1(a), in the area inluding both arrier and ideband wave, the oberved ound p 1( t a ) i indiated a follow: pa 1( t) = p( t τ ) + p( t τ ), (7) v b, (8) where, τ and τ are the time delay of the arrier and ideband wave, repetively. In the area inluding arrier and ideband wave, the frequeny omponent of the oberved audible ound p 1( t a ) are imilar to the frequeny omponent of the AM wave. Therefore, the audio pot i formed in the area inluding both arrier and ideband wave. In thi paper, the area inluding both arrier and ideband wave i alled audio pot. On the other hand, it i impoible that audible ound i demodulated in the area inluding arrier wave p without ideband wave p. However, the harmoni ditortion may our by the differene tone between two frequeny omponent inluded in the ideband wave in the area inluding ideband wave p without arrier wave p. Then, the harmoni ditortion a noie will our with the propoed method. Thu, we hould intend to redue the harmoni ditortion uing the ideband wave with the band-diviion. The harmoni ditortion are redued with the band-diviion beaue the frequeny omponent inluded in the lower or higher frequeny divided ideband wave are le than non-divided ideband wave. In Fig. 1(b), PL i the parametri loudpeaker for the arrier wave p, PL l i the parametri loudpeaker for the lower frequeny divided ideband wave p l, and PL h i alo the parametri loudpeaker for the higher frequeny divided ideband wave p h. p l and p h are indiated a follow: Al pl = in π ( f fl ) t, (9) Ah ph = in π ( f fh) t, (10) Proeeding of Meeting on Aouti, Vol. 19, (013) Page 3

4 Matui et al. (a) The propoed method with non-divided ideband wave (b) The propoed method with divided ideband wave FIGURE 1. Overview of the propoed method p = p p. (11) l + p l and p h are generated by the band-diviion for the audible ound v with the border frequeny f t, repetively. In Fig. 1(b), the oberved ound p a ( ) in the audio pot i indiated a follow: p t h = p ( t τ ) + p ( t τ ) + p ( t τ ), (1) a l h v b, (13) where, τ l and τ h are the time delay of the lower and higher frequenie whih divided ideband wave, repetively. Under the ondition that the time lag between the time delay τ l and τ h i longer, it hould be neeary that adjuting the time lag. EVALUATION EXPERIMENT Objetive Evaluation for Meauring Sound Preure Level Ditribution We arried out the objetive evaluation experiment to onfirm the effetivene of the propoed method. We meaured the ound preure level (SPL) of the audible ound with the propoed method, and with onventional method uing a parametri loudpeaker with SSB moderation method. In the audio pot, the SPL of the audible ound i higher. Thu, we expet that SPL i higher in the area inluding both arrier and ideband wave with propoed method. Table 1 how the experimental equipment and Table how the experimental ondition. Figure how the experimental environment. In Fig., PL i the parametri loudpeaker for the arrier wave, PL i the parametri loudpeaker for the ideband wave. We meaured the SPL ditribution for onfirming our expetation. Under the ondition that PL i et on 0 deg., PL i put on PL. Figure 3 how the SPL ditribution with the onventional method. From Fig. 3, we onfirmed that the audible ound wa reprodued in the linear area with the onventional method. Figure 4(a) ~ (d) how the ditribution of SPL under the ondition that PL i et on 0, 30, 90 and 150 deg., repetively. From Fig. 4(a) ~ (), we onfirmed that SPL with the propoed method i imilar to SPL with the onventional method in the audio pot. In addition, SPL out of the audio pot with the propoed method i lower. To take an example, in Fig. 3, with onventional method, the SPL i 47 db in the point of 0 m depth and 0 m width, and that i 38 db in the point of -0.3 m depth and 0 m width. On the other hand, in Fig. 4(b), with propoed method, the SPL i 46 db in the point of 0 m depth and 0 m width, and that i 5 db in the point of -0.3 m depth and 0 m width. Thu, the SPL with propoed method i imilar to the SPL with onventional method in the point of depth 0 m and width 0 m a the audio pot. In addition, the SPL with propoed method i lower 13 db than the SPL with onventional method in the point of depth -0.3 m and width 0 m. Thee how that the audio pot formed in the area inluding the both arrier and ideband wave with propoed method. Therefore, we onfirmed the effetivene of the propoed method. In Fig. 4(d), however, the SPL of the audible ound i lower than 30 db in all area. Thi i beaue that the diretion differene between the arrier and ideband wave i larger. Thu, the non-linear interation of ultraoni arely influene the wave in the area inluding both arrier and ideband wave. Proeeding of Meeting on Aouti, Vol. 19, (013) Page 4

5 Matui et al. FIGURE. Experimental environment in the objetive evaluation for meauring the SPL ditribution TABLE 1. Experimental equipment Parametri loudpeaker MITSUBISHI, MSP-50E Loudpeaker amplifier VICTOR, PS-A00 Mirophone SONY, ECM-88B A/D, D/A onverter ROLAND, UA-1010 TABLE. Experimental ondition in the objetive evaluation for meauring ound preure level ditribution Sampling frequeny 19 khz Quantization 16 bit Carrier frequeny 40 khz Ambient noie level (LA) 37 db Sound oure Japanee iolated word FIGURE 3. Experimental reult of the SPL ditribution for the onventional method Proeeding of Meeting on Aouti, Vol. 19, (013) Page 5

6 Matui et al. (a) PL = 0 deg. (b) PL = 30 deg. () PL = 90 deg. (d) PL = 150 deg. FIGURE 4. Experimental reult of the SPL ditribution for the propoed method Subjetive Evaluation for Evaluating the Speeh Artiulation We arried out the ubjetive evaluation experiment to onfirm the effetivene of the propoed method. We evaluated the peeh artiulation of the demodulated audible both ound in the audio pot and out of the audio pot with the propoed and with onventional method. In the onventional method, a parametri loudpeaker emit AM wave with SSB moderation method. The experimental equipment are the ame a the objetive evaluation. Figure 5 how the experimental environment. Table 3 how the experimental ondition. In Fig. 5, Mi.1 i et in the audio pot and Mi. i alo et out of the audio pot. The experiment i onduted by the following proee. 1) ) 3) 4) The parametri loudpeaker emit the yllable word. Mi. 1 and Mi. oberve the audible ound and reord that. The ubjet liten to the reorded audible ound with a headphone. The ubjet anwer the yllable word. The yllable word inlude vowel and ononant. The peeh artiulation i higher when the audible ound i reprodued with the high ound quality. Therefore, the rate of orret anwer in the audio pot i higher, and that out of the audio pot i lower when the audio pot i formed with propoed method. In addition, the rate of orret anwer i higher when the harmoni ditortion our by the differene tone between the two frequeny omponent inluded the ideband wave under the ondition of emitting the ideband wave without the arrier wave. Thi i beaue the harmoni ditortion have the frequeny omponent imilar to the original audible ound. However, the harmoni ditortion are the lower ound quality. Thu, we expet that the rate of orret anwer in the audio pot i higher and out of the audio pot i lower. In addition, the rate of orret anwer with emitting the ideband wave without the arrier wave i lower than emitting the ideband and arrier wave. Figure 6(a) ~ (d) how the reult of the experiment for the peeh artiulation of the demodulated audible ound. The ondition in Fig.6 are indiated a follow: Proeeding of Meeting on Aouti, Vol. 19, (013) Page 6

7 Matui et al. CM : the onventional method emitting the AM wave PM1 : the propoed method emitting the arrier and ideband wave PM : the propoed method emitting the arrier and divided ideband wave SB : the propoed method emitting the ideband wave SBH : the propoed method emitting the higher frequeny divided ideband wave SBL : the propoed method emitting the lower frequeny divided ideband wave From Fig. 6(a) ~ (d), we onfirmed that the rate of the orret anwer in the vowel i 90 % and that in the ononant i 50 %, with the ondition PM1. The rate of the orret anwer at the Mi. 1 with the ondition PM1 are higher than that at the Mi. with the ondition PM1. Therefore, we onfirmed that the audio pot i formed with the propoed method. On the other hand, the rate of the orret anwer with the ondition PM1 are lower than that with the ondition CM. It how that the peeh artiulation of the demodulated audible ound with the ondition PM1 i wore than that with the ondition CM. The rate of the orret anwer in the vowel i 40 % and that in the ononant i 0 %, with the ondition SB. It how that the harmoni ditortion our by the differene tone between the two frequeny omponent inluded in the ideband wave. The rate of the orret anwer with propoed method emitting the ideband wave with the band-diviion a ondition SBH and SBL are lower than the rate of the orret anwer emitting the ideband wave without the band-diviion a ondition SB at Mi.1. It how that the propoed method emitting the ideband wave with the band-diviion i effetive for reduing the harmoni ditortion in the audio pot. However, the rate of the orret anwer with the ondition PM are lower than the rate of the orret anwer without the band-diviion PM1. Thu, it i neeary to arry out more examination about improvement of the ound quality. (a) Propoed method with non-divided ideband wave (b) Propoed method with divided ideband wave FIGURE 5. Experimental environment in the ubjetive evaluation for evaluating the peeh artiulation TABLE 3. Experimental ondition in the ubjetive evaluation for evaluating the peeh artiulation Sampling frequeny 96 khz Quantization 16 bit Carrier frequeny 40 khz Ambient noie level (L A ) 36 db Sound oure Japanee yllable word ( peaker * 10 word) Dividing frequeny f t 1 khz Subjet 5 peron Proeeding of Meeting on Aouti, Vol. 19, (013) Page 7

8 Matui et al. (a) The reult in the vowel at Mi. 1 (b) The reult in the ononant at Mi. 1 () The reult in the vowel at Mi. (d) The reult in the ononant at Mi. FIGURE 6. Experimental reult in the ubjetive evaluation for evaluating the peeh artiulation CONCLUSIONS The parametri loudpeaker reprodue an audible ound in the partiular area that i alled audio pot. However, refletion and interept by emitted ound beome evere problem. Thi i beaue refletion and intereption lead to an invaion of privay. In thi paper, we propoed the deign method of the audio pot with eparating emiion of the arrier and ideband wave. When, parametri loudpeaker emit ideband wave, the harmoni ditortion may our by the differene tone between two frequeny omponent inluded in the ideband wave. Thu, we alo propoed the method of reduing the harmoni ditortion uing divided ideband wave with band-divided. We arried out the objetive evaluation experiment to meaure the SPL of the demodulated audible ound. In addition, we arried out the ubjetive evaluation experiment to evaluate the peeh artiulation of the demodulated audible ound. A a reult, we onfirmed that that audio pot wa formed in the area inluding both arrier and ideband wave with the propoed method. In addition, we onfirmed that the propoed method with the divided ideband wave i effetive for reduing the harmoni ditortion. Therefore, we onfirmed the effetivene of the propoed method. In future work, we will have to improve the ound quality and the SPL of the demodulated audible ound uing more parametri loudpeaker. ACKNOWLEGEMENT Thi work wa partly upported by Grand-in-Aid for Sientifi Reearh, funded by MEXT, Japan. REFERENCES 1. P. J. Wetervelt, Parametri aouti array, J. Aout. So. Am., vol. 35, no. 4, pp , (1963).. H. M. Merklinger, Improved effiieny in the parametri tranmitting array, J. Aout. So. Am., vol. 58, no. 4, pp , (1975). Proeeding of Meeting on Aouti, Vol. 19, (013) Page 8

9 Matui et al. 3. C. Shi and W. S. Gan, Development of parametri loud-peaker: a novel diretional ound generation tehnology, IEEE Potential, vol. 9, no. 6, pp. 0-4, (010). 4. M. Yoneyama, J. Fujimoto, Y. Kawamo and S. Saabe, The audio potlight: An appliation of nonlinear interation of ound wave to a new type of loudpeaker deign, J. Aout. So. Am., vol. 73, no. 5, pp , (1983). 5. T. Kamakura, M. Yoneyama and K. Ikegawa, Development of parametri loudpeaker for pratial ue, Pro. 10 th International Sympoium on Nonlinear Aouti, pp , (1984). 6. T. Kamakura, Two model equation for deribing nonlinear ound beam, Japanee Journal of Applied Phyi, 43(5B), pp (004). Proeeding of Meeting on Aouti, Vol. 19, (013) Page 9