CONTRIBUTION REGARDING NOISE MEASUREMENT ACOUSTIC PROCEDURES ON BOARD

Transcription

1 SISOM 2013, Acoustics and Robotics, Bucharest May CONTRIBUTION REGARDING NOISE MEASUREMENT ACOUSTIC PROCEDURES ON BOARD Victor POPOVICI 1, Claudia BORDA 1, Delicia ARSENE 1, Larisa BUTU 1, Marinela MARINESCU 1, Mihai ARSENE 2 1 University POLITEHNICA of Bucharest, 2 SC AFICO SA, Bucharest, arsenemihai2008@yahoo.co.uk Work aims is the identification and evaluation the parameters that define and contribute to noise on board. Noise measurement procedures are presented for on board air noise. In order to determine how it is affected staff as well as underwater level of noise emitted by the ship, the data obtained are evaluated and compared with noise levels imposed by European legislation. Keywords: noise, procedure, acoustic field, Sound Level Meter 1. INTRODUCTION In order to perform measurements to determine the level of noise on board vessels were developed working procedures and have been proposed also appropriate work equipment. In this paper were performed acoustic field measurements to determine existing level of noise, the extent to which it affects the staff, the compliance standards and provisions relating to environmental protection. 2. NOISE MEASUREMENT PROCEDURES Noise measurement procedures set out in the paper contributes to the control of acoustic energy at locations which are sensitive to the level or quality of noise. To provide a coherent framework in the case within which measurement in different locations, can be inter-related, are presented the following basic conceptual model of the emission, propagation and noise pollution potential: - acoustic energy is emitted by specific components of equipment or machinery; - energy radiation pattern can be generally approximated by assuming that the total noise power of a particular item is emitted from a primary source located in the approximate center of the component; some variations of this model may be necessary for the sources extensible to the intercept close positions; - radiation pattern of acoustic energy can generally be seen as being isotropic (eg energy radiates equally in all directions) except there is evidence to the contrary; - acoustic energy decrease with distance from the source directly proportional to the square of the distance between the source point and any position effectively intercept; - airborne noise paths through the air are relatively straight and may be subjected to various modifications such as absorption and atmospheric refraction, which are becoming more and more significant with increasing distance from the source; - noise can be modified by the presence of sufficiently large objects that can reflect or absorb the noise; this can lead to increases or decreases in sound pressure level associated with a particular sound position; - noise levels are measured with acqiusiton devices and processed with specialized software.

2 Victor POPOVICI, Claudia BORDA, Delicia ARSENE, Larisa BUTU, Marinela MARINESCU, Mihai ARSENE MEASUREMENT OF ACOUSTIC FIELD PARAMETERS ON BOARD In this paper are presented measurements of the acoustic field on board conducted to establish existing level of noise, the extent to which it affects staff and the compliance with standards and provisions regarding environmental protection. To measure the level of noise in the air (on board) have considered the following requirements: - noise levels will be measured, analyzed and interpreted in accordance with STANAG acoustic field of surface vessels; - measuring equipment must be in accordance with IEC 651: Sound level meters, IEC 804: Sound level meters and allow integrating sound pressure measurements in the band 31.5 to 8000 Hz (or Hz); - noise is measured in decibels on scale A (reference level 2x10-5 Pa). Noise spectrum must be registered by measuring sound pressure levels in octave bands with medium frequencies between 31.5 and 8000 Hz. Laboratories measure shipboard acoustic field parameters are mobile structures having in composition: prepolarized condenser microphones, sound level meters, devices of filters 1/1 and 1/3 octave, calibrators, spectrum analyzer, signal generator, laptop, data acquisition plaque, specialized software, and so on, with specific characteristics of the environment and parameters measurement and complying the standards specified in the preceding paragraph. To determine the level of noise on board were conducted noise measurements aboard NS "Mircea" in accordance with STANAG Measuring instruments used is given in Table 1. Table 1. Equipment used for measurement of the noise level on board NS "Mircea" Name Manufacturer Type Precision Sound Level Meter Brüel&Kjær 2203 Microphone Adapter Brüel&Kjær UA0196 Condenser Microphone Brüel&Kjær 4165 Pistonfon Brüel&Kjær 4220 Calibrator Brüel&Kjær 4223 Data acquisition and processing Bruel&Kjaer 3560D system Bruel & Kjaer 3560D Connection cable Brüel&Kjær R 6868 Power amplifiers Bruel & Kjaer Bruel&Kjaer 2713, , 2716 Computer Software Bruel&Kjaer Pulse 12 Measuring system, sound level meter microphone adapter - acquisition plaque - computer was calibrated using standard pistofon Description of the measuring equipment used - Portable sound level meter model Software Applications: for the noise level measurement - BZ7222; Frequency Analysis - BZ7223; Recording (Logging) - BZ7224; Recording noise - BZ7226; The 2250 may contain an set of software modules, including frequency analysis, recording software (Logging) and registration of the measured signal (Figure 1).

3 193 Contribution Regarding Noise Measurement Acoustic Procedures On Board Figure1. Portable sound level meter model Use: monitoring and assessment of environmental noise;assessment of noise at the workplace;option for hearing protection;product quality control;class 1 sound measuring current international standards;real-time sound analysis in 1/1 and 1/3-octave bands;the review of the data stored for subsequent analysis measurements;use the text and the voice for setting the measurements;use settings in moment of registration and measurement of sound. Features: color display with specific high resolution large sized quick response when pressed; USB interface standard PC; dynamic Measuring band 120 db; frequency band linear measuring 3 Hz - 20 khz. Reviewing data and spectra for further analysis. recording of the sound and of the measured signal; customizing the measurement of the screen and of the operating procedures; software package included for installation, archiving, export and reporting; automatic detection and correction of the protection screen; robust, protected against atmospheric agents in the environment. - Portable model 2260 Investigator Sound Level Meter: The device is portable, has a very sensitive microphone, able to perceive the finest sounds (Figure 2.). The device measures the noise levels up to 130 db, displays real-time weighted values A, B, C or L, allows the display of the distribution by levels of the noise and real-time plotting FFT spectrum for the respective measurement. Machine interface allows using cursors, determine the noise level at certain frequencies and thus immediately identify many problems. Built on a PC-like architecture, has a large capacity internal memory for saving measurements and reviewing them at any time (in system folders and files), can be connected to a personal computer for further analysis files saved with advanced programs, such as a room acoustics simulation and spectral analysis. Use: monitoring and assessment of environmental noise;assessment of noise at the workplace; option for hearing protection; real-time sound analysis in 1/1 and 1/3-octave bands; the review of the data stored for subsequent analysis of the measurements performed. Features: Microphone: High sensitivity (-26dB); Measuring range: 80 db, anywhere between 0 and 130 db levels; Frequency range: 6.3 Hz - 20 khz; Detectors: in parallel weighting A and C or L, with specific correction filters included to eliminate disturbances introduced by other sources or protection from the wind; Measurement modes: manual, automatic (on a specific time interval, autosave), sequence (repeat a measurement up to 9999 times), recording (measurement of several steps in a defined time); File Management: allows you to save, recall, edit files, grouping them in folders, attaching labels; Storage: 32 MB internal memory, or on external memory card, can connect to PC to transfer information; Display: LCD screen 192 x 128 internal light and high visibility; Power supply: 6 x LR14 1.5V batteries (life time 1 to 9 hours of continuous operation) or external source.

4 Victor POPOVICI, Claudia BORDA, Delicia ARSENE, Larisa BUTU, Marinela MARINESCU, Mihai ARSENE 194 Figure Investigator Sound Level Meter portable model. The values of the total noise levels measured in the different compartments of the vessel, in normal marching on the sea are shown in Table 2. Point of measurement Value provided STANAG 4293 march under normal conditions Value [db] Curve NZE value provided RNR [db] Measured value [db] Machinery compartment between DG Bb and central Engine room near MP Command deck (near steering) Command deck (in front of the suction aft) Command deck (between the chimney and the suction bow Teuge (near steering) Teuge (near the anchor winch) Quarterdeck (PD) Quarterdeck (Tb) Room of Maps (Bb) Room of Maps (PD) Room of Maps (Tb) Dining room MT Dining room officers Cabin no. 8 Situated in Bb The measurements in the band of 1/1 octave were performed in the following cases: When the measured values shown in Table 2., Exceed the maximum standard STANAG for a measurement position in a room with special working conditions; for all postures that speech intelligibility is important. Therefore, for all measuring points shown in Table 1, there was performed signal analysis in octave bands listed above. For each measuring point were presented: the "frequency noise level" in the frequency band Hz (Figure 3); features "noise levelfrequency" in octave bands with specific center frequencies in the range from 31.5 to Hz, (Figure 4); RMS value of the noise level in each frequency band of 1/1 octave; Maximum the noise level in each frequency band of 1/1 octave; NZE feature for each point of measurement (Figure 5); maximum value of NZE; the speech interference level (NIV). For frequencies where Lmax is at least 10 db higher than LRMS separate spectral analysis was done. NIV was an average sound pressure levels with specific center frequencies of 500, 1000 and 2000 Hz.

5 195 Contribution Regarding Noise Measurement Acoustic Procedures On Board Figure 3. The noise level in the frequency band Hz. Figure. 4. Noise level in octave bands with specific center frequencies ranging in the range of from 31.5 to Hz Figure. 5. NZE characteristic for each measurement.

6 Victor POPOVICI, Claudia BORDA, Delicia ARSENE, Larisa BUTU, Marinela MARINESCU, Mihai ARSENE 196 The values of the acoustic environment to be protected is set to the Measuring protocol: Various features of a particular noise generally identified as tonality, impulsiveness, modulation and / or low-frequency components may increase the potential interference. These features tend to increase the noise content of the specific information of the specific noises and thus increase its audibility. Audibility of such noise is also influenced by the environmental noise and the characteristics of the area. non-acoustic factors that may influence subjective audibility and noise pollution potential of a particular noise include subjective value and effectiveness of noise generating activities or any attempt to control noise. adapt to noise, past experience, individual differences and personality can influence the response of a particular listener. Measurement of noise from a specific source is normally carried out at positions near the source where the sound pressure level of noise at source is significantly higher than the sound pressure level from all other noises. This is not a strict requirement that the contribution of other noise that can generally be calculated or measured. The noise measured at a position close enough to provide, in general, a closer representation of the noise emitted by the source. Any characteristics of the noise emission, such as the presence of tonal components and variation in amplitude can be quantified in the measurement of near. Sometimes it is convenient to obtain or calculate the acoustic power (eg acoustic energy emission rate) of a noise source so that sound pressure levels to be set at a variety of locations. Characteristics resulting sound pressure levels can be applied to acoustic power corresponding to the noise source. 4. CONCLUSIONS Noise measurement procedures and the equipment proposed were used for the noise measurements on board, in order to determine the level of noise pollution. The results obtained are comparable with specific those derived from measurements by procedures that are in use but presents an increased susceptibility and comes under specified standards. Measured noise level is within the ranges of values imposed by European legislation. Underwater radiated noise was measured with specific systems and procedures and did not exceed the maximum admissible limits. REFERENCES 1. AMZA Gh, ARSENE M., Underwater antiphase sound generation using virtual laboratory, Scientific Buletin of North University of Baia Mare, Series C, Fascicles Mechanics, Tribology, Machine Manufacturing Technology, ISSN: , CNCSIS Code: 610, Nr.XXVII, mai ARSENE, D., BORDA, C., BUTU,L., MARINESCU, M., POPOVICI, V., ARSENE, M., Experimental research and modeling of the underwater sound in marine environment, Acoustics and Vibrations of Mechanical Structures, AVMS, Timisoara, May POPOVICI, V., ARSENE, D., BORDA, C., BUTU,L., MARINESCU, ARSENE, M., Virtual Laboratory for Underwater Noise Attenuation, TEHNOMUS XVII, 17 th International Conference on New Manufacturing Technology, Suceava, Romania, May, 17-18, ARSENE, M., Study for reducing noise pollution of the marine environment by introducing noise at the acoustic source, Scientific Bulletin, Series C, Electrical Engineering and Computer Science, ISSN , 2012.