Vol.2 No.4 2010

37/68

Research paper : How the reliable environmental noise measurement is ensured (R. Horiuchi)−267−Synthesiology - English edition Vol.2 No.4 (2010) Sound pressure level: Sound pressure is normally expressed as sound pressure level because hearing ability of normal person ranges widely. Sound pressure level Lp is defined by the following equation: where p is rms value of sound pressure and p0 is reference sound pressure of 20 Pa which is minimal audible value for a sinusoidal signal of 1 kHz.Traceability: Traceability of a measuring instrument is ensured if the reasons for its uncertainty analysis can be deduced from the national standards.Pressure sensitivity: Pressure sensitivity is ratio of the open-circuit output voltage of the microphone to the sound pressure uniformly applied to the diaphragm.FFT analyzer: FFT analyzer is an instrument to calculate FFT (Fast Fourier Transform) of the input signal and it is useful for frequency analysis of acoustic signal.Wire meshed floor: Wire meshed floor is composed of crossed wires, tense enough for persons to walk on. Indirect sound can be decreased because sound wave passes through the squares of grillwork.Free-field sensitivity: Free-field sensitivity is ratio of the open-circuit output voltage of the microphone to the sound pressure that would exist at the position of the microphone in the absence of the microphone for plane progressive sound field.Introduction of the microphone into the sound field changes sound pressure at the position of the microphone because sound wave is reflected or diffracted by the microphone. Free-field sensitivity of a laboratory standard microphone is essential for secondary calibration of acoustic measuring instruments to get precise sound pressure which is not influenced by the existence of the microphone.Ratio of free-field sensitivity to pressure sensitivity depends on the shape of microphone housing and acoustic characteristics of the diaphragm. Thus specific type of microphones has particular value of the ratio. Measured ratio and its uncertainty are given for laboratory standard microphones[35].Quality system: Quality system requires documenting the process of quality control based on the standard concerned to ensure the reliable calibration results. It consists of grounds for uncertainty analysis, practical calibration procedures, handling of instruments, personnel and calibration records.Term 1. Term 2.Term 3.Term 4.Term 5.Term 6.Term 7.TerminologyLp = 10log p02p 2D. R. Raichel: The science and applications of acoustics, AIP Press, New York (2000).JIS Z 8106, International Electrotechnical Vocabulary Chapter 801: Acoustics and electroacoustics (2000).H. Tachibana and H. Yano: Measurement Methods for Environmental Noise and Building Acoustics, Corona Publishing Co., Tokyo (2004) (in Japanese).IEC 61094-4, Measurement microphones Part4: Specifications for working standard microphones (1995).JIS C 1509-1, Sound level meters Part1: Specifications(2005).JIS C 1509-2, Sound level meters Part2: Pattern evaluation tests (2005).JIS C 5515, Standard condenser microphones (1981).IEC 61094-1, Measurement microphones Part1: Specifications for laboratory standard microphones (2000).T. Takahashi and H. Miura: New calibration system for laboratory standard condenser microphones at ETL, Proc. of technical committee on engineering acoustics, EA-80-37 (1980) (in Japanese).T. Takahashi and H. Miura: Accuracy on coupler calibration of laboratory standard condenser microphones, Researches of Electrotechnical Laboratory, 902, (1990) (in Japanese).S. Sato and T. Fujimori: Treatment of measurement uncertainty at compliance judgment of acoustic measurement instruments, Journal of Acoustical Society of Japan, 59(10), 628-633 (2003) (in Japanese).JIS Z 8732, Determination of sound power levels of noise sources using sound pressure−Precision methods for anechoic and hemi-anechoic rooms (2000).JIS Z 8736-1, Determination of sound power levels of noise sources using sound intensity Part1: Measurement of discrete points (1999) (in Japanese).JIS C 1515, Sound calibrators (2004).IEC 61094-2, Measurement microphones Part2: Primary method for pressure calibration of laboratory standard microphones by the reciprocity technique (2009).R. Horiuchi, T. Fujimori and S. Sato: Development of a laser-pistonphone for an infrasonic measurement standard, 4th joint meeting of acoustical society of Japan and acoustical society of America, 4aEA4, (2006).IEC 61094-6, Measurement microphones Part6: Electrostatic actuators for determination of frequency response (2004).R. Horiuchi, T. Fujimori and S. Sato: Coupler calibration system of standard condenser microphones with a higher electrical accuracy, Bulletin of the Electrotechnical Laboratory, 60(7), 7-16 (1996) (in Japanese).G. S. K. Wong and T. F. W. Embleton: AIP Handbook of Condenser Microphones: Theory, Calibration and Measurements, AIP press, New York (1995).R. Horiuchi, T. Fujimori and S. Sato: Instability of the voltage transfer function for an MR103 microphone in a coupler calibration technique, Journal of Sound and Vibration, 266-5, 981-991 (2003).R. Horiuchi, T. Fujimori and S. Sato: Causes of measurement error of voltage attenuation between two standard condenser microphones in coupler calibration system Part7, Proc. of Autumn Meeting of Acoustical Society of Japan, 643-644 (2001) (in Japanese).R. Horiuchi, T. Fujimori and S. Sato: Uncertainty analysis for pressure sensitivities of laboratory standard microphones, Acoustical Science and Technology, 25(5), 354-363 (2004).[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]References

※このページを正しく表示するにはFlashPlayer9以上が必要です