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Administrative and Logistics:
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Pressure calibrations (Service ID Nos. 25010C and 25020C) are performed on Type-L one-inch microphones* satisfying the requirements of American National Standard S1.12-1967 (R1977), Specifications for Laboratory Standard Microphones and its impending revision. The microphones submitted for pressure calibration must be suitable for use with the calibrating couplers shown in Figures 6 and 10 of the applicable American National Standard S1.10-1966 (R1986).
* Type-L one-inch is a commercial designation for these microphones.
Further information is contained in the references for acoustic measurements.
Since American National Standards Institute publications S1.10-1966 (R1986) and S1.12-1967 (R1977) were issued, certain types of half-inch diameter precision microphones have attained widespread use. Therefore, NIST has developed procedures (Service ID Numbers 25030C and 25040C) for determining the pressure response levels of half-inch microphones by comparison with NIST-owned Type-L standard microphones, which in turn are calibrated periodically by the reciprocity technique. The technique used, precautions to be observed, and uncertainties of measurement are essentially the same as those given above for one-inch microphones. Significantly different aspects of the procedures for half-inch microphones, such as ground shield configuration, are described in the test report. Since several half-inch laboratory standard microphones have been available for only a relatively short time, their long-term stability has yet to be determined.
Acoustical measurement services are available by special arrangement. These services include extended frequency ranges of calibration, additional data points, measurements at very low sound pressure levels, and calibration of certain pistonphones and acoustic calibrators. NIST has a large general-purpose anechoic chamber available for special calibrations requiring such a facility. The frequency-dependent and position-dependent acoustical performance of this chamber, including extremely low background noise, was carefully controlled during design and construction and is documented in archival journal publications.
Calibration of Pressure and Gradient Microphones, V. Nedzelnitsky, Encyclopedia of Acoustics, Ed. in Chief M. J. Crocker, John Wiley & Sons, Inc., New York, 1869-1879 (1997).
Primary Method for Free-Field Calibration, V. Nedzelnitsky , AIP Handbook of Condenser Microphones, Eds., G. S. K. Wong and T. F. W. Embleton, Am. Inst. of Physics Press, Woodbury, NY, 103-109 (1995).
Laboratory Microphone Calibration Methods at the National Institute of Standards and Technology, U.S.A., V. Nedzelnitsky, AIP Handbook of Condenser Microphones, Eds., G. S. K. Wong and T. F. W. Embleton, Am. Inst. of Physics Press, Woodbury, NY, 145-161 (1995).
Method for Calibration of Microphones, Amer. Natl. Stand. Inst. S1.10-1966 (R1986), New York, NY.
Specifications for Laboratory Standard Microphones, Amer. Natl. Stand. Inst. S1.12-1967 (R1977), New York, NY.
Free-Field Reciprocity Calibration of Microphones, E. D. Burnett and V. Nedzelnitsky, J. Res. Natl. Bur. Stand. (U.S.) 92 (2), 129 (Mar.-April 1987).
Traceability of Acoustical Instrument Calibration to the National Bureau of Standards, V. Nedzelnitsky, Proc. INTER-NOISE 80, II, Dec. 8-10, 1980, Miami, FL, G. C. Maling, Jr., Ed., Poughkeepsie, NY: Noise Control Foundation, 1043 (1980).
Calibration of Laboratory Condenser Microphones, V. Nedzelnitsky, E. D. Burnett, and W. B. Penzes, Proc. 10th Transducer Workshop, Transducer Committee, Telemetry Group, Range Commanders Council, Colorado Springs, CO (June 1979).
Acoustical Properties of the National Bureau of Standards Anechoic Chamber, W. Koidan and G. R. Hruska, J. Acoust. Soc. Am. 64 (2), 501 (Aug. 1978).