ASA 125th Meeting Ottawa 1993 May

5aNS2. Testing the response of personal noise exposure meters (noise dosimeters) to impulse-like signals using a laboratory reference noise dosimeter and a theoretical model (after ANSI S1.25-1978).

David J. Evans

Acoust., Mass & Vib. Group, NIST, Bldg. 233, Room A149, Gaithersburg, MD 20899-0001

A laboratory reference noise dosimeter consisting of a measuring amplifier and instrument controller was assembled and characterized. A theoretical expression was obtained for the A-weighted, rms-detected output of a noise dosimeter assuming an input signal equal to that of a tone-burst sequence containing bursts comprised of an integral number of cycles of a sine wave. The output of the theoretical detector was numerically integrated to obtain percentage criterion exposure or time-weighted equivalent level. Equivalent levels were measured and calculated for each sequence in a set of tone-burst sequences with burst durations of 1 to 1000 cycles and crest factors of 4.8 to 30 dB. The agreement between equivalent levels obtained using the reference dosimeter and theoretical calculations was typically +0.1 dB. The results of these measurements and calculations were then used as a basis of comparison for testing the response of commercially available noise dosimeters to a subset of the tone-burst sequences. [Work supported by OSHA.]