The effect of hand-held radio operation on audio dosimeters

Six models of audio dosimeters from five manufacturers were tested to determine the effect of radio frequency (r-f) interference caused by the operation of hand-held radios near the dosimeters on the measured average sound pressure level in a controlled noise field. Exposures were in a reverberant chamber at levels of 36, 80, and 92 dBA to an octave of noise centered at 1 kHz. Two walkie-talkie type radios, one operating at 160 mHz and the other operating at 460 mHz were used to generate the r-f field. The radios were operated on two duty cycles (2 or 3 cycles/min) during the recording period. Reported measures, such as average sound pressure level and peak sound pressure level, were compared for each noise exposure condition with and without operation of the hand-held radio. The results indicate that all makes and models of the dosime-ters that were tested gave false readings under some condi-tions. These values always exceeded the reading in the noise alone control condition and varied by as much as 45 dB above the “true” level. Because each dosimeter behaved differently—including different samples of identical models—it was not possible to develop a correction factor for radio interference. Rather, steps are recommended to help users identify potential r-f contamination on dosimeter performance in the field.