Growth of Noisiness for Tones and Bands of Noise at Different Frequencies

Abstract

Judgment tests have been conducted to measure the growth of noisiness as a function of sound-pressure level (SPL) for tones and bands of noise over a range of frequencies and reference SPL's. Adjustment-test results at 1000 Hz showed a mean value of 11.5 dB per doubling or noisiness except for the lowest reference level (50 dB SPL) where the mean was 16.7 dB. Magnitude-estimation results yielded values between 20 and 27 dB per doubling of noisiness. The specific value used for the growth of noisiness did not significantly affect the calculation of relative PNL values. Equal noisiness contours were obtained for: (1) pure tones in a free field, (2) 13-oct bands of noise in a free field, (3) 13-oct bands of noise in a diffuse field, (4) 1-sec and 4-sec stimulus durations, and (5) for loudness and noisiness instructions. No significant differences were found for the latter two conditions. [Research supported by the Federal Aviation Administration.]