Effects of Background Noise upon Perceived Noisiness

Cross‐modality tests, matching the apparent intensity of a 100‐Hz vibration to the noisiness of 13‐oct bands of noise, have been conducted to measure the effects of background noise upon judged noisiness. The growth function for noisiness behaves like a modified power function of the form ψ = k(In − I0n), where ψ is noisiness, I is the intensity of the stimulus, I0 is the threshold intensity, and k and n are constants that depend upon frequency. A calculation scheme has been developed that reduces the sound‐pressure level of each 13‐oct band by an amount dependent upon the signal‐noise/background‐noise ratio. For signal‐noise/back‐ground noise band‐level ratios of greater than 65 dB, the band correction is equal to 0. For realistic background spectra and signal‐noise/background‐noise over‐all level ratios of 40 dB, the total correction is approximately 3 PNdB. [Research supported by the Federal Aviation Administration.]