Bias-Free Loudness Judgments for White Noise

Abstract

Loudness judgments are especially sensitive to experimentally induced biases. An earlier study [R. M. Warren, “Elimination of Biases in Loudness Judgments for Tones,” J. Acoust. Soc. Amer. 48, 1397–1403 (1970)] eliminated known biasing factors (by using only single judgments from large groups of unpracticed subjects and employing symmetrical response ranges), and found that half loudness (12L) for tones corresponded to half sound-pressure level (12P) or 6-dB attenuation. The present study extended this procedure to white noise, using 12 separate groups of 30 subjects. It was found that 12L = 12P from about 45 through 90 dB. This relation held for both loudspeaker and diotic headphone stimulation. These results are in agreement with the theory which considers that subjective magnitude estimates for sounds are based upon familiarity of the listener with the relation between level of stimulation and distance from the source. Half L corresponds to the effect of doubling distance and hence corresponds to 12P (or 12 sound energy). It is suggested that the sone scale, which considers 12L = 0.32P (or 10-dB attenuation), reflects the systematic influence of known biasing effects.