Hannes Musch

Loudness Near Threshold and the Loudness-Growth Function at Low Sensation Levels

MS Thesis
Date: August 26, 1997

Abstract:

This thesis attempts to determine the loudness at absolute threshold and to estimate the form of the loudness-growth function at low levels in normal-hearing listeners. To this end, loudness balances between a pure tone and complex tones consisting of four or ten tonal components were obtained. Based on the loudness balances, loudness-growth functions were constructed for the individual listeners. The loudness-growth functions were modeled as a modified power law. To account for component interaction in the tone complexes, the model included a loudness-reduction function whose form was roughly consistent with predictions by an excitation-pattern model. The results show that for five of the six listeners tested loudness at threshold is greater than zero. Modeled loudness-growth functions show slopes (in log(loudness) vs. log(intensity) coordinates) of 0.2 at 40 dB SL (mean across all listeners) and 1.37 at 0 dB SL (mean across the five listeners who could produce loudness matches with component levels at threshold). The slope at threshold qualitatively confirms loudness-growth models which assume loudness at threshold to be greater than zero and loudness to grow proportionally with sound intensity, although the present results indicate that loudness may grow slightly faster than proportionally with sound intensity near threshold.

Committee:

Prof. S. Buus (advisor)
Prof. M. Florentine
Prof. D.H. Brooks