An Investigation of Auditory Fatigue, Especially as Applied to the Determination of Subjective Harmonics
R. H. Nichols, Floyd A. Firestone · The Journal of the Acoustical Society of America · 1939
An investigation has been made of the pattern of fatigue effect (shift in minimum audible threshold) against frequency for a very pure 202 c.p.s. fatiguing tone, for three observers. The fatiguing tone was sounded for about 2 seconds at levels of from 85 db to 116 db about 0.0002 dyne/cm2, and a short test tone was used to determine the threshold at various frequencies, within from 0.15 sec. to about 0.7 sec. after cutting off the fatiguing tone. Special attention was paid to the frequency region around 404 c.p.s. in an effort to determine whether excess fatigue might be caused by the subjective second harmonic. Considerable variability of results among the three observers was found, although each of the three was consistent in his own results. Two observers gave essentially a constant fatigue effect for the fatiguing frequency and higher frequencies over the range tested. The third observer shows a pronounced peak in fatigue effect at the fatiguing frequency (202 c.p.s.), and some indication of a peak at the second harmonic of the fatiguing frequency (404 c.p.s.). This observer is being tested further to determine whether the peak at 404 c.p.s. is due to subjective harmonic or to his minimum audible threshold characteristic.