Masked DL for pitch memory.

Abstract

This paper reports differential sensitivity for pitch memory of pure tones as frequencies from 0.125 to 2 kcps are progressively raised above white noise adjusted to a 50% masking effect at the 45-dB sensation level of the tone. The Weber fraction (DF/F) improves with some negative acceleration through 2 kcps both in favorable and in unfavorable masking levels, but below about 0.5 kcps the sensitivity progressively deteriorates. The Weber fraction is related linearly to loudness, the loudness of tones in noise being specified by balancing to a 1-kcps tone in quiet. However, tones in noise exhibit poorer Weber fractions than tones at the same loudness but with no mask. Thus, the noise introduces a brake on sensitivity not only by loudness reduction but by an additional mechanism. The number of distinguishable pitches between 0.125–2 kcps is reduced from 548 for tones in quiet at 45 dB sensation level, to only 170 for tones in noise at a very unfavorable (signal-to-noise) S/N ratio (tones 5 db over the 50% masking point.)