Overview of some recent experiments on pure-tone intensity discrimination

Intensity resolution for 0.5-see bursts of 1000-Hz tones has been measured in quiet as a function of intensity increment for a variety of intensities ranging from absolute threshold to 90 dB SPL using a symmetric 2I-2AFC technique. The results indicate that (1) in the vicinity of absolute threshold, the discriminability of two intensities can be simply predicted from measures of their detectability; (2) resolution per decibel increases with intensity in the range 0–15 dB SL and may attain a local maximum at 15 dB SL; (3) Weber's law appears to be valid only from about 20 to 40 dB SL; (4) at higher intensities, resolution per decibel improves systematically with intensity; and (5) at each intensity, d′(I, I + ΔI) is proportional to log[(I + ΔI)/I] for values of d′ between 0.5 and 2.5. This talk attempts to relate these findings quantitatively to a variety of relevant prior work.