Intensity discrimination of tone bursts and the form of the Weber function

Abstract

Intensity discrimination functions were determined for tone bursts at four test frequencies: 250, 1,000, 4,000, and 7,000 Hz. Slopes of best-fitting lines (~l in dB SL vs I in dB SL) indicate a "near-miss" to Weber's law at all four frequencies. The use of information provided by harmonics of the stimulus is discussed; it is concluded that-at least for high-frequency tones-such cues are not the basis for the improved acuity found at higher sensation levels.

Weber’s law, the “near miss,” and binaural detection

“…For monaural listening (MrrrSm), every individual listener clearly confirms the finding reported by Schacknow and Raab (1973) with respect to both the magnitudes of the Weber fractions and the slope of the Weber function (Table 1). There is a near miss to Weber's law for monaural listening, with a slope very close to .90.…”

“…For ready comparison with the tabulated results of Schacknow and Raab (1973) and the graphed results of Yost (1972), all of our results are presented for individual subjects and as averages over subjects in two forms. In terms of the vector diagram of Figure I, the Weber fraction, Mil in dB, is computed as 10 10g[(RR -M2)/M 2] and (I + 61)11 in dB is computed as 10 log(RR/M 2).…”

“…Goldberg (1968a, 1968b) have highlighted the problem, calling it the "near miss" to Weber's law, and have shown how it may reflect the compression role of the transduction of stimulus energy (E) to neural counts (fi) by the transform n: == aEP. Using I for stimulus intensity and M for the magnitude of its just discriminable (energy) increment, the fact that empirical plots of AI in dB against I in dB are well fitted by linear functions with slopes of about .90 (the near miss), rather than 1.00 (Weber's law), means that the exponent of the power transform (p) is about .20 rather than unity.Given our understanding of monaural and binaural processes, Schacknow and Raab (1973), reporting confirmation of the monaural near miss for several test frequencies, and Yost (1972), reporting confirmation of Weber's law for hornophasic and anti phasic binaural tones, appear to contradict each other. With homophasic tones, the listener receives identical inputs at the two ears, and it is commonly assumed that detection or discrimination mechanisms for that configuration are the same as for monaural listening.…”

Auditory Intensity Discrimination

“…Unfortunately, the results of this apparently simple test have been contradictory. Schack now and Raab (1973) found the same decrease in the difference limen with increases in base intensity at 250, 1000, 4000, and 7000 Hz. The lower frequencies might be affected by distortion products, but the higher frequencies could not be.…”

Odor magnitude: Coarse vs. fine grain

“…Olfaction's differential sensitivity no longer seems inferior to that of other modalities, including vision and hearing, where k is approximately 10070 (i.e., 0.10) for successively presented stimuli (Mueller, 1951;Schacknow & Raab, 1973). Unacknowledged fluctuations in the stimulus are apparently responsible for olfaction's previous reputation.…”