Auditory profile analysis: frequency, phase, and Weber's law

This paper reports three separate experiments on different aspects of performance in auditory profile analysis. The first experiment deals with the effects of the frequency and position of an increment in a single component of a multitonal complex. The general results indicate that detection of the signal is easier for components in the mid-frequency range (around 1000 Hz) independent of signal position within the complex. The second experiment investigates the effects of relative phase of the individual components of the complex. Regardless of the number of components, our results indicate that phase has very little effect, even when different phases are selected for each presentation. The third experiment compares the detection of an increment in intensity of a single component, the traditional Weber fraction experiment, and conditions where additional components are present, a profile experiment. The detection of the increment is measured as a function of the level of the standard. The single-tone condition shows the usual near miss to Weber's law whereas the multitone condition does not. In addition, threshold for the increment is better for the multitone condition than for the single tone condition for levels of the standard up to 70 dB SPL. This last result is investigated for ten observers, five of whom were experienced in profile tasks and five of whom were not. Using a low level standard, the five experienced observers replicate the results described above. The inexperienced observers show the opposite result. On average, they are better able to detect the increment in the single-component condition.