MULTIBAND DETECTION OF ENERGY FLUCTUATIONS

This study sought to characterize the integration of synchronous energ y fluctuations across relatively independent spectral regions. The det ection of four classes of signal was examined where each class of sign al was associated with a change in energy over time. The four signal t ypes were: (1) multicomponent tonal complexes, with each component cen tered in a narrow band of noise; (2) intensity increments in multiple narrow bands of noise; (3) intensity decrements in multiple narrow ban ds of noise; and (4) temporal gaps in multiple narrow bands of noise. Each signal type was examined in a separate experiment, although stimu lus characteristics such as presentation level and frequency location were held constant. Experiment 1 confirmed that the detection of multi tonal complexes masked by narrow bands of noise is linearly related to root N, where N is the number of signal components. Experiment 2 exte nded this to show that, when the signal was an increment in the level of a noise band carrier, threshold continued to be a linear function o f root N, although threshold was about 2 dB higher than for a comparab le tonal signal. Experiment 3 indicated that the detection of a decrem ent in energy in one or more noise bands was relatively poorer in term s of absolute level changes than was the detection of an energy increm ent in the same stimulus. Examination of psychometric functions for de crement detection suggested that performance improved by less than roo t N. Experiment 4 found that gap detection improved with increasing N but by a factor greater than the root N expected on statistical ground s. Examination of the underlying psychometric functions confirmed this effect. The results of these experiments suggest that, for energy inc rements, the auditory system integrates information from across the sp ectrum in a statistically independent manner, at least over the freque ncy range examined here. This does not appear to be the case far the d etection of energy gaps or decrements. (C) 1997 Acoustical Society of America.