Spectral shape discrimination with random variations in background dimensions.

Abstract

The current research investigated the ability of observers to discriminate a global property of a complex stimulus−the slope of the linear spectral envelope as a function of variation in two background dimensions: fundamental frequency (thus pitch) and a ripple filter function imposed upon the spectral envelope. Two dimensions are judged to be integral if a significant decrement in slope discrimination performance occurs due to a roved relative to fixed background dimension. All experiments used a XAB task with roving overall spectral level within trials to eliminate intensity cues. A significant decrement due to roving fundamental frequency suggests that the linear spectral envelope is integral with fundamental frequency. In contrast, a strikingly small decrement due to roving the ripple filter function suggests that the linear spectral envelope is more easily separable from the ripple filter function than from fundamental frequency. Therefore, the global property of slope of the linear spectral envelope may be unitized with pitch, but is relatively independent of a modest (4-dB) variation in the actual spectral envelope. [Work supported by NSF.]