Auditory Enhancement of Increments in Spectral Amplitude Stems from More Than One Source

Abstract

A component of a test sound consisting of simultaneous pure tones perceptually "pops out" if the test sound is preceded by a copy of itself with that component attenuated. Although this "enhancement" effect was initially thought to be purely monaural, it is also observable when the test sound and the precursor sound are presented contralaterally (i.e., to opposite ears). In experiment 1, we assessed the magnitude of ipsilateral and contralateral enhancement as a function of the time interval between the precursor and test sounds (10, 100, or 600 ms). The test sound, randomly transposed in frequency from trial to trial, was followed by a probe tone, either matched or mismatched in frequency to the test sound component which was the target of enhancement. Listeners' ability to discriminate matched probes from mismatched probes was taken as an index of enhancement magnitude. The results showed that enhancement decays more rapidly for ipsilateral than for contralateral precursors, suggesting that ipsilateral enhancement and contralateral enhancement stem from at least partly different sources. It could be hypothesized that, in experiment 1, contralateral precursors were effective only because they provided attentional cues about the target tone frequency. In experiment 2, this hypothesis was tested by presenting the probe tone before the precursor sound rather than after the test sound. Although the probe tone was then serving as a frequency cue, contralateral precursors were again found to produce enhancement. This indicates that contralateral enhancement cannot be explained by cuing alone and is a genuine sensory phenomenon.

Effects of auditory enhancement on the loudness of masker and target components

“…This gap is within the range known to elicit strong enhancement effects (e.g. Carcagno et al , 2012), and is sufficiently long to avoid potential confusion between the two stimuli. The target and comparison were separated by a relatively long silent gap of 2 s, to reduce any potential interactions between the precursor and the comparison.…”

The salience of enhanced components within inharmonic complexes

“…Given that presenting the precursor contralaterally results in a greater reduction for intensity enhancement than for frequency enhancement (Erviti et al, 2011), in a third condition (with a 0 ms precursormasker delay) the first segment was moved to the right ear, creating a contralateral precursor (FWD:CONTRA). [Refer to Carcagno et al (2012) for more on contralateral enhancement.] Because of the possibility of backward enhancement (Kidd and Wright, 1994), time-reversed versions of the FWD conditions were used, resulting in a masker-plus-target segment followed by a postcursor segment that did not contain the target (BWD).…”

New perspectives on the measurement and time course of auditory enhancement.

“…Despite these large effects, and their clear importance for auditory and speech perception, surprisingly little is known about their underlying mechanisms. Some psychophysical studies have proposed a combination of neural adaptation and lateral inhibition or suppression as an explanation of the enhancement effects (Byrne et al, 2011; Carcagno, Semal, & Demany, 2012; Viemeister, 1980; Viemeister & Bacon, 1982). Other mechanisms might also play a role.…”

“…A recent method used by Demany, Carcagno and colleagues (Carcagno et al, 2012; Carcagno, Semal, & Demany, 2013) overcomes these issues by employing a one-interval task with frequency components that are selected randomly from trial to trial. Their method involves pitch comparisons between a target presented within the masker and a comparison tone presented afterwards.…”