Modeling comodulation masking release using an equalization cancellation mechanism

Abstract

This study presents an auditory processing model that accounts for the perceptual phenomenon of comodulation masking release ͑CMR͒. The model includes an equalization-cancellation ͑EC͒ stage for the processing of activity across the audio-frequency axis. The EC process across frequency takes place at the output of a modulation filterbank assumed for each audio-frequency channel. The model was evaluated in three experimental conditions: ͑i͒ CMR with four widely spaced flanking bands in order to study pure across-channel processing, ͑ii͒ CMR with one flanking band varying in frequency in order to study the transition between conditions dominated by within-channel processing and those dominated by across-channel processing, and ͑iii͒ CMR obtained in the "classical" band-widening paradigm in order to study the role of across-channel processing in a condition which always includes within-channel processing. The simulations support the hypothesis that within-channel contributions to CMR can be as large as 15 dB. The across-channel process is robust but small ͑about 2 -4 dB͒ and only observable at small masker bandwidths. Overall, the proposed model might provide an interesting framework for the analysis of fluctuating sounds in the auditory system.

Comodulation Masking Release Determined in the Mouse (Mus musculus) using a Flanking-band Paradigm

“…It increased from a value of between about 4 and 6 dB for a frequency separation of 1 kHz to a value of 18 dB for a frequency separation of 100 Hz. For both frequency differences between FB and OFM, the CMR was slightly smaller for FB positioned above rather than below the signal frequency, a tendency which is also found in humans (e.g., Hall et al 1988;Piechowiak et al 2007). …”

“…In summary, the CMR effect seen in both mice and men might be explained by either the processing of a single envelope that is extracted from a broad range of frequencies (e.g., Berg 1996;Verhey et al 1999;Piechowiak et al 2007) or may result at least partially from the compressive nonlinearities of peripheral auditory filters processing the stimulus (Buschermöhle et al 2007). …”

“…Both the current study and the band-widening study of Weik et al support the hypothesis that the occurrence of CMR in the mouse can be explained on the basis of within-channel cues only. Also, in humans, it has been suggested that the main contribution to the CMR effect stems from processing of within-channel cues (Berg 1996;Verhey et al 1999;Buschermöhle et al 2007;Piechowiak et al 2007).…”

“…Locking of action potentials to the masker envelope, however, still might provide usable cues. The envelope of the composite masker may be dominated by a temporal interaction between both maskers, leading to a beating with a rate depending on the frequency difference between both center frequencies (e.g., Schooneveldt and Moore 1987;Berg 1996;Piechowiak et al 2007). At a frequency separation of 1 kHz, the beating occurs at a mean rate of 1 kHz, while a frequency separation of 100 Hz leads to a mean beating rate of 100 Hz.…”

Interaction of Object Binding Cues in Binaural Masking Pattern Experiments

“…In this approach a weighted sum of modulation filters at the output of off-frequency auditory filters was subtracted from the corresponding modulation filters at the output of the on-frequency filter. In contrast to Piechowiak et al (2007), a multi-auditorychannel version of this approach was used. Since the weighting is essentially based on the energy in the auditory filters it will be referred to as the energy-based AC model in the following.…”