Bastian Epp

Publications

• 2.22

  Impact points

  Superposition of masking releases.

  Bastian Epp, Jesko Verhey

  Journal of computational neuroscience. 12/2008;

  We are constantly exposed to a mixture of sounds of which only few are important to consider. In order to improve detectability and to segregate important sounds from less important sounds, the auditory system uses different aspects of natural sound sources. Among these are (a) its specific location... [more] We are constantly exposed to a mixture of sounds of which only few are important to consider. In order to improve detectability and to segregate important sounds from less important sounds, the auditory system uses different aspects of natural sound sources. Among these are (a) its specific location and (b) synchronous envelope fluctuations in different frequency regions. Such a comodulation of different frequency bands facilitates the detection of tones in noise, a phenomenon known as comodulation masking release (CMR). Physiological as well as psychoacoustical studies usually investigate only one of these strategies to segregate sounds. Here we present psychoacoustical data on CMR for various virtual locations of the signal by varying its interaural phase difference (IPD). The results indicate that the masking release in conditions with binaural (interaural phase differences) and across-frequency (synchronous envelope fluctuations, i.e. comodulation) cues present is equal to the sum of the masking releases for each of the cues separately. Data and model predictions with a simplified model of the auditory system indicate an independent and serial processing of binaural cues and monaural across-frequency cues, maximizing the benefits from the envelope comparison across frequency and the comparison of fine structure across ears.
• 1.52

  Impact points

  Influence of noise type, degree of comodulation and interaural phase difference on the combined monaural and binaural masking release.

  Bastian Epp, Jesko Verhey

  The Journal of the Acoustical Society of America. 06/2008; 123(5):3051.

  Several masking experiments have shown that the auditory system is able to use coherent envelope fluctuations of the masker across frequency within one ear as well as differences in interaural disparity between signal and masker to enhance signal detection. The two effects associated with these abil... [more] Several masking experiments have shown that the auditory system is able to use coherent envelope fluctuations of the masker across frequency within one ear as well as differences in interaural disparity between signal and masker to enhance signal detection. The two effects associated with these abilities are comodulation masking release (CMR) and binaural masking level difference (BMLD). The aim of the present study was to investigate the combination of CMR and BMLD. Thresholds of a sinusoidal signal were measured in a flanking band paradigm, i.e., in the presence of several narrowband noise maskers, (i) for two noise types (Gaussian and multiplied noise), (ii) various degrees of comodulation, and (iii) various interaural phase differences (IPD) of the signal. Thresholds decreased as the signal IPD increased and decreased as the masker comodulation increased. For both noise types, the maximum CMR was about 10 dB and the maximum BMLD was about 14 dB. Thresholds where monaural and binaural cues were present showed an addition of the single effects, i.e., a maximum masking release of 24 dB. A simplified model of the auditory system assuming a serial alignment of the across-frequency and the binaural processing stages is able to reproduce the dataset.