The effect of the preceding masking noise on monaural and binaural release from masking

The auditory system uses various signal properties to separate a target signal from background noise. When a target tone is preceded by a noise, the threshold for target detection can be increased or decreased depending on the type of a preceding masker. The effect of the preceding masker on the following sound can be interpreted as stream formation. The effect of stream formation is assumed to be either the result of adaptation at a low-level or high-level auditory processing. In an attempt to disentangle these, we investigated the time constant of the underlying process of adaptation by varying the length of the preceding masker. We designed stimuli consisting of the preceding masker and the following masked tone. Each stimulus induces various stream formation, affecting following target detection or masking release. Target tone was presented in comodulated masking noise and with interaural phase difference (IPD), inducing comodulation masking release (CMR) and binaural masking level difference (BMLD), respectively. We measured CMR and BMLD when the length of preceding maskers varied from 0 (no preceding masker) to 500 ms. We postulate that if the adaptation is dominated by high-level auditory processing, both CMR and BMLD will be affected by an increase in the length of the preceding masker. Results showed that CMR was more affected with longer preceding maskers from 100 ms to 500 ms compared to shorter maskers. On the contrary, the preceding masker did not affect the BMLD. Based on the results, we suggest that the adaptation to a preceding masking sound may arise from a low-level (e.g., cochlear nucleus, CN) rather than the temporal integration by the high-level auditory processing. ### Competing Interest Statement The authors have declared no competing interest.