The role of spectral detail in the binaural transfer function on perceived externalization in a reverberant environment

Abstract

Individual binaural room impulse responses (BRIRs) were recorded at a distance of 1.5 m for azimuth angles of 0 and 50 in a reverberant room. Spectral details were reduced in either the direct or the reverberant part of the BRIRs by averaging the magnitude responses with band-pass filters. For various filter bandwidths, the modified BRIRs were convolved with broadband noise and listeners judged the perceived position of the noise when virtualized over headphones. Only reductions in spectral details of the direct part obtained with filter bandwidths broader than one equivalent rectangular bandwidth affected externalization. Reductions in spectral details of the reverberant part had only little influence on externalization. In both conditions, externalization was not as pronounced at 0 as at 50 . To characterize the auditory processes that may be involved in the perception of externalization, a quantitative model is proposed. The model includes an echo-suppression mechanism, a filterbank describing the frequency selectivity in the cochlea and a binaural stage that measures the deviations of the interaural level differences between the considered input and the unmodified input. These deviations, integrated across frequency, are then mapped to a value that corresponds to the perceived externalization.

The Role of Reverberation and Magnitude Spectra of Direct Parts in Contralateral and Ipsilateral Ear Signals on Perceived Externalization

“…A previous study in [17] investigated the role of spectral details in direct parts of BRIRs on perceived externalization. For that, different levels of smoothing were achieved by using gammatone filters with various bandwidth factors B (bandwidth factors are the values relative to one equivalent rectangular bandwidth (ERB) [25]) ranging from 0.316-63.1.…”

“…Based on the two studies (cf. [8,17]) mentioned above, it could be concluded that the spectral details in the direct sound are important for perceived externalization of virtual sound sources when reverberation is present. However, relatively little is known about whether the spectral details in direct parts of ipsilateral and contralateral ear signals have the same influence on perceived externalization.…”

“…Hassager et al [17] studied the role of spectral details in BRIRs on perceived externalization. The magnitude spectra in the direct and reverberant part of BRIRs were smoothed by using gammatone filters with different bandwidths.…”

“…This study aimed to investigate the influence of (a) smoothing the magnitude spectra of direct parts and (b) removing the reverberation, in contralateral and ipsilateral ear signals on perceived externalization. In the studies of Catic et al [13] and Hassager et al [17], the reverberation and magnitude spectra of direct parts were modified for both ear signals. In order to study the influence of these two cues in contralateral and ipsilateral ear signals on perceived externalization, the reverberation and magnitude spectra of direct parts in each ear signal were manipulated separately in the present study.…”

Effects of hearing-aid dynamic range compression on spatial perception in a reverberant environment

“…Individual BRIRs were measured from the loudspeakers placed at the azimuth angles of 0, 30, 150 180, 240, and 300 deg. The BRIR measurements were performed as described in Hassager et al (2016). The microphones were placed at the ear-canal entrances and were securely attached with strips of medical tape.…”