Differences between listeners with early and late immersion age in spatial release from masking in various acoustic environments

Abstract

It is well-known that we benefit from binaural hearing when listening to the speech of interest amongst noise, where spatial cues may release our auditory perception from masking. However, this benefit deteriorates with external factors such as the reverberation in the room, as well as internal factors such as our familiarity with the language of interest. The current study examined spatial release from masking (SRM) experienced by listeners with different age of immersion to New Zealand English (NZE) in varying room acoustics. A speech intelligibility test was conducted using an Ambisonic-based sound reproduction system to reproduce speech and noise as if they were produced in a seminar room and a chapel at two distances between the source and the listener: 2 m and 5 m. The rooms differed in reverberation time (RT), and the distances modified the speech clarity (C50). The participants were split into an early immersed group (n= 20), and a late immersed group (n= 37), where the participants in the early immersed group were immersed in NZE before the age of 13, and those in the late immersed group were immersed after the age of 15. A babble noise was played from eight azimuthal angles (0, ±45∘, ±90∘, ±135∘, 180∘) while the target speech, which was sentences from the Bamford–Kowal–Bench (BKB) corpus, was played from 0∘. Early immersed listeners were able to understand speech better than late immersed listeners within most of the room acoustics tested. However, once the room acoustics caused too adverse listening conditions at a high RT and low C50, neither group could benefit from SRM. The early immersed group was also able to make use of spatial cues to benefit from SRM more than the late immersed group, even in the least reverberant room scenario in the current study. Finally, while room acoustics affected how the groups benefitted from SRM, this effect was only observed when the source was located 5 m from the listener.