Binaural Unmasking in Practical Use: Perceived Level of Phase-inverted Speech in Environmental Noise

TL;DR

The paper tackles the challenge of making target sounds in noisy environments more audible without increasing overall loudness or eliminating ambient sounds. It proposes BHLD as a practical metric to quantify audibility gains from interaural phase differences, operationalized through phase reversal in one ear. The study systematically evaluates multiple speech signals and everyday noises under realistic listening conditions, showing consistent BHLD improvements around 5–6 dB across conditions, with variations tied to frequency-band inversion and signal/noise spectra. The findings suggest a feasible engineering route for binaural unmasking in earphones, balancing audible gain with user comfort and safety, and highlighting potential for safer listening at reduced SPLs.

Abstract

We aim to develop a technology that makes the sound from earphones and headphones easier to hear without increasing the sound pressure or eliminating ambient noise. To this end, we focus on harnessing the phenomenon of binaural unmasking through phase reversal in one ear. Specifically, we conduct experiments to evaluate the improvement of audibility caused by the phenomenon, using conditions that approximate practical scenarios. We use speech sounds by various speakers and noises that can be encountered in daily life (urban environmental sounds, cheers) to verify the effects of binaural unmasking under conditions close to practical situations. The results of experiments using the Japanese language showed that (i) speech in a noisy environment is perceived to be up to about 6 dB louder with phase reversal in one ear, and (ii) a certain effect (improvement of audibility by 5 dB or more) is obtained for all speakers and noises targeted in this study. These findings demonstrate the effectiveness of binaural unmasking attributed to interaural phase differences in practical scenarios.

Figures (14)

• Figure 1: Schematic diagram of BHLD.
• Figure 2: Procedure of the experiment.
• Figure 3: User interface for the experiment.
• Figure 4: Layout of equipment.
• Figure 5: Block diagram of signal processing in PC.