Speech intelligibility in noise with varying spatial acoustics under Ambisonics-based sound reproduction system

The present study investigates the effect of noise on speech intelligibility under an Ambisonics-based sound reproduction system, which is a commonly used technique for realising audio virtual reality. The sound reproduction system was built in an anechoic chamber using a 16 channel spherical loudspeaker array. A commercially available first-order Ambisonics microphone array was utilised for collecting room impulse responses of rooms with different acoustic characteristics, and a decoder for generating signals rendered from the loudspeaker array. A subjective listening test was conducted in the sound reproduction system examining how intelligibility of sentences is compromised by noise under virtually reproduced acoustics environments with various acoustical conditions. Particular focus was given to investigating the effect of the amount of reverberation in rooms as well as the angular separation between the target speech and noise sources, both of which are known to have a significant effect on speech intelligibility in real (i.e. non-virtual) acoustic environment. The experimental results suggest that the intelligibility of speech masked by pink noise was significantly reduced under reverberant acoustical environments reproduced by the Ambisonics-based sound reproduction system compared to the baseline anechoic environment. However, only marginal differences were observed between the acoustical environments with different reverberation time. The effect of spatial release from masking was also observed under the reproduced acoustic environments and showed some correlation with the accuracy of source localisation realised by the sound reproduction system.