Effect of room acoustic properties and head orientation on practical speech-in-noise measurements for various spatial configurations

Speech recognition scores in noise can be affected by measurement conditions such as the spatial configuration, room acoustic properties, or the position and head orientation of a test person. This is critical when comparing repeated measurements, e.g., during hearing aid verification. While the basic effects of these factors are known, specific effect sizes for practically relevant configurations have not previously been reported. We investigated the effects of audiological test-room acoustics with low reverberation, and of head movements on speech-in-noise tests for typical spatial configurations. Speech-recognition thresholds (SRTs) and head movements were measured in 240 normal-hearing participants in six rooms for five loudspeaker configurations (S0N0, S0N±45, S0N±90, S0N180 and S±45N∓45). Additionally, head positions were reproduced with an artificial head, and using a binaural speech intelligibility model, binaural room impulse responses were measured to estimate the influence of head movements on the SRT. The results show that the effects of room acoustic properties and head movements varies greatly between spatial configurations. Head rotations around the vertical axis can affect speech recognition scores by up to 8 dB, most critically for the configuration S0N180. For spatially separated sound sources, different room acoustic conditions caused differences in SRT of up to 5 dB.