The effect of spatial separation of sound masking and distracting speech sounds on working memory performance and annoyance

The application of sound masking in office environments aims at reducing the disturbing impact of background speech. When a masker and speech signal are presented from different directions, spatial release from masking occurs that results in lower speech privacy. This paper analyzed the resulting effect of spatial separation on working memory performance and subjective annoyance. Existing prediction models for the cognitive performance were applied to binaural sound conditions. Binaural audio files were recorded in an anechoic chamber and open-plan office and played to subjects through headphones in a laboratory experiment. When the distracting speech signal was presented from the left side and a noise signal from behind at a speech-to-noise ratio of −9 dB in the free field as opposed to a presentation of speech and noise signals from behind, the mean error rate and annoyance perception increased. Spatial separation of the speech and noise sources by moving the masker to the left showed in the open-plan office an effect on working memory performance at a speech-to-noise ratio of −9 dB. The findings indicate that spatial separation might only have a small disadvantageous effect on cognitive performance and annoyance perception. Further analysis showed that the serial recall performance correlates with the better-ear Speech Transmission Index.