Auditory distraction by speech: Can a babble masker restore working memory performance and subjective perception to baseline?

Background speech has a detrimental impact on employees' privacy perception and cognitive performance in open-plan offices. Sound masking that covers speech sounds can help to improve the speech privacy and the ability to work undisturbed in open office environments. Recently, non-artificial sounds such as babble or water sounds have been suggested as masking sounds because they may be perceived as more natural and subsequently less annoying. This paper compares the working memory performance and annoyance perception during background speech that was masked by different babble sounds and a waterfall sound to speech that was masked by stationary noise with the frequency spectrum of the distracting background speech signal (target speech). In a first laboratory experiment the effects of different babble sounds were compared with the noise sound at a speech-to-noise ratio of−3 dB. All subjects had to complete a serial short-term memory task and a questionnaire that covered subjective ratings. All sound conditions with masked target speech produced similar error rates and annoyance ratings as unmasked target speech. In a second laboratory experiment, the speech-to-noise ratio of target speech that was masked by babble consisting of 48 target speech signals was varied between −6 and −12 dB in steps of 3 dB. Target based babble resulted in similar error rates as stationary noise at−6 dB speech- to-noise ratio but the findings suggest that target speech that is masked by babble might even be perceived as more annoying than speech that is masked by stationary target spectrum based noise.