Audio-visual preferences, perception, and use of water features in open-plan offices.

This paper examines the use of water features for masking irrelevant speech and improving the soundscape of open-plan offices. Two laboratory experiments were carried out, as well as acoustic simulations and field tests. Experiment 1 aimed to identify the preferred sound level of water sounds against irrelevant speech. Experiment 2 examined the audio-only and audio-visual preferences and perception of waterscapes. Acoustic simulations and field tests examined the impact of design factors. The results showed that, when played against a constant level of irrelevant speech of 48 dBA, people prefer to listen to water sounds of 42-48 dBA (45 dBA being best). These results and results from previous research suggest that water sounds work mainly as informational maskers rather than energetic maskers. Furthermore, the introduction of a water feature improved the perception of the sound environment, and adding visual stimuli improved perception by up to 2.5 times. Acoustic simulations indicated that features at each corner and one at the center (or a single feature with an array of speakers) can provide appropriate masking for a large open-plan office, whilst field tests showed that water sounds decrease the distraction and privacy distances significantly (clusters of workstations benefitting more than rows of workstations).

Audio-visual interaction and perceptual assessment of water features used over road traffic noise.

This paper examines the audio-visual interaction and perception of water features used over road traffic noise, including their semantic aural properties, as well as their categorization and evocation properties. The research focused on a wide range of small to medium sized water features that can be used in gardens and parks to promote peacefulness and relaxation. Paired comparisons highlighted the inter-dependence between uni-modal (audio-only or visual-only) and bi-modal (audio-visual) perception, indicating that equal attention should be given to the design of both stimuli. In general, natural looking features tended to increase preference scores (compared to audio-only paired comparison scores), while manmade looking features decreased them. Semantic descriptors showed significant correlations with preferences and were found to be more reliable design criteria than physical parameters. A principal component analysis identified three components within the nine semantic attributes tested: "emotional assessment," "sound quality," and "envelopment and temporal variation." The first two showed significant correlations with audio-only preferences, "emotional assessment" being the most important predictor of preferences, and its attributes naturalness, relaxation, and freshness also being significantly correlated with preferences. Categorization results indicated that natural stream sounds are easily identifiable (unlike waterfalls and fountains), while evocation results showed no unique relationship with preferences.

Acoustical and perceptual assessment of water sounds and their use over road traffic noise.

This paper examines physical and perceptual properties of water sounds generated by small to medium sized water features that have applications for road traffic noise masking. A large variety of water sounds were produced in the laboratory by varying design parameters. Analysis showed that estimations can be made on how these parameters affect sound pressure levels, frequency content, and psychoacoustic properties. Comparisons with road traffic noise showed that there is a mismatch between the frequency responses of traffic noise and water sounds, with the exception of waterfalls with high flow rates, which can generate large low frequency levels comparable to traffic noise. Perceptual assessments were carried out in the context of peacefulness and relaxation, where both water sounds and noise from dense road traffic were audible. Results showed that water sounds should be similar or not less than 3 dB below the road traffic noise level (confirming previous research), and that stream sounds tend to be preferred to fountain sounds, which are in turn preferred to waterfall sounds. Analysis made on groups of sounds also indicated that low sharpness and large temporal variations were preferred on average, although no acoustical or psychoacoustical parameter correlated well with the individual sound preferences.