Laurent Galbrun

Noise levels and noise sources in acute care hospital wards

Noise in hospital wards has the potential to slow down the recovery of patients. A comprehensive and systematic analysis of noise levels and noise sources has been carried out in two intensive care units and one high dependency unit in two Edinburgh hospitals (UK). Noise levels LAeq,1min and LAFmax were measured at 1 minute intervals for 24 hour periods, and noise sources responsible for LAFmax were identified. High noise levels were found in the three wards, the lowest LAeq,1min being measured in the modern ward tested, where an acoustic ceiling was present. A substantial number of noise sources have been observed and analysed statistically, many of which had never been identified by previous research. It was found that 34% of these are totally avoidable and 28% are partially avoidable. Noise control solutions are presented, with practical solutions affecting 48% of the noise sources, and staff education affecting 14% of the sources. Practical application: The analysis and classification of noise sources obtained has lead to the identification and presentation of practical noise control solutions, some of which can be implemented at the design stage. This is of direct relevance to building services engineers who play a role in the design of hospital wards, and can therefore use this information. It can also be noted that average and maximum noise levels measured in this study could form the basis for the development of noise guidelines in intensive care units and high dependency units, as current limits do not appear to be appropriate for such spaces.

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.

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.

The modelling of vibration transmission through plate/beam structures typical of lightweight buildings

Vibration transmission through plate/beam structures typical of lightweight buildings is examined in this paper. Modelling difficulties are analysed and related to the several modelling choices available, including connection type, beam modelling, modal properties and material properties. A number of key experiments carried out on structures made of one or more parallel plates attached to a single beam are discussed, and the applicability and limitations of fundamental theories are identified through the use of Statistical Energy Analysis (SEA) models. It is shown that the interrelation between the various modelling factors can lead to complex models. The systems for which existing models can be used are identified, as well as those for which more complex models need to be developed.