Research Plans for Improving Understanding of Effects of Very Low-Frequency Noise of Heavy Lift Rotorcraft

This report reviews the English-language technical literature on infrasonic and low-frequency noise effects; identifies the most salient effects of noise produced by a future large civil tiltrotor aircraft on crew, passengers, and communities near landing areas; and recommends research needed to improve understanding of the effects of such noise on passengers, crew, and residents of areas near landing pads

Acoustics of Sequential Spaces

“Sequential spaces” are spatial systems comprising multiple spaces in sequence connected by openings, common in public spaces with crowd transit (e.g., museums, shopping malls, and transportation hubs). Related to sound diffraction and insulation, this thesis aims to achieve a minor breakthrough in architectural acoustics through establishing disciplines, not focusing on a single or performance space, but targeting large-scale buildings with a listener in motion. The necessity of applying good practice in asymmetric dynamic auditory perception between approaching and receding sound sources, and inconsistent sound attenuation with distance for separating partitions of same construction is demonstrated by subjective and objective outcomes through real and virtual acoustics. The first stage observes dynamic auditory perception of noise as a stationary primary sound source in a museum. The asymmetry of the loudness and listener envelopment between approaching and receding sources occurs with broadband noise. Perceptual priority increases with a rising level. The second stage confirms sound attenuation with distance in accordance with the needs of users (connected room volume, individual room volume, source position, and room absorption) in practice. As connected room volume increases, average sound pressure level is remained for rooms originally connected, while reverberation time generally decreases. The level difference between source and first receiving room is magnified to 1.5 times the sequential one. The third stage explores sound attenuation with distance when parameters of contextual (opening dimension and position, number of rooms), acoustic (absorption coefficient and distribution) and source (directional radiation from the opening and an additional source) factors are efficient in predictions based on finite element method. The final stage examines dynamic auditory perception of voice and music with or without background noise through a validated reproduction of virtual environment. Three perceptual distinctions emerge between approaching or receding sound sources and are defined as approach, plummet, and convergence effect

Soundscape design of water features used in outdoor spaces where road traffic noise is audible

This research focused on the soundscape design of a wide range of small to medium sized water features (waterfalls, fountains with upward jet(s), and streams) which can be used in gardens or parks for promoting peacefulness and relaxation in the presence of road traffic noise. Firstly, the thesis examined the audio-visual interaction and perceptual assessment of water features, including the semantic components and the qualitative categorisation and evocation of water sounds; and secondly, the thesis investigated the effectiveness of the water features tested in promoting relaxation through sound mapping. Different laboratory tests were carried out, and these included paired comparison tests (audio-only, visual-only and audio-visual tests), semantic differential tests, as well as tests aimed at the qualitative categorisation and evocation of water features. Sound maps of the water generated sounds were developed through the use of propagation models based on either point or line sources. Three acoustic zones (‘water sounds dominant zone’, ‘optimum zone’ and ‘RTN dominant zone’ (RTN: road traffic noise)) were defined in the maps as the zones where relaxation/pleasantness can be promoted over a 20 m × 20 m area for different road traffic noise levels. Paired comparisons highlighted the interdependence 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. Categorisation results indicated that natural stream sounds are easily identifiable (unlike waterfalls and fountains), while evocation results showed no unique relationship with preferences. The results of sound maps indicated that small to medium sized water features can be used mainly in environments where road traffic noise levels are equal or lower than 65 dBA

A study to explore smellscape: from understanding and interpretation to evaluation and design in urban intermodal transit spaces in UK and China

This study aims to generate a systematic approach to exploring smellscape, from understanding and interpretation to evaluation and design in a specific type of public space - urban intermodal transit spaces, that large numbers of people visit every day, and which have intensive traffic flows and various functions. Taken Grounded Theory as a methodological approach, this study took one typical case from each country, Wuchang Railway Transit Centre and Sheffield Railway Station and Bus Interchange, to explore smellscapes in intermodal transit spaces in China and UK. An analytic procedure has been generated from the studied cases explaining people’s perception of smell environments through key elements in the concept, influenced by eleven perceptual patterns. This analysis answers the question of how to understand and interpret smellscape. In terms of people’s assessment of the pleasantness of smellscape, nine indicators were identified, which have been developed into a framework for measuring smellscape quality and classifying different types of smellscapes. The most dominant type of pleasantness in urban intermodal transit spaces is mainly influenced by cleanness and freshness. The perceptual process and evaluation criteria help with understanding and analysing existing smellscapes, and also inform the design objective for achieving a pleasant smellscape in target spaces. In terms of designing a pleasant smellscape in the target context, a design framework has been constructed at three scales with design methods and examples, responding to identified components from smells and smell sources, individual differences, physical environmental settings and contextual issues. This also gives an example of integrating smellscape design into a traditional design framework for a specified functional public space at the macro, midi and micro levels