Research into the practical and policy applications of soundscape concepts and techniques in urban areas (NANR 200)

Executive Summary 1 The aim of this review was to investigate existing research into soundscape concepts and to produce recommendations for future research into the practical identification, management and enhancement of soundscapes in urban areas. 2 Existing research on soundscapes was investigated using four methods: i. a survey of more than 500 papers in the academic literature, ii. an analysis of 27 case studies of soundscape assessment, iii. an analysis of 15 case studies of soundscape design, and iv. interviews with five key soundscape experts. Analysis of this data was conducted to identify significant gaps in the knowledge base and suggest a way of obtaining a practical soundscape assessment method. 3 Soundscapes were found to be a highly multi-disciplinary topic, with many different ideas, concepts, aims and methods evident in the literature. The definition of the term soundscape is itself not settled; for the purposes of this project, we have defined it as “the totality of all sounds within a location with an emphasis on the relationship between individual’s or society’s perception of, understanding of and interaction with the sonic environment. ” 4 This review highlights that a range of methodological approaches have been used to establish classifications and categorisations of sounds and soundscapes. The relationship between different categories of sounds and their interaction needs to be considered to increase the understanding of soundscape assessments and to derive soundscape classifications. 5 The different methods and tools used to assess soundscapes, in a variety of locations, each have advantages and disadvantages; using a number of methods in one case study can help to mitigate against the disadvantages of any one method. The case studies assessed in this report demonstrate the importance of individual and demographic similarities/differences, people’s behaviour, physical aspects of the soundscape, other sensory and environmental elements, and the general location and context, in understanding and assessing soundscapes. 6 Soundscape assessments involving a subjective component have highlighted a number of variables that play a part in the assessment. These include the individual’s knowledge and prior experience of the soundscape, the meaning they derive from it, their attitude towards the sound source, their behaviour, their noise sensitivity, demographic and cultural dimensions, and their sense of control over the noise. 7 Research has shown that sometimes a soundscape is perceived as a collection of the individual sounds of which it is comprised; soundscape assessments are therefore related to the assessment of those sound types. This implies that soundscape assessment relies upon the identification of the sounds, the prominence of the sounds, and potentially the ratio of certain sound types to other sound types within the soundscape. It is also highlighted that, because the soundscape varies over time, note must be taken of the fact that any soundscape assessment relates to a singular moment in time. Furthermore, research has shown that soundscape assessments can be dependent on an individual’s memory (when using subjective assessments methods) and/or the segment of the soundscape that was recorded (when playing back recorded soundscapes in a laboratory situation). 8 Multi-sensory experience is also shown to be highly relevant to soundscape assessment and must therefore be acknowledged as soundscapes are not perceived in sensory isolation; in particular audio-visual interactions have been shown to have an effect on soundscape perception. Many researchers point to the importance of understanding the full environmental and social context for soundscape assessment, the relevance of comparing similar place types, and the effect of moving between one soundscape and another on an assessment. 9 Turning to the subject of soundscape design, it is noted that there is a dearth of case studies involving the modification and design of soundscapes, both in the UK and internationally. The rationale behind many of the case studies’ focus upon or consideration of sound was the improvement of a soundscape that was negatively affected by the sound of traffic. Approaches to soundscape design varied, ranging from the use of noise control elements, such as barriers and absorbers, to the utilisation or exploitation of natural elements that already exist in the location. Some case studies introduced sounds to the soundscape, in particular water sounds, while others incorporated specific sonic art installations to alter the soundscape or detract attention from existing features of the soundscape. A number of case studies used design alterations to improve the soundscape and perception of the soundscape including altering visual aspects of the place, altering the layout of the area, pedestrianisation of the area, and providing entertainment facilities (e.g. cafes). 10 Case studies whereby design modifications or interventions have taken place, have had little or no formal evaluation of their success. The studies that were evaluated used a number of different methods involving both objective and subjective measures and included the experimental comparison of subjective ratings, observations of people’s behaviour, recognition and awards for good designs, and level of complaints about the soundscape. This demonstrates that different evaluation tools may be necessary dependent upon the type of soundscape intervention being evaluated. Additionally, by combining methods to produce an interdisciplinary evaluation, a more accurate understanding of the success of the soundscape design is possible, hence improving future interventions. 11 The relationship between environment and individual is complex, with many factors, some of which cannot currently be quantified. Important factors include: prominent individual sound sources, the interaction of sources, other sensory stimuli and contextual and individual factors such as meaning, and expectation. Some of these factors can be captured by subjective rating scales for high-level concepts like ‘calmness’, ‘vibrancy’ and ‘spaciousness’. Other factors, such as the semantic meaning of a soundscape are best characterised currently by qualitative descriptors. There are good prospects for developing objective acoustic metrics to evaluate some factors but in most cases this work is still at an early stage, and the methods developed so far have only been applied in specific contexts; to provide metrics that are more broadly applicable they would need to be evaluated in a broader range of locations and conditions. The expert interviews and case studies illustrated the diversity of views across different disciplines on the most promising soundscape methods. All the interviewees agreed on the need for an interdisciplinary approach, and on the need to retain some form of subjective rating when assessing soundscapes. 12 Ultimately, six important gaps have been identified in the soundscape knowledge base. These are areas where more research would significantly improve understanding soundscape assessments. These gaps have been identified as: i. a lack of genuinely interdisciplinary projects (characterised by a shared perspective) instead of multidisciplinary projects (where researchers work in parallel within their own disciplines). These are needed to deal with the multidimensional experience of soundscape perception. ii. a lack of basic knowledge on many aspects of soundscape cognition, perception and classification. iii.a need for large-scale robust field trials of soundscape assessment methods instead of the more common experiment of a new method in a single location. iv. a need to develop more soundscape-specific indicators and tools that could eventually be used for soundscape design. v. a need to rigorously assess deliberate soundscape interventions to understand which design aspects work and which do not. vi. a lack of a close connection between soundscape research, design and planning practice. 13 Finally, a new research project is proposed to develop a robust field assessment method. The aim of this project is to develop a method based on existing research methods but introducing greater confidence by trialling the method across many real urban soundscapes. Options are presented for developing a purely qualitative assessment tool or one that incorporates and integrates both qualitative and quantitative ratings. 14 We recommend that a first step for an assessment method, which could realistically be developed in the near future, should be based on qualitative methods. A second iteration of this soundscape assessment tool could supplement the qualitative techniques with quantitative methods, first based on subjective rating scales and eventually on objective metrics which predict the subjective ratings.