Alexandra Brown

Urban noise surveys

Abstract Despite the large number of urban noise surveys which have been conducted to date, there are considerable weaknesses in the large body of data that such surveys have collected. For example, there are little data available which allow comparison of the acoustic environment of one city, or the noise exposure of its residents, with those of another. This is symptomatic of past approaches to urban noise surveys in which there has been misunderstanding of the nature of the urban acoustic environment to be measured and confusion resulting from multiple survey objectives. The major problem is that most survey results have been reported mainly as site-specific data. A review of 20 past survey procedures shows that the surveys can be categorized into four types: random sampling, sampling by land-use category, receptor-oriented sampling and source-oriented sampling. Various weaknesses in the different types are examined and it is suggested that several survey types and various survey objectives are incompatible. Receptor-oriented surveys would appear to offer the best opportunity for gathering noise level data which can be generalized from site-specific information to the exposure of a population. Disaggregation of noise by source type during a measurement programme could make the collection of noise data in urban noise surveys more efficient.

Levels of ambient noise in Hong Kong

Abstract Road traffic noise is nearly always the main contributor to long-term ambient noise levels in urban areas. Noise measurements conducted outside dwellings in Hong Kong show that the background levels ( L 90 ) from road traffic are high, with half of the study population exposed to levels some 20 dB above those measured in a UK study of the (whole) population of England. L 10 levels are also generally higher than for urban sub-populations in the USA and the UK, but not much different from those in London. The high levels, and the compressed range of the noise distribution, result from the absence, in a high-rise city, of space and of the shielding and ground effects which play a major role in attenuating road traffic noise levels in most urban areas. Despite the complex urban form, the noise level distribution, or L 90 by itself, can be predicted from basic information on geometry and traffic flow, but with an accuracy that can only be regarded as marginal for practical use. The receptor-oriented sampling approach in this study has produced information about the exposure of the population rather than the site-specific data commonly produced in urban noise surveys. Editing non-road-traffic sources from the measurements has enabled an efficient collection of data and ensured that the results could be replicated.

EXPOSURE OF THE AUSTRALIAN POPULATION TO ROAD TRAFFIC NOISE

Abstract This paper reports the results of a study to estimate the exposure of the Australian population to road traffic noise. A sample size of 264 dwellings, randomly selected throughout all Australian urban centres with a population of more than 100 000 people, was used in the study. Road traffic noise levels were predicted at each dwelling in the sample. The study estimated that over 9% of the Australian population are exposed to L A10, 18h values of 68 dB or above, and 19% to 63 dB or above. Confidence bands for these estimates are provided. The exposure estimate is compared to similar estimates in other OECD countries.

Perceptual constancy in auditory perception of distance to railway tracks

Distance to a sound source can be accurately estimated solely from auditory information. With a sound source such as a train that is passing by at a relatively large distance, the most important auditory information for the listener for estimating its distance consists of the intensity of the sound, spectral changes in the sound caused by air absorption, and the motion-induced rate of change of intensity. However, these cues are relative because prior information/experience of the sound source-its source power, its spectrum and the typical speed at which it moves-is required for such distance estimates. This paper describes two listening experiments that allow investigation of further prior contextual information taken into account by listeners-viz., whether they are indoors or outdoors. Asked to estimate the distance to the track of a railway, it is shown that listeners assessing sounds heard inside the dwelling based their distance estimates on the expected train passby sound level outdoors rather than on the passby sound level actually experienced indoors. This form of perceptual constancy may have consequences for the assessment of annoyance caused by railway noise.

Architectural Projects of Marco Frascari: The Pleasure of a Demonstration

Marco Frascari (1945–2013) was an Italian architect, theorist and academic who studied and taught at the Instituto Universitario di Architettura di Venizia (IUAV) under Carlo Scarpa, before moving to the United States in 1975. Over the course of his career, Frascari established himself as a highly respected educator. He was instrumental in the foundation and development of a number of PhD programmes across North America, including those at the University of Pennsylvania, the Washington Alexandria Architecture Center and the Azrieli School of Architecture and Urbanism in Ottawa