Page 10 - January 2007

ASA meeting in Vancouver, Canada on May 16, 2005. Areas identified for further development at this workshop included: economics/noise policy-standards, combined effects, common protocols/cross cultural studies and edu- cation about soundscape. Other areas identified include: improve combined measurement procedures: qualitative and quantitative parameters—including the character of sounds and cross-cultural questionnaires. The importance of survey site selection was emphasized. The combined soundscape approach requires that physical noise criteria match qualitative descriptors. There is a need to correlate complaint language with metrics for policy, and to intro- duce the qualitative methods of psychology and sociology to engineering analysis, combining quantitative and qual- itative tools for land use planning. Soundscape analysis should place sound in context, with noise and sound linked to activity at realistic study sites. We must distin- guish the totality of soundscape from the limited idea of a quiet zone. The connection between research and design for communities is a creative process. To complete this connection we need methods to: measure and identify design values, develop a lexicon of qualities/values for soundscape design, investigate a subject’s control/non- control over the environment, understand the motivation of people to choose a particular environment, and create soundscape simulations of proposed sites for evaluation by officials and the public. Continuing soundscape research should provide practical data that can be applied by designers to create pleasing acoustical environments.
This article describes a range of measures and solu- tions needed to identify an integrated model to design/improve soundscapes and enhance urban planning concepts. Of course, we are aware that these are early steps
2
and scientific and applied work is still to be done. Community noise assessment is an increasingly important means by which to improve the quality of mod- ern life, particularly in urban outdoor settings. The effects that community noise has on residents, businesses and other stakeholders must be assessed accurately to create the political and cultural climate needed to positively affect the environmental soundscapes. This climate includes an effective policy structure which recognizes the impacts of sound on the community, planning, and design principles which can be applied to specific projects and
settings.
Soundscape analysis combines the physical measure-
ment of sound with a scientific investigation and evalua- tion of the community perception of sound. The methods of soundscape analysis can provide the practical tools for achieving beneficial results in outdoor sound quality through the application of thoughtful community noise
3–6
Combining physical, psychoacoustical, and perceptu- al measurements
In the context of community noise, there is a common consent about the necessity of additional parameters beside the A-weighted sound pressure level (SPL). The A-weight- ed and energy-equivalent Intensity Level (IL) and loudness
policy, environmental planning, and design.
measurements are not sufficient for understanding human perception or for adequate description of an urban sound- scape. Essentially, the introduction of new parameters, the more sophisticated use of existing parameters, and a merged approach from different measurement procedures appear to be inevitable.
Physical and psychoacoustical measurements
The physical measurement of relevant acoustical parameters in an outdoor setting is a requisite first step in evaluating that environment. These methods of measure- ment and analysis are becoming increasingly sophisticated. They range from the simple measurement of overall A- weighted level samples, time histories, statistical and spec- tral analyses, through the compilation of time-variant Zwicker loudness tableaus and further psychoacoustic evaluation and analysis.
Therefore, psychoacoustic parameters should be applied to measure and assess environmental sound more properly. With the help of psychoacoustic parameters that are mainly based on standardized procedures of measure- ment and analysis, it may be possible to explain why some environmental sound sources are more annoying—or pleasing—than others.
Relating human hearing and objective measurement
Human hearing differs in many fascinating (and sometimes frustrating) ways from conventional acoustic measurement devices and processes. It is spatially- and pattern-sensitive, easily detecting small changes in its sonic “surroundings” in any combination of level, location (including movement), time or frequency. A physically small source in a context of sounds coming from many directions can dominate attention by fluctuating and/or moving, even though its power contribution is a small
7
fraction of the whole. Consider the visual analogy of driv-
ing at dusk and distinctly noting the flashing LED taillight of a bicycle in the moderate distance—a pattern drawing your attention—and its significance (a “human weight- ing”). Were the light not flashing, the chances are that you would not have noticed it until getting much closer. Even in low dusk, its energy contribution to the scene is tiny, yet it is readily recognized. Such fluent and situation-depend- ent signal processing and weighting by the “human meas- uring system” challenges the selection of appropriate tech- nical methods to quantify sound situations and their objective significance in soundscapes.
Some options for matching measurements with per- ceptions include levels and spectra versus time, rather than overall A-weighted Leq, which are valuable in soundscape measurement. Note, Leq is not representative of the subjec- tive impression and contextual evaluation.
Psychoacoustic measures versus time—loudness, sharpness (essentially the ratio of high-frequency loudness to overall loudness), roughness (quick fluctuation), fluctu- ation strength (slow fluctuation) and others, overall and versus frequency, generally represent subjective auditory evaluations better than conventional level-based measure- ments.
8 Acoustics Today, January 2007