research | acoustics.06

Soundscape. A soundscape is a sound or combination of sounds that forms or arises from an immersive environment. The study of soundscape is the subject of acoustic ecology. The idea of soundscape refers to both the natural acoustic environment, consisting of natural sounds, including animal vocalizations and, for instance, the sounds of weather and other natural elements; and environmental sounds created by humans, through musical composition, sound design, and other ordinary human activities including conversation, work, and sounds of mechanical origin resulting from use of industrial technology. The disruption of these acoustic environments results in noise pollution.
The term “soundscape” can also refer to an audio recording or performance of sounds that create the sensation of experiencing a particular acoustic environment, or compositions created using the “found sounds” of an acoustic environment, either exclusively or in conjunction with musical performances.

The term soundscape was coined by Canadian composer and environmentalist, R. Murray Schafer. According to this author there are three main elements of the soundscape:
Keynote sounds
This is a musical term that identifies the key of a piece, not always audible… the key might stray from the original, but it will return. The keynote sounds may not always be heard consciously, but they “outline the character of the people living there” (Schafer). They are created by nature (geography and climate): wind, water, forests, plains, birds, insects, animals. In many urban areas, traffic has become the keynote sound.
Sound signals
These are foreground sounds, which are listened to consciously; examples would be warning devices, bells, whistles, horns, sirens, etc.
Soundmark
This is derived from the term landmark. A soundmark is a sound which is unique to an area.
Papers on noise pollution are increasingly taking a holistic, soundscape approach to noise control. Whereas acoustics tends to rely on lab measurements and individual acoustic characteristics of cars and so on, soundscape takes a top-down approach. Drawing on John Cage’s ideas of the whole world as composition, soundscape researchers investigate people’s attitudes to soundscapes as a whole rather than individual aspects – and look at how the entire environment can be changed to be more pleasing to the ear.
It has been suggested that people’s opportunity to access quiet, natural places in urban areas can be enhanced by improving the ecological quality of urban green spaces through targeted planning and design and that in turn has psychological benefits.

Acoustic Ecology. Acoustic ecology, sometimes called soundscape ecology, is the relationship, mediated through sound, between living beings and their environment. Acoustic ecology is a discipline that analyzes how we interpret, and are affected by natural and artificial sounds around us.

Noise Map. A noise map is a graphic representation of the sound level distribution existing in a given region, for a defined period. The main noise indicators for noise mapping are Lday, Levening, Lnight and Lden (day-evening-night). These are long-term averaged sound levels, determined over all the correspondent periods of a year. All of these indicators are defined in terms of A-weighted decibels (dBA, dB(A)). According to the END, the acoustic indicators can be determined by computation or measurement methods. But computation methods are widely preferred, because of the large amount of yearly averaged locations required. Using either approach, a grid of receivers must be defined in order to measure or calculate noise levels. When results are obtained, using GIS tools, spatial interpolation must be applied in order to give a continuous graphical representation of sound levels. Five dBA ranges are used for this contour (isoline) representation. The maps may be useful for planning stages, or for prior evaluation of action plans, determination of most polluted areas. A strategic noise map, furthermore, must make an evaluation of the amount of people exposed within the five dBA ranges. Facade sound levels must be calculated, or estimated from the previous map. here are several models for making noise maps. Some of them use empirical models (for instance, INM for airports noise mapping), but most of the models are based in the physics of propagation of sound outdoors (defined in ISO 9613). The use of these software packages is quite easy, and the accuracy of results is very high depending on the quality of input data to the models. Measurements are used very often for the validation of results.
For train and road traffic noise, the description of the sources is usually made in terms of easy to know parameters, such as speed, number of vehicles etc. The main challenge for the acoustic consultant is the creation of good digital terrain model (DTM).
For industrial noise map production, the most important thing is the description of noise sources: sound power levels, directivity, working periods. Although some databases can be found, in many cases it is necessary to make measurements (ISO 3740) for describing the source. When these data are known, it will be necessary to simulate each of sources using a combination of point, line or surface noise source. The creation of good acoustic models can be quite complicated, and only experienced consultants can front this difficult tasks.
Some of the software packages more used for noise mapping are: LimA, CadnA, IMMI, Predictor, and SoundPlan. These programs have been adapted to fulfil the strategic noise mapping requirements of the END.
Simulation tools are very useful specially at planning stages, where measurements are not possible. The consultant can evaluate the effectiveness of action plans, in order to take decisions.

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