Geoscience Reference
In-Depth Information
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Sound pressure level
: Sound pressure level on a logarithmic scale in
Decibel (dB) serves as a common noise indicator. For example, the
END calculates A-weighted long-term average sound pressure levels
(EU 2002).
•
Frequency spectrum
: A sound source emits waves of different
frequencies measured in Hertz (Hz). With frequency on a logarithmic
scale the distribution of sound energy over frequency is defined as
frequency spectrum.
•
Spatial reach
: Soundscape surveys often map the spatial reach or extent
of an auditory perceived sound (Schafer 1977).
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Noise limit value
: There are regional, national, and international noise
limit values that are both recommendations and stipulations by law. For
example, the WHO observes sleep disturbances at noise levels above 40
dB (WHO 2009).
•
Rhythm
: Sound is a four-dimensional phenomenon and undergoes
spatio-temporal changes. Soundscape research considers this
characteristic by describing sound sources in terms of their rhythm
(Schafer 1977).
5- Visual Encoding
With the technique of visual encoding, we systematically assign graphic
variables to the previously defined acoustic parameters informed by
cartography and information design. We employ plausible codifications
according to established practice based on perceptual and cognitive
principles (MacEachren 1995, Bertin 1974, Cleveland and McGill 1984,
Mackinlay 1986). The objective of the encoding is to provide a unique and
discernible graphic counterpart for each parameter which matches its
physical characteristics and variability. In the case of correct encoding, the
graphic variables allow recognition, permit estimation, and exhibit
association with the underlying phenomena. It must be possible to utilize
and read the graphic variable alone as well as in combination with other
dependent variables. The aim is thus a systematic and modular usage of the
variables for reoccurring visualization needs within various domains.