Sonic Patterns I: The Noise - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 143

The active space for an equivalent signal is expected to be smaller in the urban
context than in nonurban areas, although a recent investigation (Mokford
et al. 2011 ) has found that urban habitat probably may degrade sound less than in
rural settings.
Anthropogenic sound interferes with these parameters, but also the structure of
urban spaces produces distortion in the sonic environment. For instance, large
vertical surface of buildings reflect sound and produce reverberation.
Investigation on the brown-headed cowbird ( Molothrus ater ) by Gall
et al. ( 2012 ) has proved that the active space of this species is affected by both
habitat type and level of urbanization. The maximum active space was obtained at
high frequency (4-6 kHz) and is larger in open urban spaces. The presence of
reflecting surfaces probably favors the propagation of sounds.

6.5 The Noise Context

Noise is part of any environmental context and concurs to characterize a site assigning
a well-being score or an economic value (see for instance, O'Connor 2008 ). According
to its origin and level, noise can have a different impact on living organisms.
The substrate on which noise is produced can modify physical and perceptual
noise. For instance, noise produced by the wind flowing in broadleaved trees is
different from the noise produced by coniferous crowns.
Ambient noise is produced by a broad spectrum of different spectral frequencies.
A large variety of frequencies is produced by wind passing through leaves (rustling)
and twigs. Wind passing over substrates generally produces low-frequency sounds.
Anthropogenic noises pertain to a wide spectrum of frequencies, but the
anthrophonies that are real intruders at a growing rate in every environment are
generally of low frequency. The spectral profile of every environment is peculiar
for that ambient or, better, is habitat specific. It reflects geography, topography,
botanical composition, and vegetational structure (clearings, core/edge areas, shape
of patches, fragmentation level and typology, land use, level of human contamina-
tion, etc.).
In a nontechnological world, sounds are the manifestation of geophysical and
biophysical dynamics. Thunder, wind, running water, and rain are common sounds
from nature. But animals too contribute to such sounds, that Bernie Krause has
called the “Great Animal Orchestra” (Krause 2012 ). In the modern world
dominated by humans, the word “sound” is often neglected and substituted by the
word “noise,” that is defined as every sonic process far from quiet that is annoying
and may be harmful.
When too loud ( 100 dB), noise can produce temporary or permanent damage

to the hearing system in humans and animals as well. Modern music when heard at
the highest volume can create permanent deafness in youths. Noise is responsible
for the so-called noise pollution, and mitigation or remediation actions are at the

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