Biology Reference
In-Depth Information
Future research should better represent groups of animals such as amphibians,
invertebrates, and reptiles that are not sufficiently studied. A comparative analysis
of the behavior of species exposed to equivalent noise pressure could allow us to
understand the different effects of noise and to suggest strategic procedures of
mitigation and of conservation management. Extension of the investigations to
infrasonic and ultrasonic frequencies can be extremely useful for better understand-
ing the adaptations of species that are really specialized in acoustic communication
not audible by humans. Finally, it remains of central importance to understand the
effects of accumulated noise in the short- and long term in populations and
communities.
Summary
Acoustic noise is a diffuse phenomenon in nature and especially in human-modified
ecosystems. Noise can be defined a sound with poor information or simply an
unwanted sound that can mask other sounds. The source noise may be of natural
(geophonies, biophonies) or manmade (anthrophonies) origin. The noise produced
by human activities has grown quite rapidly in the past century, covering the larger
part of the Earth. In particular, transportation facilities and logistics are the major
sources of noise (pollution). Noise reduces the distance from the sender at which a
signal can be detected by a receiver: this distance is called active space and
represents an important parameter in communication. Noise is a common word in
modern life and has been substituted for the generic term sound. Such substitution is
largely because of the scant interest that human society has reserved for the sonic
context. The patchy distribution of the sonic environment creates sonotopes with
variable noise conditions, which determines the final distribution of vocal species
according to their level of tolerance and adaptive plasticity.
Noise pollution may have long-term effects on populations and communities,
reshaping communities according to the level of noise tolerance between prey and
predators. Several effects of noise on vocal animals include direct stress, masking
predatory menace, and interference with the communication mechanisms in
general.
There is evidence that vocal animals try to reduce the effect of background noise
of either natural origin or anthropogenic origin, adopting at least two distinct
strategies: increasing the amplitude of the acoustic signals (Lombard effect) or
shifting the signal frequency.
The underwater environment is noisy: the sonic sources are in large part of
natural origin (wind, tides, rain, current turbulences). There is evidence that marine
systems can be distinguished according a specific sonic signature that results from
the combination of disparate sonic sources of natural and anthropogenic nature. The
increase of ocean acidification can produce an increase of noise diffusion caused by
the inverse correlation between water pH and sound transmission.
The sonic signature of marine systems can be documented also in freshwater
systems, and the effects of different sonic freshwater environments can be proven in
different species of fishes according to their level of hearing sensitivity.
Search WWH ::
Custom Search