The Effect of Underwater Acoustics on Whales
Whales utilize acoustic frequencies to communicate underwater. If the
whales are unable to communicate their bi-annual migration can become
perilous. Man-made low frequency sonarcan prevent whales from
producing soundand sometimes causes them to take alternate routes.
When the whales try to avoid the sonar they are in danger of running
ashore and perishing after being beached.
Twice a year, around the months of December and May, populations of
gray whales migrate from Mexico to Alaska. (Unknown1, 2002) During
this journey, they pass the state of California, where acoustical
pulses, generated by air guns or water guns, are used in seismic
surveys. If the seismic-generated sound waves exceed the "background"
noise or normal amount of noise, they could interfere with gray whale
communication or disturb behavior. (Unknown1, 2002) It is possible
that seismic surveys have a detrimental impact on marine life, such as
Whales are able to perceive sound in a wide range of frequencies from
75 Hz up to 150 Hz. In experimental conditions, where the
environment's level of noise is controlled, the whales are more
sensitive and hear from 10 Hz to 100 Hz. In addition, smaller whales
have a broader range from which they can hear from 10 up to 300Hz.
Whales depend on sound for communication, navigation, and even
detection of predators and prey. The seismic-generated sound waves may
disturb critical abilities. Disruption of any of their vital functions
can significantly disturb the fitness of whales. (Unknown3) There are
many factors that affect the communication abilities of the whales.
Temperature and pressure variations found at the varying depths of the
oceans can act as voice tubes and channel whale calls further than
usual, which allows for whales on the other side of the ocean to hear
the calls. It is in such a fashion that pods may keep in communication
with one another. Whales travel in pods. The pods can be compared to
schools of fish. Many other whales also use infrasound to communicate,
whether it is used as a method to attract mates, warn rivals,
communicate between the individuals of their own pods or of another
pod, or to find food. (Gerrow, E. 2002) Infrasound is wave phenomenon
sharing the physical nature of sound but with a range of frequencies
below that of human hearing. The marine acoustics affect the whales
such that the migration patterns are altered.
Marine acoustics are an extraordinarily technological matter. There is
no way to compare the noise levels in air and the noise levels in the
sea, because the standard reference pressures used underwater and air
are not the same. Measuring the decibels (dB) used to quantify
underwater sounds cannot be used to determine the...