Download A BBVA Foundation research project comes up with the first portable

PRESS OFFICE
PRESS RELEASE
The device was designed and built in the Laboratory of Applied
Bioacoustics at UPC (Universitat Politècnica de Catalunya), under the
direction of Michel André
A BBVA Foundation research project comes up
with the first portable system enabling in situ
detection of cetacean hearing loss

Obtaining accurate measurements of the hearing sensitivity of
cetaceans means assessments can be run on the survival chances of
stranded individuals after release to the wild, and will allow us to
calibrate their tolerance threshold versus noise pollution sources

Researchers have developed analysis models for the sound signal
sequences sperm whales emit while foraging for their prey – a process
known as biosonar – which conclude that this marine mammal is
capable of detecting a 25 cm squid at a distance of 2 kilometers

As a recent and largely unregulated phenomenon, man-made noise has
become one of the gravest threats facing the marine environment
December 17, 2008. A research project supported by the BBVA Foundation
and led by Michel André, director of the Laboratory of Applied Bioacoustics at
the UPC (Universitat Politècnica de Catalunya) has developed the world’s
first portable system for measuring cetacean hearing sensitivity.
This audiogram measurement system facilitates in situ diagnosis of
cetacean hearing loss, allowing assessments to be run on the survival
chances of stranded animals without having to transport them to a
laboratory. Researchers in Spain, the United Kingdom, France, the
Netherlands and the United States have taken part in this BBVA Foundation
project.
Cetaceans rank among the world’s most imperiled species, due, among other
reasons, to the noise produced by artificial sound sources. A number of
problems have recently come to light which bear a direct relation to sound
sources of human origin; among them, the growing number of cetacean deaths
in collisions with boats, or the mass beaching of whales after military
maneuvers. Oil and gas extraction too have added their share of noise pollution
to the marine environment.
To date, the only way to measure cetaceans’ hearing sensitivity was to remove
them to a laboratory. However this complex process entailed serious risks for
their survival, given their large size and the delicate state of health of stranded
individuals.
Among the innovative features of the new portable system developed
by Michel André’s team with the aid of the BBVA Foundation are its
electrical autonomy, measurement speed – just a few minutes suffice
to detect any auditory lesions – and its ability to generate stimuli from 10
Hz up to 200 kHz, encompassing the entire human hearing range (20 Hz- 20
kHz) and, naturally, that of cetaceans.
This novel system can ascertain how the animals’ brains react to sound signals,
as well as measuring cetaceans’ hearing sensitivity to certain frequencies by
analyzing the evoked potentials registered through the top of the skull. When
an animal hears a sound, its brain registers this vibration through an electrical
impulse that can be detected with simple suction cup electrodes. These
electrical pulses are called auditory evoked potentials or auditory brainstem
responses (ABR), and incorporate a short latency time and duration. In the case
of a rehabilitating stranded cetacean, this hearing analysis is vital in order to
determine whether it can correctly use its biosonar system and thus evaluate
its survival chances on release.
ELUCIDATING THE SPERM WHALE SONAR AND ITS DETECTION POWERS
Cetacean hearing systems are characterized by a series of unique
morphological adaptations allowing them to pick up frequencies that their
auditory channels translate into accurate acoustic images. At the same time, by
measuring the ear’s sensitivity to certain frequencies we can gauge the physical
and pathological state of an individual’s auditory system and thereby its
acoustic ability to negotiate its habitat.
The diversity of sound signals - there are around eighty cetacean species, every
one with a rich acoustic repertoire - complicates the task of extracting the key
components that determine the survival of an individual or a population, and is
a constraint on our ability to estimate the effects of contaminating sound
sources.
The BBVA Foundation project coordinated by Michel André has
developed analysis models for the sound signal sequences that sperm
whales emit while foraging in the ocean deeps, which conclude that
this marine mammal is capable of detecting a 25 cm squid at a distance
of more than two kilometers by means of the repeat emission of sonar
clicks. But the presence of intrusive, man-made sound sources can impair this
capacity, potentially disrupting the species in its feeding activities – occupying
80% of its time since its ingestion needs are a ton per day – and destabilizing
the entire food chain.
Each of the species making up the cetacean order has its own acoustic
repertoire directly related to the habitat where it has evolved over the course of
millions of years. In order to detect their prey, coastal species must be able to
accurately trace the outline and details of short-range features, while the
absence of such features in the high seas means the cetaceans that inhabit
them (pelagic species) have more need of medium- and long-range data on the
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presence of fish schools. However, all odontocetes or toothed cetaceans share
the same method of sound production, which includes the passage of air though
their nasal conducts and its expulsion by specialized tissues known as phonic
lips located in the upper part of the head. While the mammal is immersed, this
air is recycled and allows them to vocalize for the purpose of social
communication or echolocation, depending on the need at hand.
The absence of vocal chords is accompanied by another trait unique among the
mammals: that of not using an external auditory conduct for the purposes of
hearing. Instead, they pick up sound waves through their jaws which transmit
the information directly to the middle or inner ear where it is processed then
relayed to the brain.
The work of the BBVA Foundation project team will help develop bioindicators of
the damage caused by human-produced noise in the marine environment, as a
first step to combating this pollution source and establishing a balance between
the conduct of human activities and the conservation of marine mammals.
For further information, contact the BBVA Foundation Press Office
(+34 91 537 66 15 / +34 94 487 46 27)
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