BIOACOUSTIC

ABHISHEK JHA

GROUP 20

INTRODUCTION

Is a cross- disciplinary science that combine Biology and Acoustics.

Usually it refers to the investigation of sound production, dispersion and reception in Animal(including human).

This involves  neurophysiological and anatomical basis of sound production and detection, and relation of acoustic sound to the medium they disperse through.

The findings provide clues about the evolution of acoustic mechanisms and from that the evolution of animals that employ them.

In underwater acoustics and fisheries acoustics the term is also used to mean the effect of plants and animals on sound propagated underwater usually in reference to the use of sonar technology for biomass estimation.

HISTORY  Bioacoustics as a scientific discipline was established

by the Slovene biologist Ivan Regen who began systematically to study insect sounds.

 In 1925 he used a special stridulatory device to play in a duet with an insect.

Regen's most important contribution to the field apart from realization that insects also detect airborne sounds was the discovery of tympanal organ's function.

Methods in bioacoustics

Listening is still one of the main methods used in bioacoustical research.

Little is known about neurophysiological processes that play a role in production, detection and interpretation of sounds in animals, so animal behaviour and the signals themselves are used for gaining insight into these processes.

1. ACOUSTIC SIGNALS

2. SOUND PRODUCTION,DETECTION AND USE IN ANIMALS

3. BIOMASS ESTIMATION

THREE METHODS OF BIOACOUSTICS

Acoustic signals

 Investigation of animal sounds also includes signal recording with electronic recording equipment.

Due to the wide range of signal properties and media they propagate through, specialized equipment may be required instead of the usual microphone, such as a hydrophone (for underwater sounds), detectors of ultrasound (very high-frequency sounds) or infrasound (very low-frequency sounds), or a laser vibrometer (substrate-borne vibrational signals).

Computer are used for storing and analysis of recorded sounds. 

Specialized sound-editing software  is used for describing and sorting signals according to their intensity, frequency duration and other parameters.

Sound production, detection and use in animals

Scientists in the field of bioacoustics are interested in anatomy and neurophysiology of organs involved in sound production and detection, including their shape, muscle action, and activity of neuronal networks involved.

 Phonotaxy -- directional movement towards the signal source. By observing response to well defined signals in a controlled environment, we can gain insight into signal function.

Biomass estimation

Biomass estimation is a method of detecting and quantifying fish and other marine organisms using sonar technology.

As the sound pulse travels through water it encounters objects that are of different density than the surrounding medium, such as fish, that reflect sound back toward the sound source.

These echoes provide information on fish size, location and abundance.

The basic components of the scientific echo sounder hardware function is to transmit the sound, receive, filter and amplify, record and analyse the echoes. 

Animal sounds

Sounds used by animals that fall within the scope of bioacoustics include a wide range of frequencies and media, and are often not "sound" in the narrow sense of the word (i.e. compression waves that propagate through air and are detectable by the human ear).

Katydid crickets for example, communicate by sounds with frequencies higher than 100 kHz, far into the ultrasound range.

Lower, but still in ultrasound, are sounds used by bats for echolocation.

On the other side of the frequency spectrum are low frequency-vibrations, often not detected by hearing organs, but with other, less specialized sense organs.

The examples include ground vibrations produced by elephants whose principal frequency component is around 15 Hz, and low- to medium-frequency substrate-borne vibrations used by most insect orders.

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