Bioacoustics is a cross-disciplinaryscience that combinesbiology andacoustics. Usually, it refers to the investigation ofsound production, dispersion and reception inanimals (includinghumans).[1] This involvesneurophysiological andanatomical basis of sound production and detection, and relation of acousticsignals to themedium they disperse through. The findings provide clues about theevolution of acoustic mechanisms, and from that, the evolution of animals that employ them.
Inunderwater acoustics andfisheries acoustics, the term is also used to mean the effect ofplants and animals on sound propagated underwater, usually in reference to the use ofsonar technology forbiomass estimation.[2][3] The study of substrate-borne vibrations used by animals is considered by some a distinct field calledbiotremology.[4]
For a long time, humans have employed animal sounds to recognise and find them. Bioacoustics as ascientific discipline was established by theSlovene biologistIvan Regen who began systematically to studyinsect sounds. In 1925, he used a specialstridulatory device to play in a duet with an insect. Later, he put a malecricket behind a microphone and female crickets in front of a loudspeaker. The females were not moving towards the male but towards the loudspeaker.[5] Regen's most important contribution to the field apart from realization that insects also detect airborne sounds was the discovery oftympanal organ's function.[6]
Relatively crude electro-mechanical devices available at the time (such asphonographs) allowed only for crude appraisal of signal properties. More accurate measurements were made possible in the second half of the 20th century by advances in electronics and utilization of devices such asoscilloscopes and digital recorders.
The most recent advances in bioacoustics concern the relationships among the animals and their acoustic environment and the impact of anthropogenicnoise. Bioacoustic techniques have recently been proposed as a non-destructive method for estimatingbiodiversity of an area.[7]
In the terrestrial environment, animals often use light for sensing distance, since light propagates well through air. Underwater sunlight only reaches to tens of meters depth. However, sound propagates readily through water and across considerable distances. Many marine animals can see well, but using hearing for communication, and sensing distance and location. Gauging the relative importance of audition versus vision in animals can be performed by comparing the number ofauditory andoptic nerves.
Since the 1950s to 1960s, studies on dolphin echolocation behavior using high frequency click sounds revealed that many different marine mammal species make sounds, which can be used to detect and identify species under water. Much research in bioacoustics has been funded bynaval research organizations, as biological sound sources can interfere withmilitary uses underwater.[8]
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, soanimal behaviour and the signals themselves are used for gaining insight into these processes.
Bioacoustics has also helped to pave the way for new emerging methods such as ecoacoustics (oracoustic ecology),[9] an interdisciplinary field of research that studies the sounds produced by ecosystems, including biological, geophysical and anthropogenic sources. It examines how these sounds interact with the environment, providing insights into biodiversity, habitat health and ecological processes. By analysing soundscapes, ecoacoustics helps monitor environmental changes, assess conservation efforts and detect human impacts on natural systems.
An experienced observer can use animal sounds to recognize a "singing" animalspecies, its location and condition in nature. 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 usualmicrophone, such as ahydrophone (for underwater sounds), detectors ofultrasound (very high-frequency sounds) orinfrasound (very low-frequency sounds), or alaser vibrometer (substrate-borne vibrational signals).Computers are used for storing and analysis of recorded sounds. Specialized sound-editingsoftware is used for describing and sorting signals according to theirintensity,frequency, duration and other parameters.
Animal sound collections, managed bymuseums of natural history and other institutions, are an important tool for systematic investigation of signals. Many effective automated methods involving signal processing, data mining, machine learning and artificial intelligence[10] techniques have been developed to detect and classify the bioacoustic signals.[11]
Scientists in the field of bioacoustics are interested in anatomy and neurophysiology oforgans involved in sound production and detection, including their shape,muscle action, and activity ofneuronal networks involved. Of special interest is coding of signals withaction potentials in the latter.
But since the methods used for neurophysiological research are still fairly complex and understanding of relevant processes is incomplete, more trivial methods are also used. Especially useful is observation of behavioural responses to acoustic signals. One such response isphonotaxis – directional movement towards the signal source. By observing response to well defined signals in a controlled environment, we can gain insight into signal function,sensitivity of the hearing apparatus,noise filtering capability, etc.
Biomass estimation is a method of detecting and quantifyingfish and other marine organisms usingsonar technology.[3] 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, andabundance. The basic components of the scientificecho sounder hardware function is to transmit the sound, receive, filter and amplify, record, and analyze the echoes. While there are many manufacturers of commercially available "fish-finders," quantitative analysis requires that measurements be made withcalibrated echo sounder equipment, having highsignal-to-noise ratios.
.jpg)
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 throughair and are detectable by the humanear).Katydid crickets, for example, communicate by sounds with frequencies higher than 100kHz, far into the ultrasound range.[12] Lower, but still in ultrasound, are sounds used bybats forecholocation. A segmented marine wormLeocratides kimuraorum produces one of the loudest popping sounds in the ocean at 157 dB, frequencies 1–100 kHz, similar to thesnapping shrimps.[13][14] On the other side of the frequency spectrum are low frequency-vibrations, often not detected byhearing organs, but with other, less specialized sense organs. The examples includeground vibrations produced byelephants whose principal frequency component is around 15 Hz, and low- to medium-frequency substrate-borne vibrations used by mostinsectorders.[15] Many animal sounds, however, do fall within the frequency range detectable by a human ear, between 20 and 20,000 Hz.[16] Mechanisms for sound production and detection are just as diverse as the signals themselves.
In a series of scientific journal articles published between 2013 and 2016,Monica Gagliano of theUniversity of Western Australia extended the science to includeplant bioacoustics.[17]
| International | |
|---|---|
| National | |
| Other | |
