Bioacoustics
Encyclopedia
Bioacoustics is a cross-disciplinary science
that combines biology
and acoustics
. Usually it refers to the investigation of sound
production, dispersion through elastic media
, and reception in animal
s, including humans. This involves neurophysiological
and anatomical
basis of sound production and detection, and relation of acoustic signals
to the medium
they disperse through. The findings give us some evidence 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
who began systematically to study insect
sounds. In 1925 he used a special stridulatory
device to play in a duet with an insect. Later he put a male Cricket (insect)
behind a microphone and female crickets in front of a loudspeaker. The females were not moving towards the male but towards the loudspeaker. 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.
Relatively crude electro-mechanical devices available at the time (such as phonograph
s) 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 as oscilloscope
s and digital recorders.
The most recent advances in bioacoustics concern the relationships among the animals and their acoustic environment and the impact of anthropogenic noise. Bioacoustic techniques have recently been proposed as a non-invasive method for estimating biodiversity
.
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.
An experienced observer can use animal sounds to recognize a "singing" animal species, 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 usual microphone
, such as a hydrophone
(for underwater sounds), an ultrasound
detector (very high-frequency
sounds), or a laser vibrometer
(substrate-borne vibrational signals). Computer
s 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.
Animal sound collections, managed by museums of natural history
and other institutions, are an important tool for systematic investigation of signals.
s 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. Of special interest is coding of signals with action potential
s 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 is 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, sensitivity
of the hearing apparatus, noise
filtering capability, etc.
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 analyze the echoes. While there are many manufacturers of commercially available "fish-finders," quantitative analysis requires that measurements be made with calibrated
echo sounder equipment, having high signal-to-noise ratio
s.
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 strict sense of the word, i.e. compression waves that propagate through air and are detectable by the human ear
. Katydid cricket
s, 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 bat
s 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
. Many animal sounds, however, do fall within the frequency range detectable by a human ear, between 50 and 15,000 Hz. Mechanisms for sound production and detection are just as diverse as the signals themselves.
Science
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...
that combines biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
and acoustics
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
. Usually it refers to the investigation of sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
production, dispersion through elastic media
Transmission medium
A transmission medium is a material substance that can propagate energy waves...
, and reception in animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s, including humans. This involves neurophysiological
Neurophysiology
Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...
and anatomical
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
basis of sound production and detection, and relation of acoustic signals
Signal (electrical engineering)
In the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
to the medium
Transmission medium
A transmission medium is a material substance that can propagate energy waves...
they disperse through. The findings give us some evidence about the evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
of acoustic mechanisms, and from that, the evolution of animals that employ them.
In underwater acoustics
Underwater acoustics
Underwater acoustics is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water and its boundaries. The water may be in the ocean, a lake or a tank. Typical frequencies associated with underwater acoustics are between 10 Hz and...
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
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
technology for biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
estimation
History
For a long time humans have employed animal sounds to recognise and find them. Bioacoustics as a scientific discipline was established by the Slovene biologist Ivan RegenIvan Regen
Ivan Regen was a Slovenian biologist, best known for his studies in the field of bioacoustics....
who began systematically to study insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
sounds. In 1925 he used a special stridulatory
Stridulation
Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fishes, snakes and spiders...
device to play in a duet with an insect. Later he put a male Cricket (insect)
Cricket (insect)
Crickets, family Gryllidae , are insects somewhat related to grasshoppers, and more closely related to katydids or bush crickets . They have somewhat flattened bodies and long antennae. There are about 900 species of crickets...
behind a microphone and female crickets in front of a loudspeaker. The females were not moving towards the male but towards the loudspeaker. Regen's most important contribution to the field apart from realization that insects also detect airborne sounds was the discovery of tympanal organ
Tympanal organ
A tympanal organ is a hearing organ in insects, consisting of a membrane stretched across a frame backed by an air sac and associated sensory neurons...
's function.
Relatively crude electro-mechanical devices available at the time (such as phonograph
Phonograph
The phonograph record player, or gramophone is a device introduced in 1877 that has had continued common use for reproducing sound recordings, although when first developed, the phonograph was used to both record and reproduce sounds...
s) 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 as oscilloscope
Oscilloscope
An oscilloscope is a type of electronic test instrument that allows observation of constantly varying signal voltages, usually as a two-dimensional graph of one or more electrical potential differences using the vertical or 'Y' axis, plotted as a function of time,...
s and digital recorders.
The most recent advances in bioacoustics concern the relationships among the animals and their acoustic environment and the impact of anthropogenic noise. Bioacoustic techniques have recently been proposed as a non-invasive method for estimating biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
.
Methods in bioacoustics
Animal behaviour
Animal behaviour is the subject of:* The field of Ethology* Animal Behaviour, a scientific journal...
and the signals themselves are used for gaining insight into these processes.
Acoustic signals
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
, such as a hydrophone
Hydrophone
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
(for underwater sounds), an ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
detector (very high-frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
sounds), or a laser vibrometer
Laser Doppler Vibrometer
A laser Doppler vibrometer is a scientific instrument that is used to make non-contact vibration measurements of a surface. The laser beam from the LDV is directed at the surface of interest, and the vibration amplitude and frequency are extracted from the Doppler shift of the laser beam...
(substrate-borne vibrational signals). Computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s are used for storing and analysis of recorded sounds. Specialized sound-editing software is used for describing and sorting signals according to their intensity
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
, frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, duration and other parameters.
Animal sound collections, managed by museums of natural history
Museum of Natural History
A museum of natural history is a museum with exhibits about natural history, including such topics as animals, plants, ecosystems, geology, paleontology, and climatology. Some museums feature natural-history collections in addition to other collections, such as ones related to history, art and...
and other institutions, are an important tool for systematic investigation of signals.
Sound production, detection, and use in animals
ScientistScientist
A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...
s in the field of bioacoustics are interested in anatomy and neurophysiology of organs
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
involved in sound production and detection, including their shape, muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
action, and activity of neuronal networks involved. Of special interest is coding of signals with action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
s 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 is 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, sensitivity
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
of the hearing apparatus, noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
filtering capability, etc.
Biomass estimation
Biomass estimation is a method of detecting and quantifying fishFish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and other marine organisms using sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
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
Abundance (ecology)
Abundance is an ecological concept referring to the relative representation of a species in a particular ecosystem. It is usually measured as the large number of individuals found per sample...
. The basic components of the scientific echo sounder hardware
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
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 with calibrated
Calibration
Calibration is a comparison between measurements – one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device....
echo sounder equipment, having high signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
s.
Animal sounds
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
. Katydid cricket
Tettigoniidae
The family Tettigoniidae, known in American English as katydids and in British English as bush-crickets, contains more than 6,400 species. It is part of the suborder Ensifera and the only family in the superfamily Tettigonioidea. They are also known as long-horned grasshoppers, although they are...
s, for example, communicate by sounds with frequencies higher than 100 kHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, far into the ultrasound range. Lower, but still in ultrasound, are sounds used by bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s for echolocation. On the other side of the frequency spectrum are low frequency-vibrations, often not detected by hearing
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
organs, but with other, less specialized sense organs. The examples include ground vibrations
Ground vibrations
Ground vibrations is a technical term that is being used to describe mostly man-made vibrations of the ground, in contrast to natural vibrations of the Earth studied by seismology. For example, vibrations caused by explosions, construction works, railway and road transport, etc - all belong to...
produced by elephants whose principal frequency component is around 15 Hz, and low- to medium-frequency substrate-borne vibrations used by most insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
orders
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
. Many animal sounds, however, do fall within the frequency range detectable by a human ear, between 50 and 15,000 Hz. Mechanisms for sound production and detection are just as diverse as the signals themselves.
See also
- Acoustic ecologyAcoustic ecologyAcoustic ecology, sometimes called ecoacoustics or soundscape studies, is the relationship, mediated through sound, between living beings and their environment. Acoustic ecology studies started in the late 1960s with R. Murray Schafer and his team at Simon Fraser University as part of the World...
- Acoustical oceanographyAcoustical oceanographyAcoustical oceanography is the use of underwater sound to study the sea, its boundaries and its contents.-History:The earliest and most widespread use of sound and sonar technology to study the properties of the sea is the use of an echo sounder to measure water depth...
- Animal communicationAnimal communicationAnimal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...
- Animal languageAnimal languageAnimal language is the modeling of human language in non human animal systems. While the term is widely used, researchers agree that animal languages are not as complex or expressive as human language....
- BiomusicBiomusicBiomusic is a form of experimental music which deals with sounds created or performed by non-humans. The definition is also sometimes extended to included sounds made by humans in a directly biological way...
- Diffusion (acoustics)Diffusion (acoustics)Diffusion, in acoustics and architectural engineering, is the efficacy by which sound energy is spread evenly in a given environment. A perfectly diffusive sound space is one that has certain key acoustic properties which are the same anywhere in the space. A non-diffuse sound space would have...
- EcoacousticsEcoacousticsEcoacoustics is a relatively new cross-diciplinary science that involves ecology and acoustics. It differs from the closely related field of bioacoustics, measuring the acoustic properties of a whole environment in order to better understand the complex dynamics of an ecosystem...
- Field recordingField recordingField recording is the term used for an audio recording produced outside of a recording studio. The recording is typically recorded in the same channel format as the desired result, for instance, stereo recording equipment will yield a stereo product...
- Frog hearing and communicationFrog hearing and communicationFrogs and toads produce a rich variety of sounds, calls, and songs during their courtship and mating rituals. The callers, usually males, make stereotyped sounds in order to advertise their location, their mating readiness and their willingness to defend their territory; listeners respond to the...
- List of animal sounds
- Music therapyMusic therapyMusic therapy is an allied health profession and one of the expressive therapies, consisting of an interpersonal process in which a trained music therapist uses music and all of its facets—physical, emotional, mental, social, aesthetic, and spiritual—to help clients to improve or maintain their...
- Natural soundsNatural soundsNatural sounds include animal sounds, from the chirruping of crickets to the vocalisations of mammals. They also include the sounds of other natural phenomena, such as water sounds; for example, the sound of rain falling on the ground or on water, the sound of a waterfall, a rushing river, waves...
- Underwater acousticsUnderwater acousticsUnderwater acoustics is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water and its boundaries. The water may be in the ocean, a lake or a tank. Typical frequencies associated with underwater acoustics are between 10 Hz and...
- Vocal learningVocal learningVocal learning is the ability of animals to modify vocal signals in form as a result of experience with those of other individuals. This can lead to signals that are either similar or dissimilar to the model...
- Whale songWhale songWhale sounds are the sounds made by whales and which are used for different kinds of communication.The word "song" is used to describe the pattern of regular and predictable sounds made by some species of whales, notably the Humpback Whale...
- ZoomusicologyZoomusicologyZoomusicology is a field of musicology and zoology or more specifically, zoosemiotics. Zoomusicology is the study of the music of animals, or rather the musical aspects of sound or communication produced and received by animals....
External links
- The British Library Sound Archive has 150,000 recordings of over 10,000 species.
- International Bioacoustics Council links to many bioacoustics resources.
- Borror Laboratory of Bioacoustics at The Ohio State University has a large archive of animal sound recordings.
- Listen to Nature 400 examples of animal songs and calls
- Wildlife Sound Recording Society
- Bioacoustic Research Program at the Cornell Lab of Ornithology distributes a number of different free bioacoustics synthesis & analysis programs.
- Macaulay Library at the Cornell Lab of Ornithology is the world's largest collection of animal sounds and associated video.
Further reading
- Ewing A.W. (1989): Arthropod bioacoustics: Neurobiology and behaviour. Edinburgh: Edinburgh Universitsy Press. ISBN 0-7486-0148-1
- Fletcher N. (2007): Animal Bioacoustics. IN: Rossing T.D. (ed.): Springer Handbook of Acoustics, SpringerSpringer Science+Business Media- Selected publications :* Encyclopaedia of Mathematics* Ergebnisse der Mathematik und ihrer Grenzgebiete * Graduate Texts in Mathematics * Grothendieck's Séminaire de géométrie algébrique...
. ISBN 978-0-387-33633-6