Resonating device

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A resonating device is a structure used by an animal that improves the quality of its vocalizations through amplifying the sound produced via acoustic resonance. The benefit of such an adaptation is that the call's volume increases while lessening the necessary energy expenditure otherwise required to make such a sound. [1] [2] The resulting sound may also radiate more efficiently throughout the environment. [3]

Contents

The resonator may take the form of a hollow (a resonant space), a chamber (referred to as a resonating chamber), or an otherwise air-filled cavity (such as an air sac) which may be part of, or adjacent to, the animal's sound-producing organ, or it may be a structure entirely outside of the animal's body (part of the environment). Such structures use a similar principle to wind instruments, in that both utilize a resonator to amplify the soundwave that will ultimately be uttered.

Such structures are widespread throughout the animal kingdom, as sound production is important in the social lives of various animals. Arthropods developed their resonating devices from various parts of their anatomy; bony fish often utilize their swim bladders as a resonating chamber; various tetrapods developed resonating devices in parts of their respiratory tract, and evidence suggests that dinosaurs possessed them as well. Vocalizations produced through zoological resonating devices act as mating calls, territorial calls, and other communication calls.

In arthropods

Insects

Anatomy of male cicada, including vocal organs EB1911 cicada tymbal structure.png
Anatomy of male cicada, including vocal organs

Cicadas produce songs as part of their courtship display; the males of a number of species possess an abdomen that is largely hollow. [4] The sound producing organ, the tymbals, are connected to the abdomen, and as a consequence their calls are amplified significantly; [1] cicadas have been recorded to emit sounds of around 100 decibels, which is enough to cause hearing loss after 15 minutes. [5] [6] [7] [8] A large australian species, Cyclochila australasiae , produces sounds of up to 120 decibels at close range. [9] [10] In contrast, the basal hairy cicadas ( Tettigarcta ) do not emit an audible, airborne sound; like related leafhoppers, they instead transmit their vibrations through their substrate, turning the plants they perch upon into resonators. [9] [11]

A species of aquatic bug, Micronecta scholtzi , has been recorded to produce sounds of 105 dB, the "highest ratio dB/body size". This sound is produced via stridulation of the paramere (genital appendage) on an abdominal ridge, and may be amplified by reflections and refractions within the layer of trapped air the bug uses as an air supply, though the use of the air bubble as such has not been proven. [12] [7]

Tree crickets (specifically, Oecanthus henryi ) were found to create baffles by selecting appropriately sized leaves, then chewing a hole near the centre that was about the size of their wings. By calling from inside of these baffles, they were able to prevent acoustic short-circuiting and effectively increasing the loudness of its calls. [13]

In osteichthyans

Bony fish possess an air-filled organ called the swim bladder that is primarily used to regulate buoyancy. However, a number of species have adapted their swimbladders to be a part of a sound-producing organ. The sound-producing apparatus consists of fast-contracting striated muscles that vibrate the swim bladder, either entirely attached to the swimbladder or also attaching to adjacent structures like the vertebral column or occipital bones. [14]

Other families of fish which have sound-generating mechanisms involving the swim bladder include: [14]

In amphibians

Frogs possess vocal sacs which serve to enhance their nuptial calls. To call, the frog closes its mouth, then expels air from its lungs, through its larynx, and into the vocal sac; the larynx's vibration causes the vocal sac to resonate. [20] [21] [22] Additionally, some frogs may call from inside structures that further amplify their calls; Metaphrynella sundana call from inside tree hollows with water pooling at the bottom, tuning their own calls to the resonant frequency of their specific tree hollow. [23] Mientien tree frogs ( Kurixalus idiootocus ) residing in urban areas utilize storm drains to improve their calls; frogs calling within the drains called louder and for longer periods. [24]

In amniotes

Mammals

Primates

Laryngeal air sacs of nonhuman primates PrimateAirSacs Schematic.png
Laryngeal air sacs of nonhuman primates

The larynx is the primary vocal organ of mammals. In humans, it acts as a resonator only for high frequencies, due to its small volume; the pharynx, oral-, and nasal cavities, descending in order, are the most important resonators in humans. [25] [26] [27]

Several non-human primates are adapted to producing loud calls, and they often rely on resonance chambers to produce it. The howler monkeys possess extralaryngeal airsacs along with a pneumatized (hollow) hyoid bone; it is suggested that the hollow hyoid acts as a resonating chamber, allowing the howler monkey to produce its namesake call. [28] [29] Gibbons are also well known for their loud territorial calls; [30] [31] the siamang has a particularly well developed gular sac that acts as a resonating chamber. [32] Male orangutans also use their throat pouches for the purpose of enhancing their calls. [33] [34]

Male gorillas' airways have air sacs that penetrate into the soft tissue of the chest. These airsacs amplify the sound produced by his percussive chest-beating. [28]

Laurasiatheres

Internal organs of the hammerhead bat. Hypsignathus monstrosus side cross section.png
Internal organs of the hammerhead bat.

Horseshoe bats (of the family Rhinolophidae) are a bat genus that possess air pouches, or chambers, around their larynx which act as Helmholtz resonators. [1] The male hammerhead bat has an extremely large larynx that extends through most of his thoracic cavity, displacing his other internal organs. [35] A pharyngeal air sac connects to a large sinus in the bat's snout; these structures act as resonating chambers to further amplify the bat's voice. [36] So specialized are these structures that scientists Herbert Lang and James Chapin remarked; "In no other mammal is everything so entirely subordinated to the organs of voice". [37]

Pinnipeds have been noted to employ this structure; the expanded nasal chambers of elephant and hooded seals act as resonant spaces that enhance their calls. The expanded laryngeal lumen of California sea lions, the pharyngeal pouch of walrus, and the tracheal sacs of various phocids may also function in a similar manner. [38]

Mysticetes, such as the blue whale, use their greatly expanded larynx as a resonant cavity. [28] Even in juveniles, the larynx is bigger than either one of the whale's lungs. This organ, along with the nasal passages, act as resonant spaces that produce the signature drawn-out calls of the baleen whales. [38]

Sauropsida

Crocodylians

The ghara of the indian gharial is a specialized organ that acts as a resonating chamber; as a result, the call of a mature male can be heard up to 75 metres (82 yd) away. [39] [40]

Lambeosaurines

The crests of a number of lambeosaurine dinosaurs have been hypothesized to act as resonating chambers; reconstructed upper airways, specifically, the nasal passsages of Parasaurolophus , Lambeosaurus , Hypacrosaurus and Corythosaurus have been examined, and they were concluded to be able to enhance the vocalizations in life, and the different cranial crest shapes would have distinguished the sounds produced between genera. [41] [42] [43] [44]

Birds

The avian syrinx is the primary vocal organ in most birds, [45] with the trachea being the primary resonator in the system. In some birds, the trachea is grossly elongated, coiling or looping within the thorax; the trumpet manucode's trachea is 20 times longer than is predicted for birds of a comparable size. This condition of tracheal elongation (TE) is known in several orders of birds, and it seems to have been evolved independently a number of times. W. T. Fitch hypothesizes that the function of such elongated trachea in birds may be to "exaggerate its apparent [body] size", through the lowering of the frequency (Hz) of its calls; larger individuals are preferentially selected as mates, and thus a "deeper" voice is selected for. Additionally, lower frequency calls travel further, attracting mates from a wider area. [46]

Additionally, the air sac system, which is part of the respiratory system in birds, may be an important resonator in certain birds, as is the inflated crop of columbiform pigeons and doves. [47]

Related Research Articles

<span class="mw-page-title-main">Human voice</span> Sound made by a human being using the vocal tract

The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound production in which the vocal folds are the primary sound source.

<span class="mw-page-title-main">Larynx</span> Voice box, an organ in the neck of amphibians, reptiles, and mammals

The larynx, commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about 4–5 centimeters in diameter. The larynx houses the vocal cords, and manipulates pitch and volume, which is essential for phonation. It is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The word 'larynx' comes from the Ancient Greek word lárunx ʻlarynx, gullet, throatʼ.

<span class="mw-page-title-main">Trachea</span> Cartilaginous tube that connects the pharynx and larynx to the lungs

The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all animals lungs. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea, the cricoid cartilage attaches it to the larynx. The trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying ligaments, and by the trachealis muscle at their ends. The epiglottis closes the opening to the larynx during swallowing.

<span class="mw-page-title-main">Microbat</span> Suborder of bats

Microbats constitute the suborder Microchiroptera within the order Chiroptera (bats). Bats have long been differentiated into Megachiroptera (megabats) and Microchiroptera, based on their size, the use of echolocation by the Microchiroptera and other features; molecular evidence suggests a somewhat different subdivision, as the microbats have been shown to be a paraphyletic group.

<span class="mw-page-title-main">Swim bladder</span> Gas-filled organ that contributes to the ability of a fish to control its buoyancy

The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift via swimming, which expends more energy. Also, the dorsal position of the swim bladder means that the expansion of the bladder moves the center of mass downwards, allowing it to act as a stabilizing agent in some species. Additionally, the swim bladder functions as a resonating chamber, to produce or receive sound.

<span class="mw-page-title-main">Respiratory tract</span> Organs involved in transmission of air to and from the point where gases diffuse into tissue

The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa.

<span class="mw-page-title-main">Resonator</span> Device or system that exhibits resonance

A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies. The oscillations in a resonator can be either electromagnetic or mechanical. Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal. Musical instruments use acoustic resonators that produce sound waves of specific tones. Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency.

<span class="mw-page-title-main">Vocal sac</span> Noise-producing organ in frogs and toads

The vocal sac is the flexible membrane of skin possessed by most male frogs and toads. The purpose of the vocal sac is usually as an amplification of their mating or advertisement call. The presence or development of the vocal sac is one way of externally determining the sex of a frog or toad in many species; taking frogs as an example;

<span class="mw-page-title-main">Syrinx (bird anatomy)</span> The vocal organ of birds

The syrinx is the vocal organ of birds. Located at the base of a bird's trachea, it produces sounds without the vocal folds of mammals. The sound is produced by vibrations of some or all of the membrana tympaniformis and the pessulus, caused by air flowing through the syrinx. This sets up a self-oscillating system that modulates the airflow creating the sound. The muscles modulate the sound shape by changing the tension of the membranes and the bronchial openings. The syrinx enables some species of birds to mimic human speech.

<span class="mw-page-title-main">Helmholtz resonance</span> Phenomenon of air resonance in a cavity

Helmholtz resonance, also known as wind throb, refers to the phenomenon of air resonance in a cavity, an effect named after the German physicist Hermann von Helmholtz. This type of resonance occurs when air is forced in and out of a cavity, causing the air inside to vibrate at a specific natural frequency. The principle is widely observable in everyday life, notably when blowing across the top of a bottle, resulting in a resonant tone.

<span class="mw-page-title-main">Animal song</span>

Animal song is not a well-defined term in scientific literature, and the use of the more broadly defined term vocalizations is in more common use. Song generally consists of several successive vocal sounds incorporating multiple syllables. Some sources distinguish between simpler vocalizations, termed “calls”, reserving the term “song” for more complex productions. Song-like productions have been identified in several groups of animals, including cetaceans, avians (birds), anurans (frogs), and humans. Social transmission of song has been found in groups including birds and cetaceans.

Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization in their bones. Birds use air sacs for respiration as well as a number of other things. Theropods, like Aerosteon, have many air sacs in the body that are not just in bones, and they can be identified as the more primitive form of modern bird airways. Sauropods are well known for the large number of air pockets in their bones, although one theropod, Deinocheirus, shows a rivalling number of air pockets.

An acoustic guitar is a musical instrument in the string family. When a string is plucked, its vibration is transmitted from the bridge, resonating throughout the top of the guitar. It is also transmitted to the side and back of the instrument, resonating through the air in the body, and producing sound from the sound hole. While the original, general term for this stringed instrument is guitar, the retronym 'acoustic guitar' – often used to indicate the steel stringed model – distinguishes it from an electric guitar, which relies on electronic amplification. Typically, a guitar's body is a sound box, of which the top side serves as a sound board that enhances the vibration sounds of the strings. In standard tuning the guitar's six strings are tuned (low to high) E2 A2 D3 G3 B3 E4.

<span class="mw-page-title-main">Mouth</span> First portion of the alimentary canal that receives food

The mouth is the body orifice through which many animals ingest food and vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity, is also the first part of the alimentary canal, which leads to the pharynx and the gullet. In tetrapod vertebrates, the mouth is bounded on the outside by the lips and cheeks — thus the oral cavity is also known as the buccal cavity — and contains the tongue on the inside. Except for some groups like birds and lissamphibians, vertebrates usually have teeth in their mouths, although some fish species have pharyngeal teeth instead of oral teeth.

<span class="mw-page-title-main">Túngara frog</span> Species of amphibian

The túngara frog is a species of frog in the family Leptodactylidae. It is a small nocturnal terrestrial frog found in Mexico, Central America, and the northeastern regions of South America.

<i>Thopha saccata</i> Australian species of cicada

Thopha saccata, the double drummer, is the largest Australian species of cicada and reputedly the loudest insect in the world. Documented by the Danish zoologist Johan Christian Fabricius in 1803, it was the first described and named cicada native to Australia. Its common name comes from the large dark red-brown sac-like pockets that the adult male has on each side of its abdomen—the "double drums"—that are used to amplify the sound it produces.

Frogs 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 calls by return calling, by approach, and by going silent. These responses have been shown to be important for species recognition, mate assessment, and localization. Beginning with the pioneering experiments of Robert Capranica in the 1930s using playback techniques with normal and synthetic calls, behavioral biologists and neurobiologists have teamed up to use frogs and toads as a model system for understanding the auditory function and evolution. It is now considered an important example of the neural basis of animal behavior, because of the simplicity of the sounds, the relative ease with which neurophysiological recordings can be made from the auditory nerve, and the reliability of localization behavior. Acoustic communication is essential for the frog's survival in both territorial defense and in localization and attraction of mates. Sounds from frogs travel through the air, through water, and through the substrate. Frogs and toads largely ignore sounds that are not conspecific calls or those of predators, with only louder noises startling the animals. Even then, unless major vibration is included, they usually do not take any action unless the source has been visually identified. The neural basis of communication and audition gives insights into the science of sound applied to human communication.

Vocal resonance may be defined as "the process by which the basic product of phonation is enhanced in timbre and/or intensity by the air-filled cavities through which it passes on its way to the outside air." Throughout the vocal literature, various terms related to resonation are used, including: amplification, filtering, enrichment, enlargement, improvement, intensification, and prolongation. Acoustic authorities would question many of these terms from a strictly scientific perspective. However, the main point to be drawn from these terms by a singer or speaker is that the result of resonation is to make a better sound, or at least suitable to a certain esthetical and practical domain.

<span class="mw-page-title-main">Roar</span> Deep resonating sound produced by animals

A roar is a type of animal vocalization that is loud, deep and resonating. Many mammals have evolved to produce roars and other roar-like vocals for purposes such as long-distance communication and intimidation. These include various species of big cats, bears, pinnipeds, deer, bovids, elephants and simians.

A mating call is the auditory signal used by animals to attract mates. It can occur in males or females, but literature is abundantly favored toward researching mating calls in females. In addition, mating calls are often the subject of mate choice, in which the preferences of one gender for a certain type of mating call can drive sexual selection in a species. This can result in sympatric speciation of some animals, where two species diverge from each other while living in the same environment.

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