Scholarly Journal ofOtolaryngology

ISSN: 2641-1709

DOI: 10.32474/SJO.2022.08.000299

Review Article

Prospects of Future Hearing Aids based on theBioacoustics System of Insects
Shahnoor Khan and Sharda Dhadse*
CSIR-National Environmental Engineering Research Institute, India*Corresponding Author: Sharda Dhadse, CSIR-National Environmental Engineering Research Institute, India
Received:

September 05, 2022

Published:

September 14, 2022

Abstract
New research initiatives in bioacoustics are shifting their attention away from the human ear and toward the biomechanics ofdiverse insects to advance hearing aid technology. Researchers have been examining several insects with effective sound delivery
and processing strategies to develop fresh, imaginative ideas for hearing aid technology. Nowadays, Researchers are trying to makea miniature directional Microphone, inspired by how some insects hear sound such as Mosquitoes and Drosophila. This miniature
directional earphone focuses the hearing aid on only the sound coming from in front of the user and reduces and controls unwanted
noise. The present review has discussed the auditory organ of insects and how the insect’s bioacoustics system helps develop futurehearing aids.

Introduction
Animals use a variety of signals to communicate, including
acoustic, optical, chemical, electrical, and tactile ones. Scientists
have long been fascinated by the processes involved in animalcommunication, as well as the reasons behind them. Bioacoustics isa branch of science that examines how sound is produced and how
it affects living things. To understand how sound is transferred tothe brain, the scientific community has devoted years to studying
the human ear. We can now investigate the auditory system morethoroughly than ever thanks to recent technological developments.
As a result, companies that specialize in hearing technology
are developing the most cutting-edge and potent therapies. for
those who are hard of hearing [1]. Numerous creatures, such as
crustaceans, arachnids, insects, fish, amphibians, reptiles, birds,and mammals, create species-specific acoustic signals during theireveryday lives [2].
New research initiatives are shifting their attention away fromthe human ear and toward the biomechanics of diverse insects toadvance hearing aid technology. Researchers have been examining
several insects with effective sound delivery and processing
strategies to develop fresh, imaginative ideas for hearing aid
Copyright © All rights are reserved by Sharda Dhadse.

technology. Cricket is one of the notable insects with which stiff andjagged wings, crickets can produce loud chirping sounds by rubbing
their wings together. We may mimic this concept by adjusting thestiffness of a speaker surface using powerful computer modelingsimulations (more frequently used to investigate aerodynamics)
and laser vibration devices [3]. This results in a quick and effective
method for amplifying the volume of tiny speakers. But insect
inspiration doesn’t end with tiny speakers. The operation of hearing
aids has typically been divided into phases. A microphone detects
sound signals, which are subsequently electrically amplified. Digitalprocessors are used to filter out unwanted sounds before a speakersends high-intensity sound directly into the ear canal. We might beable to learn from insects about each of these processes. To build amore potent hearing aid speaker, scientists are seeking to duplicate
these bioacoustics. This idea has been tested using computer
simulations and laser vibration [1].
Vertebrate animals have widespread hearing and acoustic
communication, but the only invertebrate group with widespreadsound production and hearing is insects. Several insect species
throughout the world depend on acoustics for mate selection,

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defense, and information transport, Human ears can easily detecta wide variety of insect sounds, with the sound of singing cicadasor grasshoppers being one of the most well-known insects [4].
Conspecific wingbeat sounds are picked up by mosquitoes, somehoneybees and, Drosophila species using Johnston’s organ in
their antennae. Research on these insects includes transduction
and amplification mechanisms similar to those found invertebrate hearing, functional and molecular diversifications ofmechanosensory cells, and complex mating duets that exceed thefrequency range of insect antennal ears [5]. This feature of insects
outlines potential avenues for future research on hearing aids forhuman betterment. Some insects, particularly those of the families
Gryllidae, Acrididae, Tettigoniidae (Orthoptera), and Cicadidae(Homoptera), evolved highly specialized auditory communication
mechanisms throughout evolution. Since insects’ audio
communication has a useful model for studying the mechanisms
used by living things to distinguish between complicated amplitudemodulated sounds, many laboratories are now interested in insects[6].
Acoustic system experts have been very interested in theauditory systems of insects for more than 50 years. The study ofthe insect ear has, however, only recently been able to take a more
meticulous approach because of technological advancements[7]. The locust, which has two sizable “tympanal” membranes
utilized for hearing on either side of its thorax, is one of the mostresearched insects in bioacoustics. Similar to a human ear drum,
these membranes vibrate in response to sound and transmit theTable 1: Different Types of Bioacoustics Organs found in Insects.

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ensuing impulses to the neurological system. With the peak of thewave directly above the location of the nerve cells, it generated atsunami-like vibration. In reality, the sound energy was greatly
amplified by this small change in thickness. Mammals’ fragile
middle ear bones enable the process of amplification, which locusts
mimic by merely altering the thickness of their eardrum. Scientists
are considering employing mechanisms like those found in thelocust’s advanced capacity to amplify incoming noises in hearing
aid microphones. Mosquitoes and fruit flies have small antennae on
their heads that are extremely sensitive to sound. Even though theresearch into these qualities is in its early stages, it may point us allin never untried directions for microphone design.

Auditory/ Hearing System in Insects

It is generally understood how humans make sounds andhear them, but very meager information is available about similarsystems in invertebrates, especially insects. Vibrations carriedthrough the air produce sound. An animal’s ability to “hear” implies
that it possesses one or more organs that can detect and understandthose air vibrations. The majority of insects have one or moresensory organs that can detect vibrations in the air. In addition tohearing, insects may be more sensitive to sound vibrations thanother animals. To communicate with other insects and to traverse
their environments, insects perceive and understand sounds. To
avoid being eaten by predators, some insects even listen to theirsounds. Hair sensilla, Antennal organ, cercal organs, and tympanalorgans are four types of insect auditory organs that have been
speculated to have hearing functions as shown in Table 1.

S. No

Bioacoustics Organs

Insects Example

1

Antennal organ (Johnston organ)

Mosquitoes, Fruit flies, honeybees, and hawk moths

3

Cercal organs

Crickets, Grasshopper and Cockroach2
4

Hair Sensilla (Setae)

Tympanic Membrane

Johnston Organ (Antennal organ): For some insects, theJohnston’s organ (Figure 1), a receptor that gathers auditory
data—is formed by a collection of sensory cells on the antennae.
These sensory cells sense the vibration of the segment(s) above
and are located on the pedicel, the second segment from the baseof the antennae. The flagellum is detected by Johnston’s organ to bemoving (third and typically final antennal segment). Each scolopidia,
which is arranged in the form of a bowl, contains a mechanosensory
chordotonal neuron [8,9]. The Johnston’s organ in the fruit flies
Drosophila melanogaster and Chironomus annularius contains
nearly 480 sensory neurons [10]. Fruit flies have a Johnston’s organthat can sense air vibrations brought on by a mate’s courtship song

Butterfly, Moths, Crickets, Grasshopper, etc
Cicadas, Grasshopper, Hymenopteransor wingbeat frequency. The Johnston’s organ can recognize thefrequency of a mate’s wing beats [8]. In hawk moths, the Johnston’sorgan regulates the stability of flight. The antennae vibrate at afrequency that corresponds to the wingbeat, according to kinematic
data collected from hovering moths during steady flight (27 Hz).
Apis mellifera (dancing honeybees) use sound signals sent into theair to identify the location of adjacent food sources. These signals
are made up of air molecules moving rapidly and rhythmically. The
Johnston’s organ in the pedicel of the antennae is used to detectand analyze these near-field sounds [11]. Through the Johnston’sorgans in their antennae and other mechanoreceptors, honeybees
can also be able to detect changes in electric fields.

Citation: Shahnoor Khan and Sharda Dhadse*. Prospects of Future Hearing Aids based on the Bioacoustics System of Insects. Sch J Oto.
8(5)-2022. SJO. MS.ID.000299. DOI: 10.32474/SJO.2022.08.000299

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Copyrights @ Sharda Dhadse

Figure 1: Mosquito Antenna showing Johnston organ.

Hair Sensilla (Setae)
On the body of insects, many specialized features appear toserve a sensory purpose. These include hair sensilla, comprised ofhair and a base section with a nerve supply. It has been proposedthat the hairs are sound sensors since they have been observed tovibrate in response to tones of particular frequencies. However,it appears more plausible that the sensilla serve to mediate thesense of touch and that their reaction to sound waves is merely

an incident of that activity. Setae, a small, stiff hair, (as shown inFigure 2) have been used by the larvae of Lepidoptera (butterfliesand moths) and Orthoptera (grasshoppers, crickets, etc.) to detectsound vibrations. Caterpillars frequently display defensive actions
in response to vibrations in the setae. Some will entirely cease
moving, while others could tense up and rear up in a combat stance.
Although many species have setae hairs, not all of them employ theorgans to detect sound vibrations.

Figure 2: Caterpillar head showing hair sensilla.

Cercal Organs
In insects like cockroaches and crickets, the cercal organ,
located at the back of the abdomen, as seen in Figure 3, is made up
of a broad brush with more than hundred fine hairs. When a brushis exposed to sound and an electrode is placed on the organ’s nerve
trunk, which has a robust nerve supply, a release of impulses can bemeasured. From below 100 hertz to possibly as high as 3,000 hertz,
the range of vibration frequencies where sensitivity is present is afairly wide. The response to sound waves up to 400 hertz have thesame frequency as the stimulus, as seen in cockroaches. Although

it is said that the cercal organ became quite sensitive, exact
measurements still need to be made.

Tympanic membrane

In insects, the tympanal organ (Figure 4) is made up of twoscolophores on either side of a thin, horny (chitinous) membranethat is attached to the surface of the body. One end of the scolophores
is frequently attached to the tympanic membrane, or eardrum, bya spinous process, while the other ends rest on an immovable partof the body structure. When the membrane vibrates in responseto the alternating pressures of sound waves, the ganglion cell

Citation: Shahnoor Khan and Sharda Dhadse*. Prospects of Future Hearing Aids based on the Bioacoustics System of Insects. Sch J Oto.
8(5)-2022. SJO. MS.ID.000299. DOI: 10.32474/SJO.2022.08.000299

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Volume 8 - Issue 5of the scolophore’s nerve fiber transfers impulses to the central
nervous system. This type of ear is a pressure ear because soundwaves pressure activates the tympanic membrane. Only two orfour components, or scolophores, can be found in simple tympanalorgans, as those seen in moths. On the other hand, cicadas havehighly developed versions of these organs that comprise a sensory

Copyrights @ Sharda Dhadsebody, which is an assembly of scolophores in a capsule that may
include up to 1,500 elements. The grasshopper ear, which hasreceived a more thorough examination than any other insect ear, isphysically similar to those of cicadas and moths and has between
80 and 100 scolophores.

Figure 3: Cercal organs with hairs of Cricket.

Figure 4: Tympanic membrane of Cicada and Grasshopper.
Normally, the base of the insect’s wing cover conceals thetympanic membrane. The sensory body, which is situated on theinside of the membrane, generates a bundle of auditory nerve fibres
that joins with nearby nerve fibres to form a long nerve that travels
to the ganglion in the thorax (nerve centre). At least seven distinct
insect groups have evolved specialized hearing tympanal organs.
The existence of a tympanal membrane typically distinguishes
tympanal organs (or eardrums). They have an air-filled cavity or
space behind them, and a chordotonal sensory organ innervatesthem [12]. Thus, these different auditory organs of insects havegiven new aspects for future hearing aids for many researchers andScientists. Nowadays, Researchers are trying to make a miniature
directional microphone designed in the style of some insects hearsound such as the mosquito microphone (Figure 5). This miniature
directional earphone focuses the hearing aid on only the soundcoming from in front of the user and reduces and controls unwanted
noise. The bioacoustics system of insects has given a new line ofresearch on the betterment of humans.

Citation: Shahnoor Khan and Sharda Dhadse*. Prospects of Future Hearing Aids based on the Bioacoustics System of Insects. Sch J Oto.
8(5)-2022. SJO. MS.ID.000299. DOI: 10.32474/SJO.2022.08.000299

936

Sch J Oto

Volume 8 - Issue 5

Copyrights @ Sharda Dhadse

Figure 5: Mosquito Microphone.

Conclusions
The human ear is the miracle of mechanical evolution. It enables
us to communicate and navigate the world. Additionally, it is simple
to harm and challenging to fix. Hearing aids continue to be bulky,unpleasant, and unable to produce full sounds. But from the worldof insects—we might be able to learn a new approach to restoring
our impaired hearing.
Engineering, biology, and medicine have always been very
distinct fields of study. However, by merging them, we might create
new engineering solutions based on findings discovered decadesago. Therefore, even though bio-inspired hearing aids might not
be poised to hit the market, this cutting-edge new field of study
may discover ever more ways to meet the needs of those who havehearing loss. Insects, the tiny mechanical specialists offer a wealthof further creative possibilities.

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4. Thomas R Neil, Marc W Holderied (2021) Chapter Two - Soundproduction and hearing in insects. Russell Jurenka (Eds.,), Advances inInsect Physiology, Academic Press, 61: 101-139.

Citation: Shahnoor Khan and Sharda Dhadse*. Prospects of Future Hearing Aids based on the Bioacoustics System of Insects. Sch J Oto.
8(5)-2022. SJO. MS.ID.000299. DOI: 10.32474/SJO.2022.08.000299

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Citation: Shahnoor Khan and Sharda Dhadse*. Prospects of Future Hearing Aids based on the Bioacoustics System of Insects. Sch J Oto.
8(5)-2022. SJO. MS.ID.000299. DOI: 10.32474/SJO.2022.08.000299

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