Sound Sound

Why sound is a useful and versatile form of Why sound is a useful and versatile form of

communicationcommunication Sound is a form of energy that travels in waves. Sound waves can be compared by Sound is a form of energy that travels in waves. Sound waves can be compared by

determining their frequency. Sound requires a medium such as solid, liquid or gas determining their frequency. Sound requires a medium such as solid, liquid or gas through which to travel. It cannot travel through a vacuum. through which to travel. It cannot travel through a vacuum.

Sound is a useful for communication to many because of the enormous variety of Sound is a useful for communication to many because of the enormous variety of sounds that can be produced. Sound is useful both day and night. It travels over long sounds that can be produced. Sound is useful both day and night. It travels over long distances and can go around corners. Sound is also versatile because variation can distances and can go around corners. Sound is also versatile because variation can occur in the actual sound or the loudness of the sound, and the pitch and duration of occur in the actual sound or the loudness of the sound, and the pitch and duration of a message can be readily changeda message can be readily changed

Advantages of sound communication:Advantages of sound communication: A variety of sounds can be made by an individualA variety of sounds can be made by an individual Sound travels well in both air and waterSound travels well in both air and water The sender does not have to be visible to the receiverThe sender does not have to be visible to the receiver It is useful at night and in dark environmentsIt is useful at night and in dark environments Sound can go around objectsSound can go around objects It provides directional informationIt provides directional information It works over long distancesIt works over long distances

How is sound produced?How is sound produced? Sound is a form of energy that requires a medium. It Sound is a form of energy that requires a medium. It

cannot travels in a vacuum. It is a longitudinal wave cannot travels in a vacuum. It is a longitudinal wave where the particles move backwards and forwards in the where the particles move backwards and forwards in the direction of the wave. Sound is a form of energy direction of the wave. Sound is a form of energy produced by an object that vibrates. produced by an object that vibrates.

The vibrating object causes nearby air molecules to The vibrating object causes nearby air molecules to vibrate back and forth, and these molecules causes vibrate back and forth, and these molecules causes other to vibrate at the same frequency. This results in a other to vibrate at the same frequency. This results in a compression wave, which travels through a medium. The compression wave, which travels through a medium. The frequency of the vibration of air molecules is the same as frequency of the vibration of air molecules is the same as the frequency of the vibrating object.the frequency of the vibrating object.

The structure of the human The structure of the human larynxlarynx

The larynx or voice box lies directly below The larynx or voice box lies directly below the tongue and soft palate. Inside the the tongue and soft palate. Inside the larynx are the vocal cords, which consist of larynx are the vocal cords, which consist of muscles, which can adjust pitch by altering muscles, which can adjust pitch by altering their position and tension. their position and tension.

Together, the larynx, tongue and hard and Together, the larynx, tongue and hard and soft palate make speech possible. When soft palate make speech possible. When air passes over the vocal cords in the air passes over the vocal cords in the larynx, they produce sounds that can be larynx, they produce sounds that can be altered by the tongue, together with the altered by the tongue, together with the hard and soft palate, the teeth and the lipshard and soft palate, the teeth and the lips

Outline and compare the detection of Outline and compare the detection of vibrations by insects, fish and mammalsvibrations by insects, fish and mammals

InsectsInsects

Insects have hearing organs in many different parts of their bodies. Insects have hearing organs in many different parts of their bodies. Three main types of sound detection organs in insects are:Three main types of sound detection organs in insects are:

Tympanic organs - consists of a membrane stretched across an air sac. In Tympanic organs - consists of a membrane stretched across an air sac. In grasshoppers, tympanic organs are located on the legs. When sound waves grasshoppers, tympanic organs are located on the legs. When sound waves reach the tympanic organ the membrane vibrates and this stimulates the hair reach the tympanic organ the membrane vibrates and this stimulates the hair cells and a message is sent via nerve to the brain.cells and a message is sent via nerve to the brain.

Auditory hairs - Many insects are covered with auditory hairs that are sensitive to Auditory hairs - Many insects are covered with auditory hairs that are sensitive to sound waves. These hairs have different lengths and stiffness and respond to sound waves. These hairs have different lengths and stiffness and respond to vibrations at different frequencies. The hairs are particularly abundant on the vibrations at different frequencies. The hairs are particularly abundant on the antennae and legs.antennae and legs.

Vibration receptors - Insects that fly at night have adaptations that can detect Vibration receptors - Insects that fly at night have adaptations that can detect ultrasonic sound produced by bats. Hawk moths can hear ultrasonic sound ultrasonic sound produced by bats. Hawk moths can hear ultrasonic sound through two sets of modified mouthparts.through two sets of modified mouthparts.

FishFish

Fish have several organs to detect sound waves. These include:Fish have several organs to detect sound waves. These include:

Internal ears - Fish have an ear but unlike mammals, there is no external Internal ears - Fish have an ear but unlike mammals, there is no external opening or an eardrum. Otoliths and the labyrinth make up the inner ear opening or an eardrum. Otoliths and the labyrinth make up the inner ear of fish. The movement of otolith across sensory hair cells is interpreted of fish. The movement of otolith across sensory hair cells is interpreted as sound by fish.as sound by fish.

Lateral line organ - visible line along the body of fish. It consists of fluid-Lateral line organ - visible line along the body of fish. It consists of fluid-filled canals that are collections of sensory hairs called neuromasts. filled canals that are collections of sensory hairs called neuromasts. These respond to low frequency sound. The neuromast consists of hair These respond to low frequency sound. The neuromast consists of hair cells that detect vibration in the surrounding watercells that detect vibration in the surrounding water

Swim bladder - primarily responsible for equalizing pressure between the Swim bladder - primarily responsible for equalizing pressure between the surrounding water and the fish. It acts as an amplifier to any sound, surrounding water and the fish. It acts as an amplifier to any sound, passing the vibrations directly onto the inner ear.passing the vibrations directly onto the inner ear.

Mammals Mammals

Mammals have ears to detect sound. Sound enters the ear, and Mammals have ears to detect sound. Sound enters the ear, and travels along the auditory canal. travels along the auditory canal.

It then causes the tympanic membrane to vibrate at the same It then causes the tympanic membrane to vibrate at the same frequency as the sound waves. In the middle ear the ossicles frequency as the sound waves. In the middle ear the ossicles transfer and amplify the sound vibrations to the oval window. It then transfer and amplify the sound vibrations to the oval window. It then transfers the sound vibrations to the fluid-filled cochlea. transfers the sound vibrations to the fluid-filled cochlea.

Inside the cochlea is the organ of Corti, which has rows of hair cells Inside the cochlea is the organ of Corti, which has rows of hair cells that respond to different frequencies, convert vibrations into an that respond to different frequencies, convert vibrations into an electrochemical impulse and transfer the message to brain via the electrochemical impulse and transfer the message to brain via the auditory nerve.6auditory nerve.6

Anatomy and function of the Anatomy and function of the human earhuman ear

PinnaPinna Tympanic membraneTympanic membrane Ear ossiclesEar ossicles Oval windowOval window Round windowRound window CochleaCochlea Organ of CortiOrgan of Corti Auditory nerveAuditory nerve

Function of each part of the earFunction of each part of the earStructureStructure AnatomyAnatomy Function Function

PinnaPinna Freshly external organ Freshly external organ consisting of a flop of cartilage consisting of a flop of cartilage and skinand skin

Collects sound and directs into Collects sound and directs into the ear canalthe ear canal

Tympanic membrane (eardrum)Tympanic membrane (eardrum) Thin membrane between the Thin membrane between the external ear and the middle earexternal ear and the middle ear

Vibrates when sound waves Vibrates when sound waves reach it; transfers the vibration reach it; transfers the vibration to the hammerto the hammer

Ear ossiclesEar ossicles Three tiny bones located in the Three tiny bones located in the middle ear; hammer, anvil and middle ear; hammer, anvil and stirrupstirrup

Magnify and transfer vibrations Magnify and transfer vibrations from the tympanic membrane to from the tympanic membrane to the oval window on the cochleathe oval window on the cochlea

Oval windowOval window Flexible membrane between the Flexible membrane between the middle and inner earmiddle and inner ear

Transfers vibrations from the Transfers vibrations from the stirrup to the fluid in the cochleastirrup to the fluid in the cochlea

Round windowRound window Flexible membrane between the Flexible membrane between the middle and inner earmiddle and inner ear

Bulges outwards (into the Bulges outwards (into the middle ear) to allow middle ear) to allow displacement of fluid when displacement of fluid when vibrations are transferred to the vibrations are transferred to the cochleacochlea

CochleaCochlea Fluid-filled spiral tube that Fluid-filled spiral tube that contains the organ of Corticontains the organ of Corti

Detects different frequencies of Detects different frequencies of sound -high pitch sounds are sound -high pitch sounds are detected at the start of the detected at the start of the cochlea and low pitch sounds at cochlea and low pitch sounds at the end of the spiralthe end of the spiral

StructureStructure AnatomyAnatomy Function Function

Organ of CortiOrgan of Corti Consists of hair cells on the Consists of hair cells on the

basilar membranebasilar membrane Hair cells translate vibrations Hair cells translate vibrations

into electrochemical signalsinto electrochemical signals

Auditory nerveAuditory nerve Consists of the axons of the Consists of the axons of the hair cells and lead from the hair cells and lead from the

cochlea to the braincochlea to the brain

Transfers the impulse from hair Transfers the impulse from hair

cells to the braincells to the brain

Role of the Eustachian tubeRole of the Eustachian tube The Eustachian tube connects the middle ear with the back of the The Eustachian tube connects the middle ear with the back of the

throat. It is filled with air and responds to changes in pressure. The throat. It is filled with air and responds to changes in pressure. The role of the Eustachian tubes is to keep the pressure in the middle role of the Eustachian tubes is to keep the pressure in the middle ear and the throat and therefore the outside atmosphere equal and ear and the throat and therefore the outside atmosphere equal and to drain the middle ear. It also replaces the air in the middle ear after to drain the middle ear. It also replaces the air in the middle ear after it has been absorbed.it has been absorbed.

Path of sound wave through the external, Path of sound wave through the external,

middle and inner earmiddle and inner ear When sound waves enter the pinna they travel along the auditory When sound waves enter the pinna they travel along the auditory

canal and cause the tympanic membrane (eardrum) to vibrate. canal and cause the tympanic membrane (eardrum) to vibrate. These vibrations are carried and amplified by the ossicles in the These vibrations are carried and amplified by the ossicles in the middle ear. The ossicles are three tiny bones also known as the middle ear. The ossicles are three tiny bones also known as the malleus (hammer), the incus (the anvil) and the stapes (the stirrup). malleus (hammer), the incus (the anvil) and the stapes (the stirrup). The ossicles join the inner ear at the oval window. The ossicles join the inner ear at the oval window.

The cochlea is a snail-shaped, fluid-filled structure in the inner ear. The cochlea is a snail-shaped, fluid-filled structure in the inner ear. Inside the cochlea is another structure called the organ of Corti. Inside the cochlea is another structure called the organ of Corti. Inside the organ of Corti there are hair cells located on the basilar Inside the organ of Corti there are hair cells located on the basilar membrane. These are in contact with the tectorial membrane. When membrane. These are in contact with the tectorial membrane. When vibrations reach the hair cell the message is converted into an vibrations reach the hair cell the message is converted into an electrochemical response, which travels via the auditory nerve to electrochemical response, which travels via the auditory nerve to the brain.the brain.

Energy pathEnergy path

Relationship between the distribution of hair cells in Relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of the organ of Corti and the detection of sounds of

different frequenciesdifferent frequencies

Frequencies of sounds are detected in the organ of Frequencies of sounds are detected in the organ of Corti. This has three main components: the basilar Corti. This has three main components: the basilar membrane, hair cells and the tectorial membrane.membrane, hair cells and the tectorial membrane.

The basilar membrane is composed of transverse The basilar membrane is composed of transverse fibres of varying lengths. Vibrations received at the fibres of varying lengths. Vibrations received at the oval window are transmitted through the fluids of the oval window are transmitted through the fluids of the cochlea causing the transverse fibres of the cochlea causing the transverse fibres of the membrane to vibrate at certain places according to membrane to vibrate at certain places according to the frequency.the frequency.

Relationship between the distribution of hair cells in Relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of the organ of Corti and the detection of sounds of

different frequenciesdifferent frequencies

High frequency sounds cause the short fibres of the High frequency sounds cause the short fibres of the front part of the membrane to vibrate and low front part of the membrane to vibrate and low frequency sounds stimulate the longer fibres towards frequency sounds stimulate the longer fibres towards the far end.the far end.

As the basilar membrane vibrates, the hairs of the As the basilar membrane vibrates, the hairs of the hair cells are pushed against the tectorial membrane. hair cells are pushed against the tectorial membrane. This causes the hair cells to send an electrochemical This causes the hair cells to send an electrochemical impulse along the auditory nerve to the brainimpulse along the auditory nerve to the brain

Role of the sound shadow castRole of the sound shadow cast

Humans and other animals use two methods to locate Humans and other animals use two methods to locate the source of sound: the difference in time between the the source of sound: the difference in time between the sound arriving at each ear, and the difference in the sound arriving at each ear, and the difference in the intensity of the sound arriving at each ear. These intensity of the sound arriving at each ear. These differences occur because the head casts a sound differences occur because the head casts a sound shadow that causes one ear to receive less intense shadow that causes one ear to receive less intense sound than the other. sound than the other.

Humans usually trace the location of a sound by turning Humans usually trace the location of a sound by turning their heads until the intensity of the sound is equal in their heads until the intensity of the sound is equal in both ears; at this point people should be looking in the both ears; at this point people should be looking in the direction of the source of the sound. Other animals have direction of the source of the sound. Other animals have more mobile ears, rather than their heads, to pick up a more mobile ears, rather than their heads, to pick up a soundsound

Comparison of frequency rangeComparison of frequency range Humans can hear in the range 20 to 20000 Hz. Younger Humans can hear in the range 20 to 20000 Hz. Younger

children can hear frequencies up to 25000 Hz but this children can hear frequencies up to 25000 Hz but this ability decreases with age. Human hear best from about ability decreases with age. Human hear best from about 2000-4000 HZ because this is the range in which human 2000-4000 HZ because this is the range in which human speech falls. speech falls.

Bats produce sound in 2000 to 110000Hz range through Bats produce sound in 2000 to 110000Hz range through their mouths or through elaborate nose organs. The their mouths or through elaborate nose organs. The insect-catching bats use echolocation to locate their prey insect-catching bats use echolocation to locate their prey in mid air. To do this they send out high frequency sound in mid air. To do this they send out high frequency sound (ultrasonic) and then interpret the echo that bounces (ultrasonic) and then interpret the echo that bounces back. This gives them information on the distance and back. This gives them information on the distance and the direction of movement.the direction of movement.

Comparison of frequency rangeComparison of frequency range Dolphins belong to the toothed whales group, which have a very Dolphins belong to the toothed whales group, which have a very

high frequency hearing range between 75 to 150000 Hz. They have high frequency hearing range between 75 to 150000 Hz. They have specialized inner ears. They have more nerve endings than specialized inner ears. They have more nerve endings than terrestrial animals. Dolphins have adaptations for very high terrestrial animals. Dolphins have adaptations for very high frequency sound detection such as a thick basilar membrane and frequency sound detection such as a thick basilar membrane and bony supports for the cochlea.bony supports for the cochlea.

Sound becomes important in environments where visual information Sound becomes important in environments where visual information is limited. It plays an important role in finding mates, prey and is limited. It plays an important role in finding mates, prey and avoiding predators. Bats use sound to navigate in dark avoiding predators. Bats use sound to navigate in dark environments to avoid objects and to locate prey. They use high environments to avoid objects and to locate prey. They use high frequency sound, which is only useful over short distances. Dolphins frequency sound, which is only useful over short distances. Dolphins have high frequency hearing. High frequency sound is used over have high frequency hearing. High frequency sound is used over short distances to locate prey.short distances to locate prey.

Hearing aid (vs.) Cochlear Hearing aid (vs.) Cochlear implantimplant

Hearing AidHearing Aid Cochlear ImplantsCochlear Implants

PositionPosition ““In the ear” types are made of In the ear” types are made of moulded plastic and fit in to the moulded plastic and fit in to the outer ear (used for mild to severe outer ear (used for mild to severe

hearing loss).hearing loss).

Consists of internal and external Consists of internal and external parts. The internal parts are parts. The internal parts are placed surgically in the bone placed surgically in the bone behind the ear and the inner eat. behind the ear and the inner eat. The external parts can be The external parts can be detached at any time.detached at any time.

Type of energy Type of energy transfertransfer

Hearing aids receive sound Hearing aids receive sound through a microphone, which then through a microphone, which then converts the sound waves to converts the sound waves to electrical signals. The amplifier electrical signals. The amplifier increases the loudness of the increases the loudness of the signals and then sends the sound signals and then sends the sound to the ear through a speaker.to the ear through a speaker.

Sound is detected by a Sound is detected by a microphone. Transmits sound to microphone. Transmits sound to speech processor which codes speech processor which codes the sounds electronically and the sounds electronically and transmits them via a wire to the transmits them via a wire to the transmitting coil which sends the transmitting coil which sends the messages through the skin via messages through the skin via radio waves to the radio waves to the receiver/simulator which sends receiver/simulator which sends the sound as electrical signals the sound as electrical signals which stimulate particular nerves which stimulate particular nerves to send the messages to the to send the messages to the brain. brain.

Hearing AidHearing Aid Cochlear ImplantsCochlear Implants

Conditions Conditions under which under which they helpthey help

Patients that have residual Patients that have residual hearing loss. Hearing aids are hearing loss. Hearing aids are particularly useful for those particularly useful for those patients that have sensorineural patients that have sensorineural hearing loss (caused by aging, hearing loss (caused by aging, noise, illness etc). They aid in noise, illness etc). They aid in improving speech improving speech comprehension and general comprehension and general hearinghearing

Patients who are profoundly deaf Patients who are profoundly deaf but still have enough surviving but still have enough surviving auditory nerve fibres. Mostly auditory nerve fibres. Mostly used in young children (aged 2 used in young children (aged 2 and up) who will gain no and up) who will gain no advantage from the use of advantage from the use of hearing aidshearing aids

Limitations Limitations ““In the Ear” types can’t be used In the Ear” types can’t be used for children because they have to for children because they have to be remodeled to fit inside the ear be remodeled to fit inside the ear as the child grows so it isn’t as the child grows so it isn’t practical. They can also be practical. They can also be damaged by earwax and ear damaged by earwax and ear drainage. Hearing aids will not drainage. Hearing aids will not restore normal hearing or restore normal hearing or eliminate background noise. eliminate background noise. They can also be difficult to They can also be difficult to adjust to suit varying noise adjust to suit varying noise conditions. They are also battery conditions. They are also battery operated, so if the battery runs operated, so if the battery runs put they won’t work.put they won’t work.

The Cochlear implant does not The Cochlear implant does not fully reproduce the sounds hear fully reproduce the sounds hear by someone with normal hearing. by someone with normal hearing. It enables patients to have about It enables patients to have about 80% speech recognition. It is 80% speech recognition. It is also expensive around $60,000 also expensive around $60,000 for the surgery and the cochlear for the surgery and the cochlear implant.implant.