Sound For Class 9 Science Summary notes

Particles in Waves

Introduction to waves

A wave is a disturbance in a medium that moves from one point to another and carries energy without a net movement of particles. It may take the form of elastic deformation or a variation of pressure.

E.g: a Rubber cork on the water that goes up and down when a rock falls in the water creates a ripple

What is Wave-Particle Duality?

We have heard about the nature of light and the characters it displays. Interference, reflection, refraction, and diffraction are some of the characteristics. Wave-Particle Duality helps us to understand the particle and wave nature of light.

Based on the idea that light and all other electromagnetic radiation may be considered a particle or a wave nature, in 1923 physicists Louis De Broglie suggested that the same kind of duality must be applicable to the matter. He proposed that any particle of matter having momentum (p) Has an associated wavelength (λ).

De Broglie Wavelength formula is given by λ= h/p

Where h is the Planck constant

for a particle of momentum mv, the wavelength is given by λ=h/mv

This equation is also applicable for photons too.

Early in this century, De Broglie began to realize the extent to which both models describe the same phenomena. Waves can be described as particles; particles, as waves. Diffraction and interference phenomena reveal a wave-like character in light, but the photoelectric effect, absorption and emission by atoms show light to have a particle-like character as well. Electrons have mass but can be diffracted like caves. Nature reveals a particle duality and ambiguity uncharacteristic of science. While the meaning of this wave-particle duality remains a subject of intense debate, many physicists now accept the Bohr complement-yarn principle. The two models exclude one another, yet both are necessary for a complete description of nature. e.

According to Planck’s Hypothesis of the Quantum Theory, the energy is emitted in quanta, which are little packets of energy. He states that energy emitted is related to the frequency of the emitted light and this can be considered a Wave-Particle Duality definition. According to Planck’s hypothesis, the quantum energy is related to the frequency by the equation E = hν.

Observing a light is one of the easiest ways to prove the duality between a particle and a wave. Since light is similar to waves, it is able to diffract, refract, interface, etc.

Albert Einstein’s theory of photoelectric effect significantly contributed to De Broglie’s Theory and acted as proof that particles and waves could overlap. Light can also be observed in the form of a particle called a photon. When light is seen on certain objects, electrons are released. A certain amount of energy is needed to eliminate an electron from the surface of an object. So, when a photon of greater energy than an electron hits a solid, an electron will be emitted.

When the electrons are emitted, they also release kinetic energy. According to classical wave theory, the greater the intensity; the greater the energy. Because the energy of a wave is directly proportional to its amplitude, it was complex for scientists to find high-intensity lights that did not affect its overall kinetic energy.

Researchers discovered that light frequency effectively changed the amount of kinetic energy. Since some objects do not emit electrons at particular frequencies, a threshold value V₀ is applied. This threshold is used to describe the amount of kinetic energy required for a photon to eject an electron. The scientists arrived at a linear relationship between frequency and kinetic energy which can be shown by the rough sketch below.

 

The slope of this line is known as Planck’s Constant, h = 6.63 x 10^-34

Since the energy of waves and the energy of light do not coincide, we can say that light is a particle that has the property of waves.

Particle motion of mechanical waves

(i) Transverse Waves

Particle motion is perpendicular to the direction of wave motion.  This type of wave is a mechanical wave.

E.g: Light and Mexican wave in a stadium.

(ii) Longitudinal waves

Particles travel parallel to the direction of wave motion, by means of successive compressions or elongations. This is also a mechanical wave.

E.g: Sound waves in the air.

What are Waves?

A wave transmits information or energy from one point to another in the form of signals, but no material object makes this journey. The frequency of a wave is obtained by including a factor of time in the mix. We are completely dependent on waves for all of our wireless communications.

For example, if you make a call to your friend in another city with your mobile phone, the entire communication is happening via audio, but the entire process of transmission of a signal from the talker to the receiver occurs as a waveform. The phone converts your voice into an electrical signal which then propagates either through copper wires or through antennae in wireless communication.

A wave is a flow or transfer of energy in the form of oscillation through a medium – space or mass. Sea waves or tides, a sound we hear, a photon of light traveling, and even the movement of small plants blown by the wind are all examples of different waves. A simple wave illustration is as follows.

Types of Waves in Physics

Different types of waves have different sets of characteristics. Based on the orientation of particle motion and direction of energy, there are three categories:

• Mechanical waves
• Electromagnetic waves
• Matter waves

Mechanical Wave

• A mechanical wave is a wave that is an oscillation of matter and is responsible for the transfer of energy through a medium.
• The distance of the wave’s propagation is limited by the medium of transmission. In this case, the oscillating material moves about a fixed point, and there is very little translational motion. One intriguing property of mechanical waves is the way they are measured, which is given by displacement divided by the wavelength. When this dimensionless factor is 1, it generates harmonic effects; for example, waves break on the beach when this factor exceeds 1, resulting in turbulence.

There are two types of mechanical waves:

• Longitudinal waves – In this type of wave, the movement of the particles is parallel to the motion of the energy, i.e. the displacement of the medium is in the same direction in which the wave is moving. Example – Sound Waves, Pressure Waves.
• Transverse waves –  When the movement of the particles is at right angles or perpendicular to the motion of the energy, then this type of wave is known as a transverse wave.  Light is an example of a transverse wave.

Water waves are an example of a combination of both longitudinal and transverse motions.

• Surface waves – In this type, the particles travel in a circular motion.  These waves usually occur at interfaces. Waves in the ocean and ripples in a cup of water are examples of such waves.

Electromagnetic Wave

• Electromagnetic waves are created by a fusion of electric and magnetic fields. The light you see, and the colors around you are visible because of electromagnetic waves.
• One interesting property here is that, unlike mechanical waves, electromagnetic waves do not need a medium to travel. All electromagnetic waves travel through a vacuum at the same speed, 299,792,458 ms^-1.

Following are the different types of electromagnetic waves:

• Microwaves
• X-ray
• Radio waves
• Ultraviolet waves

Learn more about Sound waves here.

Difference Between Mechanical Wave and Non-Mechanical Wave

Mechanical Waves vs Non-Mechanical Waves
Mechanical Wave	Non-Mechanical Wave
Mechanical waves are waves that need a medium for propagation.	Non-mechanical waves are waves that do not need any medium for propagation.
Sound waves, water waves, and seismic waves are some examples of mechanical waves.	The electromagnetic wave is the only non-mechanical wave.
Mechanical waves cannot travel through a vacuum	Non-mechanical waves can travel through a vacuum

Matter Wave

• This concept is a little complicated to understand. The dual nature of matter; its ability to exist both as a particle and a wave was first brought to light by the founders of the field of Quantum Physics.
• For example, a beam of electrons can be diffracted just like any other beam of electromagnetic radiation or water wave. This property of matter was brought forward by Louis de Broglie’s Hypothesis.

Sound Properties

Introduction to sound waves

Sound needs a medium to propagate. The matter or material through which sound propagates is called a medium. When particles vibrate about their mean positions, it pushes a region of compressed air, creating a region of high pressure, followed by a region of low pressure as the particle retreats to its mean position. The sound wave propagates by compressions and rarefactions of particles in a medium. Sound propagation can be visualized as the propagation of pressure variations in the medium.

Wavelength

The distance between two successive crests or troughs (or) successive compressions and rarefactions is called wavelength (λ).  The SI unit of wavelength is a meter (m).

Time period

Time taken by two consecutive compressions or rarefactions to cross a fixed point is called a Time period (T). The SI unit of time in seconds (s).

Frequency

The number of compressions or rarefactions per unit time is called frequency (𝛎).
The SI unit of frequency is Hertz. The  SI unit is Hertz (s−1)

Speed (v), wavelength (λ), and frequency (𝛎) are related as v=λ𝛎

Amplitude

The magnitude of disturbance in a medium on either side of the mean value is called an amplitude (A).
As shown in the figure below, the unit of amplitude will be the density or pressure. Distance between mean position and crest (maximum displacement).

Pitch

The number of compressions or rarefactions per unit time. Directly proportional to frequency.

Representation of low and high pitch

Volume

The volume or loudness of a sound depends on the amplitude. The force with which an object is made to vibrate gives the loudness.

Higher force → higher amplitude → louder sound

The amount of sound energy flowing per unit time through a unit area is called the intensity of sound.

                                                             The Intensity of Sound

Note and Tone

A sound of a single frequency is called a tone. A sound produced with a mixture of several frequencies is called a note.

Quality of sound

The richness or timber of sound is called quality. Sound with the same pitch and loudness can be distinguished based on the quality. Music is pleasant to the ears while noise is not. But they both can have the same loudness and pitch.

Speed of sound

Sound travels through different media at different speeds. The speed of sound depends on the properties of the medium: pressure, density, and temperature

Speed of sound: Solids > Liquids > Gases

Speed of sound in air = 331 m/s at 0⁰C and 344 m/s at 22^∘ C

When a source emits sound with a speed greater than the speed of sound in air, it creates a sonic boom that produces shockwaves with lots of energy. They produce a very loud noise which is enough to shatter glass and damage buildings.

Property of Sound

Sound is a vibration that travels through the medium in the form of longitudinal waves. This means that sound waves are waves in which the particles of the medium vibrate parallel to the direction of wave propagation. Sound waves are called mechanical waves since they require a medium to propagate. The medium can be solids, liquids, or gases. 5 Important Properties of Sound

Property 1: Pitch/Frequency

The perception of the frequency of sound by the human ear within the range of human hearing is called the pitch. The higher the frequency of the sound the higher is its pitch and a lower frequency mean a lower pitch. Frequency is the number of periodic compression and rarefaction cycles that occurs each second as the wave propagates through the medium.

Property 2: Amplitude/Loudness

The amplitude of the sound waves determines their loudness. The amplitude of the sound is a measure of the magnitude of the maximum disturbance of sound. The amplitude is also a measure of the energy of vibration. More energetic vibration causes a larger amplitude.

Property 3: Speed

The speed at which the sound waves travel through the medium is called the speed of sound. The speed of sound is different for different mediums. Sound travels fastest in solids since the atoms in a solid are closely packed.

Property 4: Reflection of sound

When sound waves hit the surface of a solid or light, it bounces back to the same medium. This is called the reflection of sound. Sound waves, like light waves, follow the laws of reflection.

Property 5: Timbre

Timbre is the property used to differentiate sounds of the same frequency. Timbre depends on the material through which the sound is produced.

Echo

The phenomenon where a sound produced is heard again due to reflection is called an echo.
E.g: Clapping or shouting near a tall building or a mountain.

To hear a distinct echo sound, the time interval between original and reflected sound must be at least 0.1s. As sound persists in our brain for about 0.1s. The minimum distance for obstruction or reflective surface to hear an echo should be 17.2 m. Multiple echoes can be heard due to multiple reflections.

Reflection of Sound and its Application

The concept of reflection of sound is familiar to everyone. Let’s understand this through a small activity. If we take two tubes and position them against a wall, as shown in the figure below, upon placing a speaker or any other source of sound near one end of the tube, we receive the sound at the end of the other tube. This activity proves that the surface of the wall reflects the sound wave. In this section, we shall learn more about the reflection of sound and its application in day-to-day life.

Sound: Definition

Sound is defined as oscillations or auditory sensations evoked by oscillations in particle displacement or velocity, propagated in a medium with internal force. Sound propagates as a mechanical wave, through a medium such as air or water.

Reflections of sound

Just like the reflection of light, the reflection of sound is similar as it follows the laws of reflections, where the angle of reflection is equal to the angle of incidence and the reflected sound, the incident sound, and the normal sound belong in the same plane. Sound bounces off the surface of the medium which can be a solid or a liquid. In order to make the reflection of sound to occur, the surface can be of large size and can be either rough or polished.

Laws of Reflection of Sound

• The angle of reflection is always equal to the angle of incidence.
• The reflected sound, the incident sound, and the normal sound belong in the same plane.

Applications of reflection of sound

Echo:

The sound heard after reflections from a rigid surface such as a cliff or a wall is called echo creating a persistence of sound even after the source of sound has stopped vibrating. The echo is used by bats and dolphins to detect obstacles or to navigate. The same principle is used in SONAR (Sound Navigation And Ranging technique), used in oceanographic studies. SONAR is used for the detection and location of unseen underwater objects, such as submerged submarines, sunken ships, and icebergs. In SONAR, ultrasonic waves are sent in all directions from the ship and the received signal is analyzed.

Hearing aid:

A hearing aid is a device used by people with difficulty in hearing. Here, the sound waves are received by the hearing aid and are reflected in a narrower area leading to the ear.

Megaphone:

Megaphones are horn-shaped tubes that prevent the spreading out of sound waves by successive reflections, thus confining them to the air in the tube.

Soundboard:

Soundboards are curved surfaces that are placed in such a way that the sound source is at the focus. The sound waves are made to reflect equally throughout the hall or an auditorium thus enhancing their quality.

Uses of Radar

We know that one of the core uses of Radar is to send and receive valuable information in the form of waves. RADAR is helpful in detecting incoming signals during the war and is also used by a geologist for earthquake detection. Archaeologists use this technology for the detection of buried artifacts. It is also used to understand the environment and climatic changes.

Applications and uses of Radar are given below:

• Military
• Law enforcement
• Space
• Remote sensing of the environment
• Aircraft navigation
• Ship Navigation
• Air Traffic Controller

RADAR is used in the Military

Radars have a wide range of usage in military operations. They are used for Naval, Ground as well as Air defense purposes. They are used for detection, tracking, and surveillance purposes also. Weapon control and missile guidance often use various types of RADARs.

These are used in Law Enforcement

Law enforcement, especially highway police, has extensive use of RADARs during a pursuit to measure the speed of a vehicle. Due to bad weather conditions, when the satellite cannot get a clear image of traffic and barricades, RADARs are used to get the desired results.

This technology is used in Space

RADARs in satellites are used for remote sensing. RADARs are used to track and detect satellites and spacecraft. They are also used for safely landing and docking spacecraft.

RADAR is used for Remote Sensing of the Environment

Just like various types of waves are received by an antenna. This technology is also used to detect whether conditions of the atmosphere. It is also used for tracking the motions of planets, asteroids and other celestial bodies in the solar system.

It is used in Aircraft Navigation

Ground mapping and weather avoidance RADARs are used in aircraft to navigate them properly. This technology enables an aircraft to ensure the location of obstacles that can threaten the flight plan.

Uses of RADAR in Navigating Ships

Ships are guided through high resolutions RADARs situated on the shores. Because of poor visibility in bad weather conditions, RADARs provide safety by warning threats. These ships often use this technology to measure the proximity of other ships and their speed on the water.

RADARs are used in Air Traffic Controller

RADARs are used to safely control air traffic. It is used to guide aircraft for proper landing and take-off during bad weather conditions. These RADARs also detect the proximity and the altitude of the aircraft.

Sonar and Radar

SONAR – Sound Navigation And Ranging.

It is a technique that uses sound or ultrasonic waves to measure distance. The human range of hearing is 20Hz- 20kHz.

What are Ultrasonic sounds?

Ultrasonic sounds are high-frequency sounds having a frequency greater than 20kHz (inaudible range).

Applications of Ultrasound

(i) Scanning images of human organs
(ii) Detecting cracks in metal blocks
(iii) Cleaning parts that are hard to reach
(iv) Navigating, communicating, or detecting objects on or under the surface of the water (SONAR).

Sonar consists of a transmitter and detector mounted on a boat or ship. The transmitter sends ultrasonic sound waves to the seabed which get reflected back and picked up by the detector. Knowing the speed of sound in water, distance can be measured using:   2d=v×t. This method is called echo-location or echo ranging.

Reverberation

The persistence of sound because of multiple reflections is called reverberation. Examples: Auditorium and a big hall.
Excessive reverberation is undesirable and to reduce this, halls and auditoriums have sound-absorbing materials on the walls and roofs.  E.g: Fibreboard and rough plaster. 

Reverberation: Definition

Reverberation is the phenomenon of persistence of sound after it has been stopped as a result of multiple reflections from surfaces such as furniture, people, air, etc. within a closed surface. These reflections build up with each reflection and decay gradually as they are absorbed by the surfaces of objects in the space enclosed.

It is the same as the echo, but the distance between the source of the sound and also the obstacle through which it gets reflected is less in the case of this reverberation. The quantitative characterization of the reverberation is mainly done by using the parameter called reverberation time. Reverberation time is usually defined as the length of the time when the sound decays by about 60 decibels starting from the initial level. In the process of reverberation, the time delay is said to be not less than 0.1 seconds i.e. the reflected form of the wave reaches the observer in more or less than 0.1 seconds. Hence, this delay in the perception of the sound and also the original sound is said to be very less and whereas the original sound will be still in the memory when this reflected sound is heard.

Advantages of Reverberation

Reverberations do wonders when it comes to musical symphonies and orchestra halls, when the right amount of reverberation is present, the sound quality gets enhanced drastically. This is the reason why sound engineers are appointed during the construction of these halls.

Disadvantages of Reverberation

If a room has about nearly no sound-absorbing surfaces like wall, roof, and the floor, the sound is said to bounce back between the surfaces, and also it takes a very long time as the sound dies. In such a room, the listener will then have a problem with registering the speaker. This is because he tends to hear both the direct sound and the repeated reflected sound waves. And also if these reverberations will be more excessive, the sound is said to run together with a mere loss of articulation, and it becomes muddy and also garbled.

Application of reverberation

The phenomenon of reverberation is utilized by the producers of living or recorded music in order to enhance sound quality. Several systems have been developed to produce and simulate reverberations. A Chamber reverberator is one such example, where the sound is produced by a loudspeaker which is then picked by a microphone along with other effects of the reverb. A similar device is a plate reverberator, where a metal plate is used to produce vibrations instead of a loudspeaker.

How can we reduce reverberations?

From our observation, we can say that, if the surface of the objects in the nearby enclosed space is covered with sound-absorbing material, the reflected sound will decay much quicker and the listener will thus receive only the original sound. Porous materials such as mineral wool and fiberglass are examples of such absorbents. As the sound waves penetrate mineral wool, sound energy gets converted to heat through friction.

Doppler’s effect

If either the source of sound or the observer is moving, then there will be a change in frequency and wavelength for the observer. The frequency will be higher when the observer moves towards the source and it decreases when the observer moves away from the source.

Example: If one is standing on a street corner and an ambulance approaches with its siren blaring, the sound of the siren steadily gains in pitch as it comes closer, and then, as it passes, the pitch suddenly lowers.

Doppler Effect Explained

Doppler effect is an important phenomenon in various scientific disciplines, including planetary science. The Doppler effect or the Doppler shift describes the changes in the frequency of any sound or light wave produced by a moving source with respect to an observer.

Doppler effect in physics is defined as the increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other.

Waves emitted by a source traveling towards an observer get compressed. In contrast, waves emitted by a source traveling away from an observer get stretched out. Christian Johann Doppler first proposed the Doppler Effect (Doppler Shift) in 1842.

Doppler Effect Examples

Let us imagine the following scenario:

Case 1: Two people A and B, are standing on the road, as shown below in the picture.

Which person hears the sound of the revving engine with a greater magnitude?

Person A hears the sound of the revving engine with a greater magnitude than person B. Person B, standing behind the car, receives fewer waves per second (because they’re spread out), resulting in a low-pitched sound. But, person A who is in front of the car, receives more of those soundwave ripples per second. As a result, the frequency of the waves is higher, which means the sound has a higher pitch.

Case 2: Now let us consider the following situations:

Situation 1: How is the pattern of waves formed when you suddenly jump into a pond?
Situation 2: How is the pattern of waves formed when you are walking in a pond?

The image given below highlights the difference between wave patterns in both situations.

The difference in the wave pattern is due to the source’s movement in the second case. This is what the Doppler effect is. In the Doppler effect, the frequency received by the observer is higher during the approach, identical when the relative positions are the same, and keeps lowering on the recession of the source.

In this video let’s see how relative motion between the source and the observer changes the frequency of sound waves giving rise to the Doppler Effect.

Doppler Effect Formula

Doppler effect is the apparent change in the frequency of waves due to the relative motion between the source of the sound and the observer. We can deduce the apparent frequency in the Doppler effect using the following equation:

While there is only one Doppler effect equation, the above equation changes in different situations depending on the velocities of the observer or the source of the sound. Let us see below how we can use the equation of the Doppler effect in different situations.

(a) Source Moving Towards the Observer at Rest

In this case, the observer’s velocity is zero, so V₀ is equal to zero. Substituting this into the Doppler effect equation above, we get the equation of the Doppler effect when a source is moving towards an observer at rest as:

(b) Source Moving Away from the Observer at Rest

Since the velocity of the observer is zero, we can eliminate V₀ from the equation. But this time, the source moves away from the observer, so its velocity is negative to indicate the direction. Hence, the equation now becomes as follows:

(c) Observer Moving Towards a Stationary Source

In this case, v_s will equal zero, hence we get the following equation:

(d)Observer Moving Away from a Stationary Source

Since the observer is moving away, the velocity of the observer becomes negative. So, instead of adding V₀, we now subtract, since V₀ is negative.

Uses of Doppler Effect

Many people mistake the Doppler effect to be applicable only for sound waves. It works with all types of waves including light. Below, we have listed a few applications of the doppler effect:

• Sirens
• Radar
• Astronomy
• Medical Imaging
• Blood Flow Measurement
• Satellite Communication
• Vibration Measurement
• Developmental Biology
• Audio
• Velocity Profile Measurement

Doppler Effect Limitations

• Doppler Effect is applicable only when the velocities of the source of the sound and the observer are much less than the velocity of sound.
• The motion of both source and the observer should be along the same straight line.

Doppler Effect In Light

Doppler effect of light can be described as the apparent change in the frequency of the light observed by the observer due to relative motion between the source of light and the observer.
For sound waves, however, the equations for the Doppler shift differ markedly depending on whether it is the source, the observer, or the air, which is moving. Light requires no medium, and the Doppler shift for light traveling in a vacuum depends only on the relative speed of the observer and source.

Red Shift and Blue Shift

• When the light source moves away from the observer, the frequency received by the observer will be less than the frequency transmitted by the source. This causes a shift towards the red end of the visible light spectrum. Astronomers call it the redshift.
• When the light source moves towards the observer, the frequency received by the observer will be greater than the frequency transmitted by the source. This causes a shift towards the high-frequency end of the visible light spectrum. Astronomers call it the blue shift.

Human Ear

The ear is a sensitive organ of the human body. It is mainly involved with detecting, transmitting, and transducing sound, and maintaining a sense of balance is another important function of the human ear. The human ear includes:

• The outer ear or the visible part of the ear is called the pinna.
• Pinna collects sound from the surroundings.
• Sound passes through a tube called an auditory canal.
• The eardrum (tympanic membrane) vibrates in response to incident sound waves.
• Vibrations are amplified and transmitted further by three bones hammer, anvil, and stirrup in the middle ear to the inner ear.
• In the inner ear, the cochlea converts pressure signals into electrical signals.
• Electrical signals are transmitted by the auditory nerve to the brain for interpretation.

 

Structure of Ear

The human ear consists of three parts:

• External ear
• Middle ear
• Internal ear

Human Ear Parts

The human ear parts are explained below:

External Ear

The external ear is further divided into the following parts:

Auricle (Pinna)

The auricle comprises a thin plate of elastic cartilage covered by a layer of skin. It consists of funnel-like curves that collect sound waves and transmits them to the middle ear. The lobule consists of adipose and fibrous tissues supplied with blood capillaries.

External Auditory Meatus

It is a slightly curved canal supported by bone in its interior part and cartilage in the exterior part. The meatus or the canal is lined with stratified epithelium and wax glands.

Tympanic Membrane

This membrane separates the middle ear and the external ear. This part receives and amplifies the sound waves. Its central part is known as the umbo.

Middle Ear

The middle ear comprises the following parts:

Tympanic Cavity

It is a narrow air-filled cavity separated from the external ear by tympanic membrane and from inner ear by the bony wall. The tympanic cavity has an auditory tube known as the eustachian tube in its anterior wall.

Eustachian Tube

The eustachian tube is a 4cm long tube that equalizes air pressure on either side of the tympanic membrane. It connects the tympanic cavity with the nasopharynx.

Ear Ossicles

These are responsible for transmitting sound waves from the eardrum to the middle ear. There are three ear ossicles in the human ear:

• Malleus: A hammer-shaped part that is attached to the tympanic membrane through the handle and incus through the head. It is the largest ear ossicle.
• Incus: An anvil-shaped ear ossicle connected with the stapes.
• Stapes: It is the smallest ossicle and also the smallest bone in the human body.

Inner Ear

It comprises two parts:

• Bony labyrinth
• Membranous labyrinth

Bony Labyrinth

The bony labyrinth comprises a vestibule, three semi-circular canals, and a spirally coiled cochlea. It is filled with perilymph.

Membranous labyrinth

The bony labyrinth surrounds the membranous labyrinth. It comprises sensory receptors responsible for balance and hearing. The membranous labyrinth is filled with endolymph and comprises three semi-circular ducts, cochlear duct, saccule, and utricle. The sensory receptors include cristae, an organ of Corti, and ampullar maculae.

Function of Ear

Following are the important function of the ear:

Hearing

The mechanism of hearing involves the following steps:

• The sound waves pass through the auditory canal and reach the eardrum.
• The vibrations produced pass through the tympanic membrane to the tympanic cavity.
• The ear ossicles in the tympanic cavity receive the vibrations and the stapes push the oval window in and out.
• This action is passed on to the organ of Corti, the receptor of hearing, which contains tiny hair cells that translate the vibrations into an electrical impulse that is transmitted to the brain by sensory nerves.

Balance

The eustachian tube and the vestibular complex are the important parts of the ear responsible for the balance.

• The eustachian tube equalizes the air pressure in the middle ear and maintains the balance.
• The vestibular complex contains receptors that maintain body balance.

Also Read: Anatomy and Physiology

For more information on the human ear, the structure of ear class 9, human ear parts, the function of the ear, and other related topics keep visiting BYJU’S website or download BYJU’S app for further reference.