Ans. Sound is a form of energy that produces the sensation of hearing in our ears. It helps us to communicate and know what is happening around us.

Sound is produced when an object vibrates. The vibrating object causes the particles of the surrounding medium (air, water, etc.) to vibrate. These vibrations travel in the form of sound waves and reach our ears, where we hear the sound.

Examples from daily life:

• Ringing bell: When we strike a school bell, its metal body starts vibrating. These vibrations produce sound waves which travel through the air and reach our ears as a ringing sound.
• Guitar or sitar: When the strings of a guitar or sitar are plucked, they begin to vibrate rapidly. These vibrating strings set the surrounding air into vibration and musical sound is produced.
• Human voice: When we speak, air from our lungs passes through the voice box and makes the vocal cords vibrate. The vibrations of the vocal cords produce sound which we hear as speech or song.

In all these cases, vibration of an object is necessary for the production of sound.

Ans. We can perform a simple activity using a metal ruler or scale to show that vibrating objects produce sound.

Step-wise activity:

• Take a metal or plastic ruler and fix one end of it firmly on the edge of a table using your hand or some heavy books, leaving the other end free outside the table.
• Pull the free end of the ruler slightly downwards and then release it. The ruler will start moving up and down rapidly, that is, it will vibrate.
• While it is vibrating, you will hear a buzzing sound coming from the vibrating ruler.
• After some time, the ruler slows down and finally comes to rest. At that moment, the sound also stops.

Observation: Sound is heard only when the ruler is vibrating. When the ruler stops vibrating, sound is no longer heard.

Conclusion: This activity shows that sound is produced by vibrating objects and when the vibrations stop, the sound also stops.

Ans. The vocal cords are two stretched, fold-like structures present in the voice box or larynx in our throat. There is a narrow gap between the cords through which air passes when we breathe out.

Production of sound:

• When we speak, air from the lungs is forced out through the narrow gap between the vocal cords.
• This air makes the vocal cords vibrate rapidly.
• The vibrating vocal cords cause the air around them to vibrate and sound is produced.
• This sound then gets modified by our tongue, teeth and lips to form different words and speech sounds.

Different sounds (pitch and loudness):

• Pitch: By tightening or loosening the vocal cords, we change the frequency of vibration and thus the pitch of our voice. Tight cords vibrate faster and produce a higher pitch (shrill sound), while loose cords vibrate slowly and produce a lower pitch (deep sound).
• Loudness: When more air is forced out from the lungs, the vocal cords vibrate with larger amplitude, producing a louder sound. If less air is pushed out, the amplitude is smaller and a soft sound is produced.

Therefore, by controlling the tension in the vocal cords and the force of air, human beings can produce various types of sounds while speaking or singing.

Ans. Sound travels through a medium in the form of waves.

Propagation of sound through air:

• When an object vibrates, it pushes the air particles near it closer together, creating a region of high pressure and high density called a compression.
• When the object moves back, the air particles spread out, creating a region of low pressure and low density called a rarefaction.
• These compressions and rarefactions follow one another and move forward through the air as longitudinal sound waves.
• When this series of compressions and rarefactions reaches our ears, it makes our eardrum vibrate. Our ear and brain then interpret these vibrations as sound.

Need for a medium:

• In sound waves, energy is passed on by the vibration of particles of the medium.
• If there are no particles, as in vacuum, there is nothing to vibrate and carry the energy.
• Therefore, sound cannot travel through vacuum and requires a material medium such as air, water or solids for its propagation.

Thus, sound reaches the listener only when there is a medium between the source and the ear to transfer the vibrations.

Ans. We can use an electric bell in a glass jar connected to a vacuum pump to show that sound needs a medium.

Apparatus: Electric bell with battery, glass bell jar, vacuum pump, switch, connecting wires.

Procedure:

• Fix an electric bell inside a glass bell jar and connect it to a battery and switch outside the jar.
• Initially, the jar is filled with air. Switch on the bell. You will hear the ringing sound clearly because the sound travels through the air in the jar.
• Now connect the jar to a vacuum pump and start removing the air slowly from the jar while the bell is still ringing.
• As more and more air is removed, the sound becomes weaker and fainter, even though the bell continues to vibrate.
• When most of the air has been removed (near vacuum), we can hardly hear the sound.

Observation: The loudness of sound decreases as the air is removed and almost disappears when there is no air.

Conclusion: Since sound becomes inaudible in vacuum even when the bell is still vibrating, it shows that sound cannot travel through vacuum and needs a material medium like air.

Ans. The speed of sound is not the same in all media. It is:

• Maximum in solids,
• Less in liquids, and
• Least in gases like air.

Reason: The speed of sound depends on how closely the particles of the medium are packed and how quickly they can pass on vibrations to each other.

• In solids, particles are very close together and strongly bonded. When one particle vibrates, it quickly passes the vibration to the next particle. So, sound travels fastest in solids.
• In liquids, particles are less tightly packed than in solids but closer than in gases. So, the speed of sound in liquids is less than solids but more than gases.
• In gases, particles are far apart. It takes more time for vibrations to pass from one particle to another. Hence, the speed of sound is lowest in gases.

Examples:

• If you keep your ear on a railway track, you can hear an approaching train through the metal track much earlier than hearing it through air.
• Underwater divers can hear sounds in water clearly because sound travels faster and better in water than in air.

Thus, the speed of sound is greatest in solids, then in liquids, and least in gases because of the different arrangements of particles in these media.

Ans. The two important characteristics of sound that we often notice are loudness and pitch.

Loudness and amplitude:

• Loudness tells us whether a sound is strong (loud) or weak (soft).
• It depends on the amplitude of vibration of the sound-producing body.
• If the amplitude is large, the sound produced is loud because more energy is carried by the sound wave.
• If the amplitude is small, the sound is soft because less energy is carried.
• Example: Hitting a drum hard makes its surface vibrate with large amplitude, producing a loud sound. Hitting it gently produces a soft sound.

Pitch and frequency:

• Pitch tells us whether a sound is shrill (high) or deep (low).
• It depends on the frequency of vibration of the sound-producing body.
• Higher frequency → higher pitch and shriller sound.
• Lower frequency → lower pitch and deeper sound.
• Example: A whistle or a child’s voice has a high frequency and thus a high pitch; a drum beat or an adult man’s voice has a lower frequency and therefore a lower pitch.

Thus, amplitude controls the loudness, and frequency controls the pitch of a sound, and both together give us the overall feel of the sound we hear.

Ans. Quality or timbre of sound is that characteristic which helps us to distinguish between sounds of the same pitch and loudness produced by different sources.

Explanation:

• Two sounds can have the same frequency (pitch) and amplitude (loudness) but still feel different to our ears.
• This difference is due to the different wave patterns produced by different musical instruments or voices.
• These different patterns arise because each instrument or voice produces a mixture of many frequencies along with the main frequency.

Examples:

• If a flute and a violin play the same musical note at the same loudness, we can still easily say which sound is from the flute and which is from the violin. This is due to the difference in quality of their sounds.
• Similarly, we can recognise the voice of our family members even if they speak at the same pitch and loudness, because every person has a unique quality of sound.

Thus, quality or timbre helps our ears and brain to identify and recognise the source of sound, even when pitch and loudness are similar.

Ans.

Frequency: Frequency is the number of complete vibrations or oscillations made by a vibrating body in one second. It is measured in hertz (Hz).

Time period: Time period is the time taken by a vibrating body to complete one full vibration. It is measured in seconds.

Relationship between frequency and time period:

• If a body makes n vibrations in t seconds, then:
  • Frequency \( f = \dfrac{n}{t} \)
  • Time period \( T = \dfrac{t}{n} \)
• For one second, \( t = 1 \) s, so we have:
  • \( f = \dfrac{1}{T} \)
  • \( T = \dfrac{1}{f} \)

Example: Suppose a tuning fork completes 100 vibrations in 2 seconds.

• Frequency \( f = \dfrac{100}{2} = 50 \) Hz.
• Time period \( T = \dfrac{1}{f} = \dfrac{1}{50} \) second.

Thus, frequency and time period are inversely related: if frequency is high, time period is small, and if frequency is low, time period is large.

Ans. The audible range of a normal human ear is roughly from 20 Hz to 20,000 Hz. Sounds within this frequency range can usually be heard by humans.

Infrasonic sounds:

• Sounds having frequency lower than 20 Hz are called infrasonic sounds.
• Humans cannot hear them because their frequency is below the audible range.
• Some animals, such as elephants, are believed to produce and hear infrasonic sounds for communication over long distances.

Ultrasonic sounds:

• Sounds having frequency higher than 20,000 Hz are called ultrasonic sounds.
• Humans cannot hear these sounds because their frequency is above the audible range.
• Some animals, such as bats and dolphins, can hear ultrasonic sounds. Bats use ultrasonic waves to detect obstacles and locate insects even in the dark. This process is called echolocation.

Thus, while humans can hear only sounds in a limited frequency range, many animals can hear sounds beyond our range.

Ans. Ultrasonic waves, although not audible to humans, are very useful in many fields.

Some important applications are:

• Medical ultrasound scanning: Doctors use ultrasonic waves to get images of internal organs such as liver, kidney and heart. They are also used to observe the growth and position of a baby in the mother’s womb. This helps in diagnosis without surgery, so it is safe and painless.
• Cleaning delicate objects: Ultrasonic cleaners are used to clean small and delicate parts such as jewellery, lenses and machine parts. The objects are placed in a liquid, and ultrasonic waves are passed through it. Tiny bubbles formed by these waves remove dirt from even very small corners.
• Industrial use and flaw detection: Ultrasonic waves are used to find cracks and defects in metal parts, railway tracks and bridges. The waves are sent into the object and the reflected waves are studied. If there is a crack, the pattern of reflection changes, indicating a defect.

Thus, ultrasonic waves are very useful in medicine, industry and many other areas because of their high frequency and ability to travel in narrow beams.

Ans. Musical sound and noise are two different types of sounds.

Differences:

• Nature of sound:
  • Musical sound: Pleasant to hear and soothing.
  • Noise: Unpleasant and irritating to hear.
• Wave pattern:
  • Musical sound: Has a regular, repeating pattern of vibrations.
  • Noise: Has an irregular and random pattern of vibrations.
• Effect on mind and health:
  • Musical sound: Usually makes us feel relaxed and happy.
  • Noise: Causes disturbance, headache and lack of concentration.
• Examples:
  • Musical sound: Sound produced by a piano, flute, harmonium or a well-tuned orchestra.
  • Noise: Sound of traffic jam, bursting of crackers, loud shouting or running machines.

Thus, while musical sound is desirable and pleasant, noise is unwanted and can even cause health problems if it is very loud for a long time.

Ans. Noise pollution is the presence of excessive or unwanted sound in the environment.

Main causes of noise pollution:

• Road traffic: Continuous movement of vehicles, unnecessary honking and use of loud horns on busy roads create high levels of noise.
• Industrial activities: Factories, mills and construction sites use heavy machines, drills and equipment which produce loud sound while working.
• Loudspeakers and music systems: Use of loudspeakers during weddings, functions, religious gatherings and political rallies, often at high volume, contributes to noise pollution.
• Household appliances: Mixers, grinders, vacuum cleaners, televisions and music systems can also add to noise if used carelessly at high volume.
• Crackers: Bursting of firecrackers during festivals and celebrations suddenly increases the noise level in both cities and villages.

Effects of noise pollution on human health:

• It causes headache, stress and irritability.
• It disturbs sleep, leading to tiredness and lack of rest.
• It affects concentration, especially in students, and reduces work efficiency.
• Long-term exposure to loud noise can cause partial or permanent hearing loss.
• It may also lead to high blood pressure and other health problems in sensitive people.

Therefore, it is very important to control noise pollution to protect our physical and mental health.

Ans. Noise pollution can be controlled only when individuals, society and the government work together.

Measures at individual level:

• Avoid using horns unnecessarily while driving and use them only when needed for safety.
• Keep the volume of television, music systems and mobile phones low, especially at night.
• Avoid bursting loud firecrackers and encourage others to use silent or fewer crackers.

Measures at community level:

• Use loudspeakers at a controlled volume and only for limited hours; follow time limits fixed by local authorities.
• Plant trees along roadsides and around buildings because trees act as natural sound barriers.
• Develop “silence zones” around schools, hospitals and libraries where loud noise is not allowed.

Measures at government level:

• Frame and strictly implement laws to control the use of loudspeakers and high-volume music.
• Set permissible limits for noise levels in residential, commercial and industrial areas.
• Ensure that industries use silencers and sound-proofing and are set up away from residential areas.

By following these measures, noise pollution can be reduced and a healthier environment can be created for everyone.

Ans. (Students should draw the diagram in their notebook as per NCERT textbook.)

The human ear is divided into three main parts – outer ear, middle ear and inner ear.

1. Outer ear:

• It consists of the pinna and the ear canal.
• The pinna collects sound waves from the surroundings and directs them into the ear canal.
• The ear canal carries the sound waves towards the eardrum.

2. Middle ear:

• It begins with the eardrum, a thin, stretched membrane that vibrates when sound waves strike it.
• Behind the eardrum are three small bones called hammer, anvil and stirrup.
• These bones are linked together and act as levers to increase (amplify) the vibrations from the eardrum.
• The last bone passes these vibrations to the inner ear.

3. Inner ear:

• It contains a coiled structure called the cochlea, filled with fluid and sensitive hair cells.
• When vibrations reach the cochlea, they cause movement in the fluid and stimulate the hair cells.
• These hair cells convert the vibrations into electrical signals.
• The signals are carried to the brain by the auditory nerve, and the brain interprets them as sound.

Thus, all three parts of the ear work together to help us hear and understand the sounds around us.

Ans. The process of hearing involves several steps from the source of sound to our brain.

Step 1: Production of sound

• An object or source, such as a bell, guitar or vocal cords, vibrates and produces sound waves in the surrounding medium (usually air).

Step 2: Propagation through air

• These vibrations create compressions and rarefactions in air which travel outward as longitudinal sound waves.
• The sound waves move in all directions from the source.

Step 3: Reaching the outer ear

• When the sound waves reach a person, they are collected by the pinna of the outer ear.
• They then travel through the ear canal and strike the eardrum.

Step 4: Vibrations in the middle ear

• The eardrum starts vibrating with the same frequency as the sound waves.
• These vibrations are passed on to the three small bones in the middle ear (hammer, anvil and stirrup), which amplify the vibrations.
• The last bone transmits the vibrations to the inner ear.

Step 5: Conversion to electrical signals

• In the inner ear, the vibrations reach the fluid-filled cochlea.
• The movement in the fluid bends the tiny hair cells inside the cochlea.
• These hair cells convert the mechanical vibrations into electrical signals.

Step 6: Interpretation by the brain

• The electrical signals travel along the auditory nerve to the brain.
• The brain interprets these signals and we finally experience the sensation of hearing the sound.

Thus, hearing is a complex process involving the ear and the brain working together.

Ans. Our ears are delicate organs that help us hear and maintain balance. If they are damaged, it may lead to temporary or permanent hearing loss. Therefore, it is very important to protect them.

Precautions to protect our ears:

• Avoid very loud sounds: Do not stand near loudspeakers or machines for long periods. Avoid bursting or going very close to loud firecrackers.
• Use earphones carefully: Do not listen to music on earphones or headphones at very high volume. Take breaks if you use them for a long time.
• Do not insert sharp objects: Never insert pins, matchsticks, hair clips or other sharp objects into your ears. They may injure the ear canal or eardrum.
• Keep ears clean and dry: Clean the outer part of the ear gently with a soft cloth. Avoid putting anything deep inside the ear. After a bath, gently dry the ears.
• Avoid self-medication: Do not put ear drops or medicines in your ears without consulting a doctor, especially if there is pain or discharge.
• Consult a doctor in case of problems: If you feel continuous pain, ringing sound, blocked feeling or any discharge from the ear, visit a doctor immediately. Early treatment can prevent serious damage.

By following these precautions, we can keep our ears healthy and protect our hearing ability.

Ans. When Raju hits the drum gently, a soft sound is produced. When he hits it very hard, a loud sound is produced.

Explanation using amplitude and energy:

• When the drum is hit gently, its surface vibrates with a small amplitude. Small amplitude means less energy is given to the vibrating surface, so the sound produced is soft.
• When the drum is hit hard, its surface vibrates with a large amplitude. A larger amplitude means more energy is supplied to the drum surface, and more energy is carried by the sound waves.
• More energy in the sound waves makes the sound louder.

Thus, the loudness of sound increases when the amplitude and the energy of vibrations increase and decreases when they become smaller.

Ans. The child is near a busy road where many vehicles pass, horns are blown and people make noise. This creates noise pollution around his study area.

Reason for lack of concentration:

• Continuous loud and irregular noise from traffic disturbs the child’s mind.
• It becomes difficult for him to read, write and understand lessons clearly.
• Noise makes him feel irritated, tired and unable to focus on studies.

Steps to improve study environment:

• Shift the study table to a quieter room away from the roadside, if possible.
• Keep the windows and doors closed during peak traffic hours to reduce noise entering the room.
• Use thick curtains on windows to absorb some of the sound from outside.
• Plant trees or shrubs outside the house or along the compound wall. Trees act as natural sound barriers.
• Use soft background instrumental music at low volume, if it helps the child concentrate.

By reducing noise levels around the study area, the child can concentrate better and study peacefully.

Ans. The moving train produces loud sounds due to the engine, wheels on the track and movement of air. This sound is irregular and unpleasant, so it can be treated as noise.

Explanation of disturbance:

• The noise from the train is much louder than their voices.
• It mixes with their speech and makes the words unclear.
• They have to speak loudly to be heard, which may tire them and cause throat strain.

How they can communicate better:

• They can sit closer to each other so that they do not have to shout.
• They should speak slowly and clearly, facing each other so that lip movement can also be seen.
• They may choose to talk when the train is moving slowly or when it stops at a station, as noise is less at those times.
• If very important information has to be shared, they can also write it down instead of shouting.

Thus, noise from the moving train acts as a disturbance and makes communication difficult, which is similar to the effect of noise pollution in our surroundings.

Ans. Noise pollution is an important environmental problem today.

Meaning: Noise pollution is the presence of excessive, unwanted or harmful sound in the environment that causes discomfort to humans and other living beings.

Sources:

• Heavy traffic on roads and unnecessary honking.
• Running of machines in factories and construction sites.
• Use of loudspeakers and high-volume music systems.
• Bursting of crackers during festivals and celebrations.
• Noisy household appliances like mixers and vacuum cleaners used carelessly.

Harmful effects:

• Causes headache, stress and mental tiredness.
• Disturbs sleep and leads to lack of proper rest.
• Reduces concentration, especially for students and office workers.
• Long exposure may cause partial or permanent hearing loss.
• May lead to high blood pressure and other health problems.

Control measures:

• Avoid unnecessary use of horns and use only soft horns.
• Use silencers and sound-proofing in industries, machines and vehicles.
• Restrict the use of loudspeakers and follow fixed time limits.
• Plant more trees along roads and around buildings to absorb sound.
• Create silence zones near schools, hospitals and courts.
• Spread awareness among people about harmful effects of noise pollution.

By following these steps, we can reduce noise pollution and make our surroundings healthier and more peaceful.

Ans. People in big cities are often exposed to high levels of noise for long durations. This increases their risk of hearing problems.

Reasons for higher risk:

• Cities have heavy traffic throughout the day, leading to continuous noise from engines and horns.
• There are many factories, workshops and construction sites that use loud machines.
• Frequent use of loudspeakers for social and political events adds to noise levels.
• Some people continuously use earphones at high volume while travelling or working.

Relation with concepts from Chapter 13:

• The chapter explains that loud sounds carry more energy and can damage parts of the ear, especially if a person is exposed to them for a long time.
• Noise pollution causes stress, lack of concentration and may lead to hearing loss if not controlled.
• Delicate structures like the eardrum and hair cells in the inner ear can be permanently damaged by continuous loud noise.

Thus, people living and working in noisy environments in big cities are more likely to develop hearing-related problems if proper precautions are not taken.

Ans.

(a) Production of Sound:

• Sound is a form of energy that produces sensation of hearing.
• It is produced by vibrating objects such as strings, membranes and vocal cords.
• When vibrations stop, sound also stops.

(b) Propagation of Sound:

• Sound travels in the form of longitudinal waves through a material medium like air, water or solids.
• It cannot travel through vacuum.
• Sound travels fastest in solids, slower in liquids and slowest in gases.

(c) Characteristics of Sound:

• Loudness: Depends on amplitude of vibration; greater amplitude means louder sound.
• Pitch: Depends on frequency; higher frequency means higher pitch, lower frequency means lower pitch.
• Quality or timbre: Helps us distinguish sounds from different sources even if they have the same pitch and loudness.
• Human audible range lies roughly between 20 Hz and 20,000 Hz.

(d) Noise Pollution:

• Noises are unwanted, unpleasant and often loud sounds.
• Common sources include traffic, machines, loudspeakers and crackers.
• Noise pollution causes health problems like stress, disturbed sleep and hearing loss.
• It can be controlled by reducing unnecessary noise, using silencers and creating silence zones.

These points cover the main ideas that students should remember from Chapter 13: Sound for their exams.

Ans. Sound is very important in our daily life.

Uses of sound:

• We use sound for communication. We talk and listen to others to share ideas and feelings.
• We enjoy music and songs which help us relax and entertain us.
• Sound of alarms and bells warns us of danger or reminds us of important events like school periods or doorbells.
• Doctors use sound-based instruments, such as stethoscopes, to listen to the heartbeat and breathing of patients.
• Animals also use sound for communication and to warn others of danger.

Problems if hearing is lost:

• It becomes difficult or impossible to communicate through speech, leading to social and emotional problems.
• A person may not hear alarms, horns or warnings and can face dangerous situations on roads or at home.
• Learning in school becomes difficult as the student cannot listen to the teacher properly.
• Hearing loss may cause loneliness and isolation because the person finds it hard to join group activities.

Thus, sound plays a vital role in our life and we must take care to protect our hearing ability.

Ans. Trees act as natural barriers against sound and help in reducing noise pollution.

Justification:

• The leaves, branches and trunks of trees absorb and scatter sound waves coming from noisy roads and machines.
• When sound waves hit a row of trees, some of the sound energy is absorbed by the leaves and branches, and some is reflected back or scattered in different directions.
• This reduces the intensity of sound that reaches houses, schools and other buildings behind the trees.

Examples:

• Planting trees along busy roads and highways reduces traffic noise in nearby residential areas.
• Many schools and hospitals plant trees around their boundary walls to maintain a quieter environment inside.
• Parks with many trees feel much quieter than open areas near roads because trees reduce the noise level.

Therefore, planting more trees is a simple and effective way to help control noise pollution in cities and towns.

Ans. The pitch of a sound depends on its frequency. A higher frequency means a higher pitch and a lower frequency means a lower pitch.

In general:

• Women have shorter and thinner vocal cords compared to men.
• Shorter and thinner vocal cords vibrate more quickly.
• This means that the frequency of vibration of women’s vocal cords is usually higher than that of men.
• Therefore, the sound produced by women has a higher pitch and is perceived as sharper or shriller.

On the other hand, men have longer and thicker vocal cords which vibrate with lower frequency, producing a deeper voice with lower pitch.

Ans. Sound and light are both forms of energy but they have several differences.

Differences:

• Nature of waves:
  • Sound: Sound travels as mechanical waves caused by vibrations of particles.
  • Light: Light travels as electromagnetic waves and does not need particles.
• Need for medium:
  • Sound: Requires a material medium like air, water or solids to travel. It cannot travel through vacuum.
  • Light: Does not require any medium and can travel through vacuum as well as through air, water and glass.
• Speed of travel:
  • Sound: Travels much slower (about 340 m/s in air at room temperature).
  • Light: Travels extremely fast (about 3 × 10⁸ m/s in vacuum).
• Type of waves in common medium:
  • Sound: In air, sound travels as longitudinal waves consisting of compressions and rarefactions.
  • Light: Light waves are transverse waves, where the disturbance is perpendicular to the direction of propagation.

These differences show that although both sound and light provide us information about our surroundings, they behave in very different ways.

Ans. Silence zones are areas where producing loud noise is restricted or banned, especially around hospitals and schools.

Importance around hospitals:

• Patients in hospitals need rest and sleep to recover from illness or after operations.
• Loud noise causes stress, irritation and may increase blood pressure in patients.
• Babies and elderly patients are very sensitive to noise. For their comfort and quick recovery, the environment should be calm and quiet.

Importance around schools:

• Students need peace and concentration while studying in classrooms and libraries.
• Noise from traffic, loudspeakers or construction could disturb classes, making it difficult for students to listen to the teacher.
• Examinations require complete silence so that students can write without distraction.

Therefore, declaring silence zones around hospitals and schools and controlling noise in these areas is essential for the well-being of patients and the learning of students.

Ans. Workers in factories are often surrounded by loud machines and equipment which produce continuous noise.

Effects on workers:

• They may suffer from constant headache, tiredness and stress due to continuous loud noise.
• Noise disturbs their concentration and may lead to mistakes and accidents at work.
• Long-term exposure can damage their ears and lead to partial or permanent hearing loss.
• They may also develop high blood pressure and other stress-related illnesses.

Safety measures:

• Factories should install silencers and use machines that make less noise.
• Workers should be provided with earmuffs or earplugs to protect their ears while working.
• Machines should be maintained regularly so that they run smoothly and make less noise.
• Work shifts should be planned so that no worker is exposed to loud noise for very long hours at a stretch.
• Factory buildings should have sound-proof walls wherever possible.

By taking these measures, the harmful effects of noise on factory workers can be reduced and their health can be protected.

Ans. The human ear is an important sense organ which helps us hear and also maintain balance.

Structure:

• The ear has three main parts – outer ear, middle ear and inner ear.
• The outer ear includes the pinna and ear canal which collect sound.
• The middle ear contains the eardrum and three small bones called hammer, anvil and stirrup.
• The inner ear has the cochlea and the auditory nerve which carry signals to the brain.

Working:

• Sound waves are collected by the pinna and travel through the ear canal to the eardrum.
• The eardrum vibrates and passes the vibrations to the three small bones.
• These bones amplify the vibrations and send them to the cochlea in the inner ear.
• The fluid in the cochlea moves and stimulates hair cells which change vibrations into electrical signals.
• The auditory nerve carries these signals to the brain, where they are interpreted as different sounds.

Care of ears:

• Avoid listening to music at very high volume on earphones or loudspeakers.
• Stay away from very noisy places or use ear protection such as earplugs if you must be there.
• Never insert sharp objects like pins or matchsticks into the ears.
• Keep the outer ear clean and dry using a soft cloth.
• Consult a doctor immediately if there is pain, blockage, discharge or continuous ringing in the ears.

By understanding the structure and working of the ear and by following simple precautions, we can protect our ears and enjoy healthy hearing throughout life.