Chapter 10: Sound

1. How is sound produced?

By vibrating objects.(Kampan karti vastuon dwara).

2. What is vibration?

Rapid to and fro motion of an object.(Vastu ka tezi se aage-peeche hona).

3. Name the sound producing organ in humans.

Larynx or Voice Box.(Larynx ya Swar Yantra).

4. What vibrates in the larynx to produce sound?

Vocal cords.(Vocal cords).

5. Can sound travel through vacuum?

No.(Nahi).

6. Name one medium through which sound can travel.

Air, Water, or Solid (e.g., Steel).(Hawa, Paani, ya Thos).

7. What part of the ear receives sound waves first?

Eardrum (Tympanic membrane).(Kaan ka parda).

8. What determines the loudness of a sound?

Amplitude of vibration.(Kampan ka Aayam).

9. What is the unit of frequency?

Hertz (Hz).

10. What determines the pitch of a sound?

Frequency of vibration.(Kampan ki Aavritti).

11. What is the audible range of frequency for humans?

Approx. 20 Hz to 20,000 Hz.(Lagbhag 20 Hz se 20,000 Hz).

12. Sound with frequency below 20 Hz is called?

Infrasound.

13. Sound with frequency above 20,000 Hz is called?

Ultrasound.

14. What is noise?

Unpleasant sound.(Apriy dhwani).

15. What is the unit of loudness?

Decibel (dB).

16. Give one source of noise pollution.

Loudspeakers, Vehicle horns, Factory machines.(Loudspeaker, Gaadi ke horn, Factory machine).

17. How do trees help reduce noise pollution?

They absorb sound.(Ve aawaz sokhte hain).

1. How is sound produced by musical instruments like sitar and tabla?

• In sitar 🎸 (string instrument), sound is produced by the vibration of the stretched strings when plucked.(Sitar mein, kheenchi hui taaron ke kampan se aawaz aati hai).
• In tabla 🥁 (percussion instrument), sound is produced by the vibration of the stretched membrane (skin) when struck.(Tabla mein, kheenchi hui jhilli (chamdi) ke kampan se aawaz aati hai jab uspe maarte hain).

2. Explain how sound is produced by humans.

• Sound produced by voice box (Larynx).(Aawaz voice box (Larynx) se paida hoti hai).
• Two vocal cords are stretched across larynx with slit between them.(Do vocal cords Larynx mein kheenchi hoti hain).
• When air from lungs is forced through slit, vocal cords vibrate.🗣️🎶(Jab phephdon se hawa slit se nikalti hai, vocal cords vibrate karte hain).
• Vibration produces sound.(Kampan se aawaz paida hoti hai).

3. Explain with an experiment that sound needs a medium to travel.

• Experiment: Electric bell in a glass bell jar connected to vacuum pump.(Prayog: Ek kaanch ke bell jar mein electric bell jo vacuum pump se judi ho).
• Step 1: Ring the bell with air inside jar. We can hear the sound clearly.(Step 1: Jar mein hawa ke saath ghanti bajao. Aawaz saaf sunai degi).
• Step 2: Start removing air using vacuum pump. The sound becomes fainter.(Step 2: Vacuum pump se hawa nikalna shuru karo. Aawaz dheemi ho jayegi).
• Step 3: When most air is removed (vacuum created), the sound becomes extremely feeble or stops, even though bell is still ringing (vibrating).(Step 3: Jab lagbhag saari hawa nikal jaye (vacuum ban jaye), toh aawaz bahut halki ya band ho jayegi, bhale hi ghanti abhi bhi baj rahi ho).
• Conclusion: This shows sound needs a medium (like air) for propagation.🚫🔊🌌 (Nishkarsh: Isse pata chalta hai ki aawaz ko chalne ke liye madhyam chahiye).

4. How do we hear sound through our ears?

• Pinna collects sound waves.
• Waves travel via ear canal to eardrum 🥁.
• Eardrum vibrates.
• Middle ear bones amplify vibrations.
• Inner ear (cochlea) converts vibrations to electrical signals ⚡.
• Auditory nerve sends signals to brain 🧠 for interpretation.

5. Define Amplitude and Frequency of a vibration.

• Amplitude: Max displacement from rest position. Determines Loudness (unit: dB).(Aayam: Rest position se max doori. Loudness (prabalta) batata hai).
• Frequency: Number of oscillations per second. Determines Pitch (shrillness). Unit: Hertz (Hz).(Aavritti: Ek second mein hue dolan. Pitch (taaratva) batata hai. Unit: Hertz).

6. How is loudness related to amplitude? How is pitch related to frequency?

• Loudness & Amplitude: Loudness is directly proportional to the square of the amplitude. Larger amplitude = Louder sound 📢; Smaller amplitude = Softer sound 🤫.(Prabalta amplitude ke square ke anupaatik hai. Zyada amplitude = Zor ki aawaz; Kam amplitude = Dheemi aawaz).
• Pitch & Frequency: Pitch is directly determined by frequency. Higher frequency = Higher pitch (shrill sound, e.g., whistle 🐦); Lower frequency = Lower pitch (deep/grave sound, e.g., drum 🥁).(Taaratva frequency par nirbhar karta hai. Zyada frequency = Ooncha pitch (teekhi aawaz); Kam frequency = Neecha pitch (gehri aawaz)).

7. Differentiate between audible and inaudible sounds.

• Audible Sound: Sound humans can hear. Frequency range: ~20 Hz to 20,000 Hz.👂✅ (Manushya dwara suni ja sakne wali aawaz. Frequency: ~20 Hz se 20,000 Hz).
• Inaudible Sound: Sound humans cannot hear.
  • *Infrasound:* Frequency < 20 Hz.
  • *Ultrasound:* Frequency > 20,000 Hz.
  👂❌ (Manushya dwara na suni ja sakne wali aawaz. Frequency 20 Hz se kam ya 20,000 Hz se zyada).

8. Differentiate between Noise and Music.

• Noise 😠: Unpleasant sound, usually from irregular vibrations. Ex: Construction noise, traffic horns.(Apriy dhwani, aniyamit kampan se. Udaharan: Construction ka shor, gaadi ke horn).
• Music 🎶: Sound pleasant to hear, usually from regular, periodic vibrations. Ex: Sound from musical instruments.(Priy dhwani, niyamit kampan se. Udaharan: Sangeet vadyayantra ki aawaz).
• Note: Sometimes even music becomes noise if played too loud.(Dhyan dein: Kabhi kabhi music bhi shor ban jaata hai agar bahut tez bajaya jaye).

9. List four sources of noise pollution in your surroundings.

• Sounds of vehicles (horns 📢, engines 🚗).
• Loudspeakers 📣 at functions or religious places.
• Machines operating in nearby factories 🏭 or construction sites 🚧.
• Home appliances like mixer grinder, vacuum cleaner, desert cooler 🌬️.
• Bursting of firecrackers 🎆.

10. What are the harms of noise pollution?

• Causes health problems like lack of sleep (insomnia), hypertension (high BP 💓⬆️), anxiety 😥.
• Can lead to temporary or permanent hearing impairment (bahrapan 👂❌).
• Reduces concentration and work efficiency.
• Causes stress and irritation.

11. Suggest measures to limit noise pollution.

• Use silencers in vehicles and machines.
• Reduce honking 📢🚫.
• Play music/TV at low volumes 🎶⬇️.
• Plant trees 🌳 (absorb sound).
• Locate noisy industries away from homes.
• Restrict use of loudspeakers.

1. Explain how sound is produced and propagates through a medium like air.

Production: Sound is produced by **vibrating** objects. A vibration is a rapid back-and-forth motion.

Propagation Through Air (Hawa Mein Sancharan):

• When an object (e.g., a drum membrane 🥁) vibrates, it pushes the air particles immediately next to it forward, creating a region of **high pressure (compression)**. (Jab vastu vibrate karti hai, woh apne paas ki hawa ke kanon ko aage dhakelti hai, jisse high pressure (compression) ka kshetra banta hai).
• When the vibrating object moves backward, it creates a region of **low pressure (rarefaction)**. (Jab vastu peeche jaati hai, toh low pressure (rarefaction) ka kshetra banta hai).
• The vibrating air particles pass on their vibration to the next layer of particles. (Kampan karte hawa ke kan apna kampan agle kanon tak pahunchate hain).
• This creates a series of compressions and rarefactions that travel outwards from the source.
• This travelling disturbance, carrying energy through the vibration of medium particles, is a **sound wave** 〰️.
• The particles themselves don’t travel far, they just vibrate back and forth about their mean position, transferring the energy. (Kan khud door nahi jaate, bas apni jagah par aage-peeche vibrate karte hain, urja transfer karte hain).
• This wave reaches our ear, causing the eardrum to vibrate, allowing us to hear.

2. Describe the structure and working of the human ear.

The human ear helps us hear sound and is divided into three parts:

1. Outer Ear:

• Pinna: The visible outer part. Collects sound waves from surroundings and funnels them into the ear canal.(Bahari dikhne wala hissa. Aawaz ki tarangon ko ikattha karke ear canal mein bhejta hai).
• Ear Canal (Auditory Canal): A tube that leads inwards.

2. Middle Ear:

• Eardrum (Tympanic Membrane) 🥁: A thin, stretched membrane at the end of the ear canal. Vibrates when sound waves strike it.(Ear canal ke ant mein patli jhilli. Aawaz takrane par vibrate karti hai).
• Ear Ossicles (Tiny Bones): Three small bones – Hammer (Malleus), Anvil (Incus), Stirrup (Stapes). They amplify (increase) the vibrations received from the eardrum.(Teen chhoti haddiyan – Hammer, Anvil, Stirrup. Eardrum se mili vibrations ko badhati hain).

3. Inner Ear:

• Cochlea 🐌: A coiled, fluid-filled structure resembling a snail shell. It contains nerve cells sensitive to vibrations.(Ghonge jaisi sanrachna jismein drav bhara hota hai. Ismein vibration ke prati sensitive nerve cells hote hain).
• Conversion to Signals: The amplified vibrations from middle ear travel through the cochlear fluid and stimulate the nerve cells. These cells convert the vibrations into electrical signals ⚡.
• Auditory Nerve: Transmits these electrical signals to the brain 🧠.
• Brain: Interprets the signals as the sound we perceive.

3. Define Amplitude, Time Period, and Frequency. Explain how they relate to sound characteristics (Loudness and Pitch).

These describe vibrations/oscillations:

• Amplitude: Maximum displacement from the rest position during vibration. (Kampan ke dauran rest position se adhiktam doori).
  • Relation to Sound: Determines **Loudness**. Larger Amplitude = Louder Sound 📢. Measured in decibels (dB).
• Time Period (T): Time taken for one complete oscillation/vibration. (Ek poora dolan/kampan karne mein laga samay). Unit: second (s).
• Frequency (f): Number of oscillations/vibrations per second. (Ek second mein hue dolano/kampano ki sankhya). Unit: Hertz (Hz). (Frequency = 1 / Time Period).
  • Relation to Sound: Determines **Pitch** (shrillness). Higher Frequency = Higher Pitch (shriller sound 🐦). Lower Frequency = Lower Pitch (deeper sound 🥁).

Example: If a pendulum completes 10 oscillations in 20 seconds, its Time Period is 20s/10 = 2s, and its Frequency is 10 oscillations / 20s = 0.5 Hz.

4. Differentiate between Music and Noise. Can music become noise sometimes?

Both are sounds, but differ in their effect on our ears:

Music 🎶:

• Sound that is pleasant and soothing to the ear. (Sunne mein achhi aur shant karne wali aawaz).
• Produced by regular, periodic vibrations. (Niyamit, आवर्ती kampanon se paida hoti hai).
• Examples: Sounds from well-played musical instruments (guitar 🎸, flute 🎵, violin).

Noise 😠📢:

• Sound that is unpleasant, jarring, or unwanted. (Na-pasand, Karkash, ya anchaahi aawaz).
• Produced by irregular, non-periodic vibrations. (Aniyamit, अनावर्ती kampanon se paida hoti hai).
• Examples: Honking cars, construction sounds 🚧, loud arguments.

Can Music Become Noise? Yes! ✅

• Even sounds considered musical can become noise if they are too loud 🔊⬆️ or if they are disturbing to someone. (Ha! Agar sangeet bhi bahut tez ho ya kisi ko pareshan kare, toh woh shor ban sakta hai).
• Example: Listening to music at a very high volume through headphones can be harmful noise for your ears and disturbing noise for others.

5. What is Noise Pollution? Explain its main sources and harmful effects.

Noise Pollution: Presence of excessive or undesirable sound levels in the environment that cause discomfort or health issues.

Sources (Strot):

• Transportation: Vehicle horns 📢, engines (trucks, buses 🚌, planes ✈️).
• Industrial: Machines in factories 🏭, construction sites 🚧.
• Household: Loud TV/Music 🎶⬆️, Mixer grinders, Coolers.
• Social Events: Loudspeakers 📣, Firecrackers 🎆.

Harmful Effects (Haanikarak Prabhav):

• Health Issues: Lack of sleep (Insomnia 😴❌), Hypertension (High BP 💓⬆️), Anxiety 😥, Stress.
• Hearing Impairment 👂❌: Exposure to loud noise continuously can cause temporary or permanent deafness.
• Reduced Concentration: Affects work and study performance.

6. Describe measures to limit noise pollution.

We can reduce noise pollution by:

• Controlling Source Noise:
  • Installing Silencers in vehicles, aircraft engines, industrial machines, and home appliances.
  • Designing machines to run quieter.
  (Source par hi shor kam karna: Silencer lagana, machine design sudharna).
• Controlling Transmission Path:
  • Planting trees 🌳 along roads/buildings – they absorb sound effectively.
  • Using sound-absorbing materials in buildings (like carpets, curtains, false ceilings).
  (Shor ke raaste ko rokna: Ped lagana, sound-absorbing material istemal karna).
• Reducing Exposure:
  • Locating noisy industries/airports away from residential areas 🏠🚫🏭.
  • Restricting use of loudspeakers and vehicle horns 📢🚫 in sensitive zones (hospitals, schools) and during certain hours.
  • Using ear protection (earplugs/earmuffs) in noisy environments.
  (Shor ke exposure ko kam karna: Noisy industries door banana, loudspeaker/horn kam istemal karna, ear protection use karna).
• Personal Habits:
  • Running TV/music systems at low volumes 🎶⬇️.
  • Avoiding unnecessary honking.
  (Apni Aadatein sudharna: TV/Music dheere chalana, bewajah horn na bajana).

7. Explain the difference between Pitch and Loudness of sound.

Pitch and Loudness are two main characteristics of sound:

Pitch (Taaratva):

• How high or low (shrill or grave) a sound appears to be. (Aawaz kitni patli/teekhi ya moti/gehri hai).
• Determined primarily by the **Frequency** of vibration. 🎶➡️Hz
• High Frequency = High Pitch (e.g., a whistle, a woman’s voice usually). 🐦
• Low Frequency = Low Pitch (e.g., a drum, a man’s voice usually). 🥁
• Example: A bird’s chirp has high pitch, a lion’s roar 🦁 has low pitch.

Loudness (Prabalta):

• The intensity or energy of the sound as perceived by the ear. (Kaan dwara mehsoos ki jaane wali aawaz ki teevrata ya urja).
• Determined primarily by the **Amplitude** of vibration.
• Large Amplitude = Loud Sound 📢.
• Small Amplitude = Soft/Feeble Sound 🤫.
• Measured in **decibels (dB)**.
• Example: A whisper is soft (low amplitude), a shout is loud (high amplitude).

These two are independent characteristics. A sound can be high pitch & loud, high pitch & soft, low pitch & loud, or low pitch & soft.

8. Sound cannot travel in vacuum. How can you demonstrate this?

This can be demonstrated using the Bell Jar Experiment:

1. Setup: Place an electric bell inside an airtight glass bell jar. Connect the bell to a power supply outside the jar. Connect the bell jar to a vacuum pump which can remove air from inside.
(Ek hawa-band kaanch ke bell jar ke andar ek electric bell rakhein. Bell ko bahar power supply se jodein. Bell jar ko ek vacuum pump se jodein jo andar se hawa nikaal sake).
2. Observation 1 (With Air): Switch on the electric bell. You will be able to clearly hear the ringing sound through the glass jar because air is present inside as a medium.
(Electric bell on karein. Aapko jar ke andar se ghanti ki aawaz saaf sunai degi kyunki andar hawa madhyam ke roop mein maujood hai).
3. Observation 2 (Removing Air): Start the vacuum pump to gradually remove the air from the bell jar. As the air is pumped out, the sound of the ringing bell becomes fainter and fainter.
(Vacuum pump shuru karke dheere-dheere jar se hawa nikalna shuru karein. Jaise jaise hawa nikalti jayegi, ghanti ki aawaz dheemi hoti jayegi).
4. Observation 3 (Vacuum): When most of the air has been removed (a near vacuum is created), the sound becomes extremely feeble or cannot be heard at all, even though you can still see the hammer striking the gong (meaning the bell is vibrating).
(Jab lagbhag saari hawa nikal jaye (vacuum ban jaye), toh aawaz bahut hi halki ho jaati hai ya bilkul sunai nahi deti, bhale hi aap hammer ko gong par lagte hue dekh sakte hain (matlab bell vibrate kar rahi hai)).
5. Conclusion: This experiment demonstrates that sound requires a material medium (like air) for its propagation and cannot travel through a vacuum. 🚫🔊🌌

9. What is the audible range for humans? Can animals hear sounds that we cannot?

Audible Range for Humans 👂✅:

• The human ear is sensitive to sound waves only within a specific range of frequencies.
• This range is approximately **20 Hertz (Hz) to 20,000 Hertz (20 kHz)**.
• We cannot hear sounds with frequencies below 20 Hz (Infrasound) or above 20,000 Hz (Ultrasound).

Animal Hearing Ranges:

• Yes, many animals can hear sounds outside the human audible range 👂❌ (for us).
• Ultrasound (>20 kHz): Dogs 🐕 can hear sounds up to about 45 kHz. Bats 🦇 produce and hear very high frequency ultrasound (up to 100 kHz or more) for echolocation (finding prey/obstacles). Dolphins 🐬 also use ultrasound.
(Haan, kai janwar manushya ki shravya range ke bahar ki aawazein sun sakte hain. Kutte, chamgadad, dolphin ultrasound sun sakte hain).
• Infrasound (<20 Hz): Elephants 🐘, rhinoceroses, whales can communicate using low-frequency infrasound over long distances.
(Haathi, gainde, whale lambi doori par baat karne ke liye kam frequency wale infrasound ka istemal kar sakte hain).

10. List the sources of noise pollution and suggest some preventive measures.

Noise pollution is caused by excessive unwanted sound.

Sources (Strot):

• Traffic Noise (vehicles 🚗🚚, horns 📢)
• Industrial Noise (factory machines 🏭)
• Construction Noise 🚧
• Loudspeakers 📣 & Music Systems 🎶⬆️
• Home Appliances (mixer, cooler)
• Airports (aircraft noise ✈️)
• Firecrackers 🎆

Preventive Measures (Roktham Ke Upay):

• Installing Silencers in engines/machines.
• Reducing use of Horns.
• Playing music/TV at low volume.
• Planting Trees 🌳 (sound absorption).
• Setting up industries away from homes.
• Enforcing rules on loudspeaker usage.
• Using soundproofing materials.
• Wearing ear protection in noisy jobs.