Sound ശബ്ദം
The chapter opens in a school laboratory. A teacher presses the switch of an electric bell that sits inside a glass bell jar (ബെൽജാർ) connected to a vacuum pump (വാക്വം പമ്പ്). The hammer is striking the gong – yet she says, “The bell is working, but I can't hear any sound!” Why? By the end of this chapter you will know. You will find out how sound is produced by vibrating objects – from a tuning fork to a chenda, a veena and your own voice box. You will see how it travels through air, water and solids but not through a vacuum, and why you see the lightning before you hear the thunder. You will learn how the ear hears, how to protect it, the difference between music and noise, and what we can do about noise pollution. This animated self-study guide starts from the basics – vibrations, particles, waves and speed – explains every idea with Kerala examples, answers every textbook question, and ends with a revision sheet and a model test.
The chapter in one picture
Left: the prongs of a tuning fork (ട്യൂണിങ് ഫോർക്ക്) vibrate (കമ്പനം). Each time a prong moves out, it squeezes the air particles next to it into a crowded band – a compression, C (മർദം കൂടിയ മേഖല). Each time it moves back, it leaves a thinned-out band – a rarefaction, R (മർദം കുറഞ്ഞ മേഖല). The bands travel to the ear and make the eardrum (കർണ്ണപുടം) vibrate. Watch the red particle: it only moves to and fro about its own place; the air does not flow from the fork to the ear – only the disturbance travels. (Slow motion: a real fork vibrates hundreds of times a second.) Right: as the vacuum pump removes the air from the bell jar, the sound meter outside falls almost to zero – yet the hammer keeps striking. Sound needs a medium (മാധ്യമം); it cannot travel through a vacuum (ശൂന്യത). Let the air back in and the sound returns. (The meter is a simple model, not real measurements.)
How to use this guide
🎬 Watch the animations
Prongs vibrate, air particles crowd together and spread apart, eardrums shake and bells fall silent – one step at a time. Press Next ▶ or ▶▶ Auto play. Animations pause by themselves when you scroll away; click a lab to restart its clock.
🧪 Do the virtual experiments
Pluck rubber bands, pump air out of a jar, race sound through steel, water and air, and time the thunder after a lightning flash. The textbook activities have no fixed readings, so the numbers in the labs are sample values worked out with real physics.
🔇 Silent by default
The pages make no sound on their own. Only two labs (pitch and loudness on page 3, music and noise on page 9) have a clearly marked “▶ Play tone” button. It plays a short, soft tone only when you click it. Keep the volume low.
✍️ Try before you see
Every numerical is laid out the exam way: Given → Formula → Substitution → Answer. Use 💡 Show a hint first and work in your notebook. Then open ✅ Show final answer.
📖 Textbook words
Purple മലയാളം words are the exact terms used in your textbook (pages 157–170), so you can match this guide with your book and write answers in either language.
Learning path
Follow the pages in order. If you are already confident with vibrations, particles of matter, waves and speed = distance ÷ time, you can skim pages 1–4. Still try their quizzes, because the chapter uses these ideas on every page.
Quick glossary (Malayalam ↔ English)
| Textbook term | English | Meaning |
|---|---|---|
| ശബ്ദം | Sound | The chapter title: a form of energy that produces the sensation of hearing |
| ശ്രവണബോധം | Sensation of hearing | What we feel when sound reaches the brain through the ear |
| ഊർജരൂപം | Form of energy | Sound, light, heat and electricity are all forms of energy |
| കമ്പനം | Vibration | Rapid to-and-fro motion about a middle position; every sound starts with one |
| നേർരേഖാചലനം | Straight-line (linear) motion | Motion along a straight line, such as a coconut falling – not to and fro |
| ശബ്ദസ്രോതസ്സ് / ശബ്ദസ്രോതസ്സുകൾ | Source(s) of sound | Objects that produce sound by vibrating |
| ട്യൂണിങ് ഫോർക്ക് | Tuning fork | A two-pronged steel fork that vibrates and gives a steady note when struck on a rubber pad |
| സംഗീതോപകരണങ്ങൾ | Musical instruments | Veena, violin, chenda, tabla, mridangam, harmonium, odakkuzhal (flute)… |
| പ്രധാന ഭാഗം / അനുബന്ധ ഭാഗങ്ങൾ | Main (vibrating) part / associated parts | The part that starts the vibration (string, skin, reed, air column) / the body and air that vibrate along with it |
| സ്വനപേടകം | Larynx (voice box) | The organ at the top of the windpipe where our voice is produced |
| സ്വനതന്തുക്കൾ | Vocal cords | Two folds in the larynx that vibrate when we speak or sing |
| ശബ്ദപ്രേഷണം | Propagation of sound | The travelling of sound from the source through a medium |
| മാധ്യമം | Medium | The substance – solid, liquid or gas – through which sound travels |
| ശൂന്യത | Vacuum | A space with no particles of matter (no air); sound cannot travel through it |
| ഖരം / ദ്രാവകം / വാതകം | Solid / liquid / gas | The three states of matter; sound is fastest in solids and slowest in gases |
| ശബ്ദവേഗം | Speed of sound | Distance travelled by sound in one second: about 350 m/s in air, 1500 m/s in water, 6000 m/s in steel |
| താപനില | Temperature | How hot or cold a medium is; sound travels faster when it is warmer |
| ചെവിയും ശ്രവണവും | Ear and hearing | The textbook section on how we hear (pages 165–167) |
| ചെവിക്കുട | Outer ear (pinna) | The visible part of the ear that collects sound |
| കർണ്ണനാളം | Ear canal | The tube that carries sound from the outer ear to the eardrum |
| കർണ്ണപുടം | Eardrum (tympanum) | A thin membrane that vibrates when sound reaches it |
| ആന്തരകർണ്ണം | Inner ear | The part that receives the vibrations and sends signals to the brain |
| ഡയഫ്രം | Diaphragm | A thin stretched sheet (like the balloon in the mustard-seed activity) that vibrates |
| മർദവ്യതിയാനങ്ങൾ | Pressure variations | The rise and fall of air pressure that a vibrating object creates |
| മർദം കൂടിയ മേഖല (C) | Compression | A region where the particles are crowded together – higher pressure |
| മർദം കുറഞ്ഞ മേഖല (R) | Rarefaction | A region where the particles are spread apart – lower pressure |
| ശ്രവണേന്ദ്രിയം | Organ of hearing | The ear – one of the three things needed to hear (source, medium, organ of hearing) |
| ലോക ശ്രവണദിനം | World Hearing Day | 3 March, a day to spread awareness about hearing care |
| ഓഡിയോമീറ്റർ / ഓഡിയോളജിസ്റ്റ് | Audiometer / audiologist | A machine that tests hearing / a specialist who tests and treats hearing problems |
| ശ്രവണ സഹായി | Hearing aid | An electronic device that helps a person with hearing loss to hear |
| ചെവിയുടെ സംരക്ഷണം | Protection of the ear | Ear care: nothing inside the ear, no very loud sounds, see a doctor for pain |
| സംഗീതം / ഒച്ച | Music / noise | Pleasant sound from regular vibrations / unpleasant sound from irregular vibrations |
| ശബ്ദമലിനീകരണം | Noise pollution | Unnecessary, unbearable sound that harms people and other living things |
| ഇയർ മഫ് / ഇയർ പ്ലഗ് | Ear muff / ear plug | Protectors worn over / inside the ears near loud machines |
| ബെൽജാർ · വാക്വം പമ്പ് | Bell jar · vacuum pump | A glass dome on a plate · a pump that removes air from it |
| ശബ്ദമിശ്രണം | Sound mixing | Combining recorded sounds for a film – Resul Pookutty won an Oscar for it |
| പ്രവർത്തനം · സയൻസ് ഡയറി | Activity · science diary | Things to do, and the notebook where you write what you observed |
| വിലയിരുത്താം · തുടർപ്രവർത്തനങ്ങൾ | Let us assess · extended activities | The end-of-chapter questions and projects (solved on page 11) |
🌐 Explore online (optional)
Everything in this guide works offline: each page is a single file with no internet needed. Some pages also have blue “🌐 Explore online” boxes. They link to free websites and interactive simulations, including the PhET “Sound Waves” simulation that your textbook mentions on page 163. Those links need internet and open in a new tab. All of them are collected in the resources hub on page 12.
- 📄 Physics Tutorial: Sound Waves The Physics Classroom
The full set of sound lessons: nature of sound, its properties, resonance and musical instruments. - 📄 Sound (topic page) Science Learning Hub (NZ)
A collection of short articles and activities on sound, hearing and music. - 📄 Sound: the science of waves Explain that Stuff
A friendly introduction to what sound is, how it travels and how we use it.
Made for self-learning. Works offline – every page is a single file. Study material prepared by Claude for Madhu's family study folder, October 2026.