SPI Physics · Sound
Hearing, Speech and Uses of Sound
We speak when our vocal cords vibrate and hear when the ear passes vibrations from the eardrum through three tiny bones to the inner ear; reflected sound and ultrasound are put to work in halls, hospitals and ships.
Why this matters
Four questions in the bank, all EASY: what vibrates in the voice box, what the three bones of the middle ear do, why a curved soundboard stands behind a stage, and which waves echocardiography uses. Each is a single fact, and the two tables below hold all of them.
Concept 1 of 2: How we speak and how we hear
Speaking and hearing are both about vibrations. In the throat, stretched cords vibrate to make sound; in the ear, a thin skin vibrates when sound arrives, and a chain of tiny bones passes those vibrations inwards, making them stronger on the way.
Definition
- Our voice comes from the vocal cords, two stretched folds in the voice box (larynx), which vibrate as air from the lungs passes.
- In the ear, the eardrum vibrates first. The three bones of the middle ear (hammer, anvil, stirrup) amplify the vibrations; they do not change the pitch or frequency.
- The cochlea in the inner ear turns vibrations into electrical signals, which the auditory nerve carries to the brain.
| Part | Its job |
|---|---|
| Vocal cords (in the larynx) | Vibrate to make the voice |
| Pinna (outer ear) | Collects sound and sends it down the ear canal |
| Eardrum | A thin membrane that vibrates when sound reaches it |
| Hammer, anvil and stirrup (middle ear) | Amplify the vibrations and pass them to the inner ear The stirrup is the smallest bone in the body. |
| Cochlea (inner ear) | Turns vibrations into electrical signals |
| Auditory nerve | Carries the signals to the brain |
Outer ear collects, middle ear amplifies, inner ear converts.
Practice this conceptself-check · 4 quick reps
The same idea in a practice question:
Practice questionEasy
Example 1 · Sound · Hearing, Speech and Uses of Sound
The function of three bones present in the middle of ear is to
The middle ear bones raise the pitch
The three bones only make the vibrations stronger. The frequency, and so the pitch, stays the same.
The eardrum makes the voice
The eardrum vibrates when we HEAR. When we speak, it is the vocal cords in the larynx that vibrate.
Concept 2 of 2: Uses of reflected sound and ultrasound
Sound bounces off hard surfaces just as light does off a mirror, so curved boards and ceilings can steer it round a hall. Ultrasound, too high for us to hear, bounces back from things we cannot see, so its echoes can draw a picture of a heart or the sea bed.
Definition
- A curved soundboard stands behind the stage with the speaker near its focus. It reflects the sound so it spreads evenly across the hall.
- An echo is a reflected sound heard separately. The ear keeps a sound for about 0.1 s, so in air the wall must be at least about 17 m away.
- Ultrasound (above 20 kHz) gives images and measures distances from its echoes.
| Use | How sound is used |
|---|---|
| Curved soundboard, curved ceiling | Reflect sound evenly to every part of a hall |
| Megaphone, horn | Reflections send the sound forward in one direction |
| Stethoscope | The heartbeat's sound is reflected along the tube to the ear |
| Echocardiography | Ultrasound echoes give an image of the heart Ultrasound, not X-rays. |
| Ultrasonography | Ultrasound images of organs and of a baby in the womb |
| SONAR | Ultrasound echoes find the depth of the sea and locate submarines |
| Bats | Find their way and their prey by ultrasound echoes |
Reflected sound is used in halls; ultrasound echoes are used in hospitals and at sea.
Practice this conceptself-check · 4 quick reps
The same idea in a practice question:
Practice questionEasy
Example 2 · Sound · Hearing, Speech and Uses of Sound
Curved soundboard may be placed behind the stage because:
A soundboard absorbs sound
A soundboard reflects sound, and its curve spreads it across the whole width of the hall, not to one spot.
Heart scans use X-rays
Echocardiography uses ultrasound echoes. Infrasound cannot form an image, and no X-rays are used.
Expecting an echo from a near wall
A wall closer than about 17 m sends the sound back within 0.1 s, so it merges with the original sound and no separate echo is heard.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
How we speak and how we hear6 rows
| Part | Its job |
|---|---|
| Vocal cords (in the larynx) | Vibrate to make the voice |
| Pinna (outer ear) | Collects sound and sends it down the ear canal |
| Eardrum | A thin membrane that vibrates when sound reaches it |
| Hammer, anvil and stirrup (middle ear) | Amplify the vibrations and pass them to the inner ear The stirrup is the smallest bone in the body. |
| Cochlea (inner ear) | Turns vibrations into electrical signals |
| Auditory nerve | Carries the signals to the brain |
Outer ear collects, middle ear amplifies, inner ear converts.
Uses of reflected sound and ultrasound7 rows
| Use | How sound is used |
|---|---|
| Curved soundboard, curved ceiling | Reflect sound evenly to every part of a hall |
| Megaphone, horn | Reflections send the sound forward in one direction |
| Stethoscope | The heartbeat's sound is reflected along the tube to the ear |
| Echocardiography | Ultrasound echoes give an image of the heart Ultrasound, not X-rays. |
| Ultrasonography | Ultrasound images of organs and of a baby in the womb |
| SONAR | Ultrasound echoes find the depth of the sea and locate submarines |
| Bats | Find their way and their prey by ultrasound echoes |
Reflected sound is used in halls; ultrasound echoes are used in hospitals and at sea.
Watch out for (5)
- The middle ear bones raise the pitch→ How we speak and how we hear
- The eardrum makes the voice→ How we speak and how we hear
- A soundboard absorbs sound→ Uses of reflected sound and ultrasound
- Heart scans use X-rays→ Uses of reflected sound and ultrasound
- Expecting an echo from a near wall→ Uses of reflected sound and ultrasound
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