Sound and Its Properties
Guide for Reading
What is Sound?
- Sound waves begin with a vibration.
- Sound waves carry energy through a medium without the particles of the medium traveling along.
- A common medium for sound is air.
- Sound is defined as a disturbance that travels through a medium as a longitudinal wave.
Production of Sound Waves
- A vibrating object creates compressions and rarefactions that travel through the air as longitudinal waves.
- Mechanism of Sound Production:
- When a person speaks or sings, they force air from their lungs up through their voice box, also known as the larynx.
- The larynx consists of two folds of tissue called vocal cords.
- The forced air rushes by the vocal cords, making them vibrate.
- These vibrations produce compressions and rarefactions in the air.
- The air carries these longitudinal waves to other people's ears and the speaker's own ears.
Properties of Sound Waves
- Diffraction of Sound Waves:
- Sound waves can diffract as they pass through small spaces, similar to how water waves behave.
- Due to diffraction, one can hear sounds from around corners.
Factors Affecting the Speed of Sound
- The speed of sound is influenced by several factors:
- Elasticity:
- Defined as the ability of a material to bounce back after being disturbed.
- Example: A rubber band is an elastic substance.
- Sound travels more quickly in mediums with a high degree of elasticity, because the particles return to their original positions rapidly after being compressed.
- Density:
- Defined as the amount of matter (mass) in a given volume of space.
- Sound travels more slowly in denser materials, such as metals.
- Temperature:
- The temperature of the medium affects the speed of sound significantly.
- At 20°C (room temperature), sound travels at approximately 340 m/s.
- Sound travels more slowly at lower temperatures and faster at higher temperatures.
REVISE AND REINFORCE
Factors Affecting the Speed of Sound
| Factor | Change in Factor | Effect on Speed of Sound |
|---|---|---|
| Elasticity | Increase in elasticity | Sound travels faster |
| Density | Increase in density | Sound travels slower |
| Temperature | Decrease in temperature | Sound travels slower |
Explanation of Sound Travel
- Sound travels as compressions and rarefactions in a medium (e.g., air) due to the vibrations of an object, which causes surrounding particles to move and transmit the sound energy without actually moving the particles along the way.