4.1 Sound

The medium through which a sound wave passes can be a solid, a liquid, or a gas. Properties of a wave might change when it moves from one medium to another. What happens to the speed of a sound wave when the medium changes from a gas to a solid?

• It speeds up.
• It slows down.
• It remains the same.
• It speeds up and then slows down.

When sound waves move through a medium, in what direction do the particles in the medium move?

• The particles always move side to side.
• The particles always move up and down.
• The particles always move in the same direction as the wave.
• The particles always move perpendicular to the direction of the wave.

What role does the inner ear play in hearing sounds?

• It blocks out unwanted sounds.
• It converts vibrations into electrical signals.
• It helps determine if a sound is in front of or behind you.
• It reflects high and low frequencies back and their source.

What property of a wave changes to create the Doppler effect?

• its speed
• its medium
• its amplitude
• its frequency

A large explosion can damage a person's hearing. What causes this damage?

• Heat from the explosion burns the eardrum.
• Transverse waves from the explosion cause vibrations that damage the ear.
• The explosion triggers smaller explosions inside the ear.
• Compression waves from the explosion cause vibrations that damage the ear.

The diagram shows a sound wave moving through air. What property of the wave would change if the distance between points N and M was longer?

• The pitch would decrease.
• The loudness would decrease.
• The amplitude would increase.
• The frequency would increase.

Which statement best describes how humans hear sound?

• Sound waves enter the ear canal and increase in amplitude, which causes you to hear the sound.
• Sound waves cause parts of the ear to vibrate until the waves are converted to electrical signals, which are sent to the brain.
• Sound waves travel into people ears, then the eardrum sends the sound waves to the brain.
• Sound waves become sounds when they strike the eardrum inside the ear.

Josh observed a bolt of lightning during a thunderstorm. It took more than 15 sounds for Josh to hear the sound of thunder. Why did Josh see the lighting strike before he heard the thunder?

• Thunder always takes 15 seconds to travel through the air after lighting strikes.
• Light waves from the lightning and sound waves from the thunder moved through different media.
• Light waves are electromagnetic waves that travel much faster than mechanical waves, such as the sound waves he heard as thunder.
• The conditions in the air at the time allowed light waves to move faster than the sound waves he heard as thunder.

A few boys are sledding on snow in their favorite park. They notice that it is harder to hear someone shouting from the top of the hill to the bottom than it is in the summertime. What factor is most likely affecting the sound of their shouting?

• altitude
• temperature
• frequency
• pressure

What happens to the frequency of a sound wave as it moves from a liquid to a gas medium?

• The frequency fluctuates.

• The frequency remains the same.

• The frequency decreases.

• The frequency increases.