Physics Ch. 2

What is ultrasound?

Sound with a frequency above the human hearing range.

What is sound?

A mechanical, longitudinal wave that carries energy through a medium.

What type of wave is sound?

A mechanical, longitudinal wave.

Why can't sound travel through a vacuum?

Sound needs a medium with particles to transfer its energy.

What do sound waves carry?

Energy.

What are the two parts of a sound wave?

Compressions and rarefactions.

What is a compression?

A region where particles are close together with increased pressure and density.

What is a rarefaction?

A region where particles are spread apart with decreased pressure and density.

How does sound travel through a medium?

Particles vibrate and transfer energy from one particle to the next.

How does sound travel?

In a straight line.

What are acoustic variables?

Pressure, density, and distance.

What is pressure?

The concentration of force in a specific area.

What are acoustic parameters?

Measurements that describe the characteristics of a sound wave.

What are the seven acoustic parameters?

Period, frequency, wavelength, speed, amplitude, power, and intensity.

What is the difference between acoustic variables and acoustic parameters?

Variables identify a sound wave, while parameters describe the wave's characteristics.

What is a transverse wave?

A wave in which particles move perpendicular to the direction the wave travels.

What is a longitudinal wave?

A wave in which particles move parallel to the direction the wave travels.

Is sound transverse or longitudinal?

Longitudinal.

What does "in phase" mean?

Two waves have corresponding parts occurring at the same time and location.

What does "out of phase" mean?

Two waves have corresponding parts occurring at different times or locations.

What is interference?

When two or more waves overlap and combine.

What is constructive interference?

When waves combine to produce a wave with greater amplitude.

What is destructive interference?

When waves combine to produce a wave with lesser amplitude.

What happens when two in-phase waves interfere?

Their amplitudes add together, producing constructive interference.

What happens when two out-of-phase waves interfere?

Their amplitudes partially or completely cancel, producing destructive interference.

Can waves of different frequencies interfere?

Yes. They can produce both constructive and destructive interference.

What does PDD stand for?

Pressure, Density, and Distance.

If force and area both increase by the same amount, what happens to pressure?

Pressure remains unchanged.

What three things are needed for sound to travel?

A source of vibration, a medium, and energy.

Why is sound called a mechanical wave?

Because it requires matter, or a medium, to travel.