# Physics Ch 26

## 20 terms

### Pitch

description of our subjective impression about the frequency of sound
the property of sound that varies directly with variation in the frequency of vibration

### Sound intensity

Amount of energy that a sound wave brings to a unit area every second.
objective - measured by instruments

### Resonance

when there is a force to pull it back to its starting position and enough energy to keep it vibrating

### Shock wave

The cone-shaped disturbance created by an object moving at supersonic speed through a fluid.

### Infrasonic

sound waves with frequencies below 20 hertz

### Loudness

physiological sensation sensed in the brain - more mental

### Beats

when two tones of slightly different frequency are sounded together - it is that fluctuation in the loudness of the combined soudns

### Bow wave

The V-shaped wave produced by an object moving on a liquid surface faster than the wave speed.

### Destructive interference

the interference that occurs when two waves combine to make a wave with a smaller amplitude

### Ultrasonic

sound waves with frequencies above 20,000 hertz

### Decibel

unit of intensity for sound

### Supersonic

faster than the speed of sound

### Natural frequency

A frequency at which an elastic object naturally tends to vibrate, so that minimum energy is required to produce a forced vibration or continue vibration at that frequency.

### Compression

the part of a longitudinal wave where the particles of the medium are close together

### Oscilloscope

an instrument that can be used to record voice vibrations and show voice patterns

### Amplitude

the height of a wave's crest
can be dramatically increased by resonance

### Rarefaction

a part in a longitudinal wave where the particles are spread apart

### Forced vibration

the vibration of an object that is made to vibrate by another vibrating object

### Wavelength

the distance (measured in the direction of propagation) between two points in the same phase in consecutive cycles of a wave

### Elasticity

the tendency of a body to return to its original shape after it has been stretched or compressed