Kinds of Sound
Sound travels as this kind of wave.
Longitudinal
About how fast sound travels in air.
340 m/s
The change in frequency when a source moves toward or away from you.
The Doppler effect
The lowest frequency that can resonate on a string.
Fundamental frequency
Two close pitches produce this "wah-wah" pulsing.
A beat
Crowded-together regions in a sound wave.
Compressions
Sound’s speed depends on this.
The medium
If a source moves toward you, the frequency you hear does this.
Increases
When a driving frequency matches the natural frequency and amplitude grows.
Resonance
Two waves that add crest-on-crest are this.
In phase
Spread-apart regions in a sound wave.
Rarefactions
Of solid, liquid, and gas, sound is usually fastest here.
A solid
Loudness is measured in these units.
Decibels
The mix of harmonics that gives a note its quality.
Timbre
Two waves that cancel crest-on-trough are this.
Out of phase
A sound higher than 20,000 Hz.
Ultrasonic
A stiff medium does this for the next wave.
Rebounds easily
The threshold of hearing is given this decibel value.
0 dB
A pipe closed at one end supports only these harmonics.
Odd harmonics
The thin membrane that turns air vibrations into mechanical motion.
The eardrum
The everyday name for a sound’s frequency.
Pitch
A medium that is not stiff tends to do this to the wave.
Absorb it
For light, a source moving away produces this shift.
A redshift
A non-fundamental harmonic sounding with the fundamental.
An overtone
The coiled structure that turns vibration into nerve signals.
The cochlea