2.3 Physics

Sound

any vibration that pushes and pulls molecules in a medium that it travels through which causes different densities which are interpreted by the brain

Through what type of wave does sound travel?

longitudinal waves

How does sound from audio displays travel?

transverse waves

What influences pitch?

wavelength and frequency

What wave property influences volume?

amplitude

What does interference affect in sound?

volume

In-Phase Interference

crest to crest and trough to trough alignment

Out-of-Phase Interference

no crest to crest and trough to trough alignment

Completely Out of Phase

special case of out of phase where crests line up with troughs

Constructive Interference

amplitudes add together when waves meet with sound waves which produces a louder volume/sound

Destructive Interference

amplitudes subtract when waves meet with sound waves which produces a quieter or no volume sound

Combined (Destructive + Constructive) Interference

amplitudes subtract and add together when waves meet, peaks in the same direction add together and peaks in opposite directions subtract from one another

What does combined interference cause?

beats

Doppler Effect

a moving source of sound will sound higher pitched to me when it is moving towards me, because I encounter the sound waves more frequently.

a moving source of sound will sound lower-pitched to me when it is moving away from me, because I encounter the sound waves less frequently.

When a wave move towards you, the wave…

compresses so it has shorter wavelength and higher frequency

When a wave is moving away from you the wave…

expands so it has larger wavelength and lower frequency