SOUND, SPEECH, HEARING

wave

travelling disturbance carrying energy from place to place

longitudinal wave

disturbance parallel to direction of travel of wave

example of longitudinal wave

sound

transverse wave

disturbance perpendicular to direction of travel of wave

example of transverse wave

guitar, banjo

periodic waves

cycles produced over and over again by source

simple harmonic motion

repetitive movement back and forth through central position/equilibrium, displacement on one side = maximum displacement on other side

amplitude

maximum excursion of particle of medium from

period

time required to complete 1 cycle

what does speed of wave on string depend on

speed of particle in string accelerates (upward) in response to net force

where cant sound exist

vacuum

distance between adjacent condensations equal to

wavelength of sound wave

where do compressions and rarefactions travel

speaker to listener, but air molecules dont move with wave

how is vibration interpreted by brain

wave arrives at ear, condensations and rarefactions force eardrum to vibrate at same frequency as speaker

pure tone

sound w single frequency

pitch

frequency interpreted by brain

loudness depends on

pressure amplitude of wave

power of wave

energy transported per second by wave

sound intensity

power perpendicular through surface/area of surface

threshold of hearing

intensity of sound human ear can detect

exposure to intensity greater than 1 W/m^2

painful

what if sound emits uniformly in all directions

intensity depends on distance from source simply

decibels

measurement used when comparing 2 sound intensities

intensity level is what type of scale

logarithmic scale

doppler effect

change in frequency/pitch detected by observer die to difference in velocities from source and observer

compression

• particles pushed together

• high pressure, high density

‘dense’

rarefaction

• particles spread apart in wave

• low pressure, low density

‘rare’ (few)