375 Sound Basics: The Physical Stimulus

sound travels in

waves

compression

increase in amplitude

rarefaction

decrease in amplitude

frequency

peak of

loudness

subjective perception of how loud or soft a sound is

physical loudness

amplitude

unit of loudness

dB, changes in air pressure

pitch

how high or low a sound is, wavelength

unit of pitch

Hz, number of cycles per second

dog frequency range

60-45k Hz

bat frequency range

3k-120k Hz

phase

where a peak, trough, rarefaction occurs, position of sound wave in a cycle

counterphased

when a peak of one wave is lined up with the trough of another, wave is offset by 180 degrees, results in silence or reduced sound

noise cancellation

a sound combined with its counterphase

speed of sound

1115 ft/s, faster in solids

echo

sound reflected off a surface is delayed, about a 35ms difference

fundamental frequency

the lowest frequency of a periodic waveform, aka the first harmonic

Fourier analysis

our ears break down each sound wave so we can perceive it

square wave

made of a fundamental frequency and numerous harmonics

Ohm’s law

our auditory system acts as a form of frequency/Fourier analysis so we can perceive sounds, allows us to differentiate between sounds

timbre

perceptual ability of judging two sounds that have the same loudness and pitch as different

example of timbre

different instruments, we can distinguish

when analyzing timbre

frequency and loudness are matched but we are able to differentiate between different sounds and their sources