CDO 463 1 Basic Acoustics

sensation for hearing

physical quantity with vibration - periodic or aperiodic - and a pressure disturbance - compressions and rarefractions - and a medium - material for transmitting the sound

• regularly repeating
• ex) tone
• repeats the same frequency

• not reguarly repeating
• 2 types - turbulent and static
• ex) noise, bullistic, release of stop consonants

• produces the simpliest type of sound
• tine movement : X-Y-X-Z-X-Y-X-Z-X
• one cycle: X-Y-X-Z-X

• amount of time for one cycle / # cycles per second
• frequency = 1/period or f=1/T
• physical dimension - observable and measurable
• Hz

the perception of frequency

• increase in frequency = increase in pitch
• not a 1:1 change/dimension
• same physical change does not equal the same perceptual change

• force or pressure of sound
• related to displacement of tine

• perception of amplitude
• decibel dB

• increase in amplitude = increase in loudness
• not a 1:1 dimension

• another type of SHM
• circle of radius r
• point P moves around circle at a uniform speed
• at each new P, a new radius r' is drawn that forms an angle (theta) with the original r
• by the time P goes around the circle, theta will go from 0 to 360 degrees

the angle of theta

time for one revolution

# cycles/second

the radius of the circle

• the sine of theta
• X = r * sine

• graph of displacement as a function of time
• the waveform associated with SHM is the sine wave because the formula contains the sine function

• time
• amplitude
• frequency

• amplitude
• frequency

• velocity is zero / movement stops at the extremes
• velcoity is at its max at the point of rest

the amplitude graph is alays 90 degrees behind the velocity graph

• adding sine waves together
• go point by point on the x axis and add the y axis numbers together

• a sine wave with the same frequency
• creates simple waves

• complex waves - any wave that is not a sine wave
• a wave with more than one frequency component

adding the odd multiples of a given frequency

• the lowest frequency
• largest comon multiple in a series of frequencies

frequencies that are integer multiples of the fundamental frequency