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### Decibel scale

a logarithmic ratio scale that compares the amplitude and/or intensity of target sound to a standard reference sound; a logarithmis scale is used to measure intensity

### Inverse square relationship

intensity varies inversely with the distance from the source; intensity is decreased by the square of the distance change factor

### phon scale

a psychoacoustic scale for intensity that uses a 1000 Hz pure tone as the reference frequency; subjective scale for loudness

### psychoacoustics

study of the relationship between the phsycial properties of a stimulus and our subjective experience of the stimulus

### threshold of hearing

sound that a pair of normal human ears can detect 50% of the time under ideal listening conditions

### compression

area of positive pressure; collistions of air molecules result in regions of increased density

### constructive interference

waves that combine and increase the amplitude of the resulting wave; amplifies the rarefaction or an area of compression

### destructive interference

waves that combine and decrease the amplitude of the resulting wave; a wave interferes with another wave such that a compression of one wave meets a rarefaction of the other wave and the net effect is to decrease the overall energy

### refraction

the change in the speed and direction of a sounds wave due to inteaction iwith a boundary

### reflection

wave that collides with a surface and travels back toward the source; the sound wave bounces backward off the boundary

### reverberation

process generating a sound that last slightly longer due to interaction of incident and reflected waves

### standing wave

a pattern restulting from the interference of an incident and a reflected sound wave that apprears to be standing still

### amplitude

the amount of displacement of an object from its rest position; magnitude of oscillation or height of wave

### complex aperiodic sound

a sound wave consisting of multiple frequencies in which the cycles do not take the same amount of time to occur

### complex periodic sound

a sound wave consisting of multiple frequencies in which the cycles take the same amount of time to occur

### complex sound

sound with two or more frequencies; a sound wave consisting of two or more pure sounds

### fundamental frequency

lowest frequency of a complex periodic sound; the repetition frequency of a sine wave or a complex pattern

### harmonics

frequencies above F0 in a complex periodic sound, which are integer multiples of the fundamental frequency

### Quasiperiodic

a sound wave consisting of multiple frequencies in which the cycles do not take exactly the same amount of time to occue, but a repetitive pattern is apparent

### period

amount of itme consumed by each cycle in a wave; the reciprocal of the frequency, the duration of one cycle

### phase

relative timing of compressions and rarefactions of waves; the point in the cycle of cibration at which the waveform begins

### pure tone

sound with only one frequency; a sound wave consisting of energy at a single periodic frequency

### simple harmonic motion

a smooth back and forth movement with a characterstic pattern of acceleration though the rest position and deceleration at the end-points of the movement; unifrom ciruclar motion or perioidc motion around a central equilibrium point

### wavelength

distance covered by one complete cycle of a wave; distance covered by one cycle of vibration

### envelope

line that connects the frequencies of a complex sound represented on a spectrum; contour formed by the distplay of engery at each frequency represented in a sound wave

### fourier analysis

mathematical procedure to identify the individual sinusoids in a complex sound; a complex mathematical process of decomposing a complex wave into its separate sine waves; a method to transfer the time-series speech waveform into a frequency-based spectrum

### line spectrum

graph in which the frequencies in a complex periodic sound are depicted as vertical lines, where the height of the line indicates the amplitude of the compenent frequency

### power spectrum

a plot of the power (energy per unit of time) of given frequencies of a sound (same as a line spectrum)