Music Acoustics

any form of to-and-fro motion, aka oscillation

A perceived, aural psychological sensation produced by vibration

graph of the simplest form of vibration showing motion in time and space

the sound produced by sinusoidal vibration or oscillation; also known as a pure tone

simple vibration; motion that takes place in a straight line and is periodic

Natural tendency of a displaced body to return to its point of rest

tendency of a displaced body to overshoot its point of rest

number of cycles (complete vibrations) which take place in one second; also the # of sound waves passing a given point in one second

frequency at which a body tends to vibrate due to its natural characteristics of size, shape, molecular composition, and the stress it is under

Material, whether or not it is under stress, and its proportions. Ex: string: length and thickness, tension, material of string

Our perception of frequency (an aural sensation).  Greater the frequency, the higher the perceived pitch. Rate of vibration is pitch

distance thru which a vibrating body moves; aka amount of displacement of a vibrating body

perception of amplitude.  greater the amp, the louder it is perceived; also depends on where the fre/am of material vibrating lies w/in limits of human hearing

Inability to perceive certain frequencies and amplitudes which are within the common limits of perception

No lower than 20Hz and no higher than 20,000 Hz

as we get older: upper limit 10,000 Hz

One hundredth of a chromatic semitone; unit most used to represent pitch deviation

• Unit of sound intensity; relationship bt sound being measured and a reference intensity upon which the sound level meter is calibrate
• Is approx smallest change in intensity the human ear can detect

120 dB

transmitter of vibration from a sound source to a receiver; must be plastic in order for vibration to take place

point in space where a number of molecules which have been set into motion in effect bunch up causing an unusual number of molecules to occupy the same space

point at which usual number of molecules which occupy a given space are temporarily out of position, causing a partial vacuum to occur

bouncing back of sound waves as they strike a surface more dense than that in which they are traveling

sound waves which have been reflected; do not disturb the frequency of other wavefronts

1100 ft per second, aka 4.7 seconds for 1 mile

transmission of vibration from one body to another, usually through the air.  aka sympathetic vibration; fre of 1st body must be exactly or very near the nat'l frequency of 2nd body

excitation of a second sound source

sensory characteristic determined mainly by the degree of complexity of the vibration of a body

frequency at which the sound source vibrates as a whole; also expressed as the lowest pitch that the sound source is capable of producing

one of the frequencies produced by the complex vibration of a body; is a whole number multiple of the fundamental

a series of tones (overtones) caused by the complex vibration of a body; fundamental frequency referred to as the 1st harmonic

any component of the harmonic series including the fundamental.  often the terms o,h, and p are used interchangeably

Frequencies which are more resonant than others

the temporal shape of a tone consisting of an attack, initial decay, sustain, and final decay

frequency, amplitude, timbre, and envelope

complex sounds which are aperiodic and contain overtones which are not part of the nat'l harmonic series

Those frequencies above a fundamental tone which are not a whole-number multiple of the fundamental; have inconsistencies of tension, tress, and configuration

random occurrence of all pitches at equal amplitude within the audible frequency spectrum

composite of sound in a particular environment; all sounds present except the sounds you are trying to attend to

process by which the threshold of audibility of one set of sounds is raised by the present of another set of sounds; amt of masking effect usually expressed in dB

regular and repeated excitation of energy traveling back and forth gives appearance that the wave is standing still; have loops and nodes

• waves in which the molecules of the transmitting medium were disturbed at right angles to the sound source
• ex: tuning fork

• molecules of transmitting medium are disturbed in the same direction as the sound source
• ex: coiled spring in cylinder; hit at one end and spring moves back & forth (see - slinky)

Sound source is stretched, vibrating string over a resonating air chamber; 2 categories: length of string changed w/fingers and strings of fixed length

tones produced on stringed instruments by lightly touching a point along the string's length as it is bowed where a node exists

suppression of vibration by applying physical restraint

to-and-fro movement in a twisting direction; creates more complex vibrations

Metal inlays in the fingerboard of some stringed instruments that fix length of the string when the finger presses behind them

uses reed or edge tone to produce periodic puffs of air and resonate a column of air

• vibes caused by eddies (vortices) of air which are produced by a stream of air blown across the edge of a plate
• low intensity and high frequency
• wave 2x long as pipe

• any object or pair of objects which, when vibrated at the closed end of a pipe, sets the air in the pipe into vibration
• longitudinal and transverse vibrations

Size (diameter) of the inside of a pipe

windpipe or tube from the lungs to the throat and mouth; vocal folds lie at top and across of trachea forming the glottis

Opening bt the vocal folds

sound source of either vibrating membranes or vibrating solid bodies; inharmonic overtones

...Membranes stretched over a frame which are struck

Acoustic pictures that show where the loops and nodes are located on the stretched membrane

speed at which sound travels... at 68 d F, 1130 fps; 32 travels at 1088

• shape or configurations of the component compressions and rarefactions as they diffuse through a medium
• leave at speed of sound over ever-widening area

dissipation of sound energy or weakening of wave trains as they travel thru a medium

1000-5000 Hz

bending of wave fronts as they pass through mediums having unequal or varying density

spreading out of wave fronts into areas behind and around physical barriers; filling-in of areas or spaces behind physical barriers that are blocks and not in a straight line from the sound source

When there is more than one sound source present

Periodic reinforcement and cancellation of two wave fronts with frequencies closer together than 20 Hz

do not exist in environment, but by forcing parts of the air into non-linear vibration, are created w/in the ear itself

periodic reinforcement and cancellation of two wave trains with the frequency further apart than 20Hz may be perceived as a 3rd tone whose frequency is the difference bt the frequencies of the original tones

subjective tones produced by the ear that are perceived as the sum of 2 external frequencies

perceived phenomenon of multiple echoes mixing with the primary sound

trapping of sound waves in fibrous or porous materials which weakens the wavefront by reflecting and diffusing sound energy

preventing sound waves from traveling thru physical barriers thru combinations of reflection,absorption,diffusion, or creating a barrier

Thin membrane or disk that receives and transmits transverse acoustic vibrations

degree of accuracy of reproduction of an acoustical phenomenon replicated by an electrical sound system, both in amp and fre

any material that easily allows electric current to pass thru it

rate of flow of electricity

complete path of an electric current, usually including the generator

transducer of mechanical energy into electrical energy

force which surrounds magnets; circulation of electrons that constantly moves thru a magnet creating a field of force