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Intro to Aud. Ch 3
Sound and its measurement
| Term | Definition | extra info |
|---|---|---|
| Sound | A stimulus that has the capability to produce an audible sensation | Sound may be defined as a psychological or physical phenomena |
| stimulus | An oscillation or vibration in a medium | |
| Components of sound | There has to be an ENERGY SOURCE, an OBJECT capable of vibration, a MEDIUM, and a RECEPTOR (occurs in the psychological definition only) | |
| Sound-Energy source | produces the sound | ex: you can't just hold a tuning fork, you have to apply energy or force to make it vibrate |
| Sound-object | the object has to be capable of vibration | ex: tuning fork, guitar string |
| sound-medium | how we transmit the vibration to the ear | air is a medium because the molecules are moving, the skull can be a medium because it moves when the fork touches it, water can also be a medium |
| vibration | when an object is at a point of rest then moves from the point of disturbance striking and bouncing off adjacent molecules | |
| Sound-receptor | someone capable of hearing the sound | |
| Simple harmonic motion | The simplest pattern of vibration | |
| pure tone | a tone of only one frequency (no harmonics) | seldom appear in nature, usually created by devices like tuning forks or electronic sine wave generators |
| sinusoid(al) or sine waves | the waveform of a pure tone showing simple harmonic motion | |
| waveform | a vibrating pattern that presents a smooth wave | made up of frequency and period |
| one cycle | movement from equilibrium to maximum displacement in one direction, back to equilibrium, on to maximum displacement in the opposite direction and then back to equilibrium | |
| oscillation | the back and forth movement of a vibrating body | |
| frequency | the number of complete oscillations (cycles) of a vibrating body in a 1 sec period of time | frequency is displayed in Hertz (Hz) or cycles per sec (cps) |
| Period | amount of time it takes to complete 1 vibration of a cycle | ex: if frequency is 3Hz the period (T) equals 1/3 sec |
| amplitude | distance a vibrating object moves from its point of rest | the louder the sound, the greater the amplitude |
| amplitude is correlated with | loudness | |
| frequency is correlated with | pitch | |
| cancellation | reduction in amplitude to zero because of interaction of two tones 180 degrees out of phase | the reduction of the amplitude of a sound wave to zero |
| complex sound | energy at a number of different frequencies, amplitudes, and phase relationships | composed of two or more pure tones comprised of periodic or aperiodic waves |
| Fourier analysis | any complex wave can be decomposed to determine the amplitudes, frequencies and phases of the sinusoidal components | sound waves can be classified by its reference to periodicity and complexity |
| periodic wave | a waveform that repeats itself over time | a musical note is always the same so it is a periodic sound |
| aperiodic waves | a wave that lacks periodicity, no repetition, vibratory motion is random, usually perceived as noise | the sound "sh" is random, not repeatable |
| fundamental frequency | the lowest rate of a sound's vibration | determined by the physical properties of the vibrating body |
| harmonics (overtones) | any whole number multiple of the fundamental frequency of a complex wave | each sinusoid in the series must be an integer multiple of the lowest in the series. ex: if lowest=100Hz, components are 100, 200, 300, 400, 500 etc |
| Phase | the relationship in time between two or more waves | |
| starting phase | the angle in degrees at the moment rotation begins | note: wave travels counter clockwise from 0°-360° |
| resonance | the ability of a mass to vibrate at a particular frequency with least external force | |
| watt | a unit of power | |
| exponent | a logarithm | |
| intensity | the amount of energy per unit of area | |
| velocity | the speed of a sound wave in a given direction | |
| wave | a series of moving impulses set up by a vibration | |
| dyne | a unit of force just sufficient to accelerate a mass of 1 gram at 1 cm per second squared | |
| fourier | analysis that breaks a wave into its components | |
| erg | unit of work | |
| cycle | complete sequence of events of a sine wave through 360 degrees | |
| decibel | ratio between two sound pressures or two sound powers | |
| pressure formula | dynes/cm2 | |
| just audible sound | .0002 dynes/cm2 | |
| loudest audible sound | 2000 dynes/cm2 | |
| Acoustics | The nature of sound and how it's measured | The foundation for the testing of hearing. |
Created by:
schaunag
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