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Physics Unit 7
Sound
| Term | Definition |
|---|---|
| sine curve | the waveform traced by simple harmonic motion, which can be made visible on a moving conveyor belt by a pendulum swinging at right angles above the moving belt |
| amplitude | for a wave or vibration, the maximum displacement on either side of the equilibrium (midpoint) position |
| wavelength | the distance between successive crests, troughs, or identical parts of a wave |
| frequency | for a vibrating body or medium, the number of vibrations per unit of time; for a wave, the number of crests that pass a particular point per unit of time |
| Hertz | the SI unit of frequency; one Hz equals one vibration per second |
| period | the time in which a vibration is completed; the period of a wave equals the period of the source & is equal to 1/frequency |
| transverse wave | a wave in which the medium vibrates perpendicularly to the direction in which the wave travels. (light waves & waves on stringed instruments) |
| longitudinal wave | a wave in which the medium vibrates parallel to the direction in which the wave travels (sound waves) |
| wave speed | the speed with which waves pass a particular point; wave speed=frequency X wavelength |
| wave interference | the phenomenon that occurs when two waves meet while traveling along the same medium |
| interference pattern | the pattern formed by the superposition of different sets of waves that produces reinforcement in some places & cancellation in others |
| standing wave | a stationary interference pattern formed in a medium when two sets of identical waves pass through the medium in opposite directions |
| Doppler effect | the shift in received frequency due to the motion of a vibrating source toward or away from a receiver |
| bow wave | the v-shaped disturbance created by an object moving across a liquid surface at a speed greater than the wave speed |
| shock wave | the cone-shaped disturbance created by an object moving at supersonic speed through a fluid |
| sonic boom | the loud sound that results from the incidence of a shock wave |
| pitch | the highness or lowness of a tone; related to wave frequency |
| infrasonic | describes a sound that has a frequency too low to be heard by humans |
| ultrasonic | describes a sound that has a frequency to high to be heard by humans |
| compression | a condensed region of the medium through which a longitudinal wave travels |
| rarefaction | a rarefied (of reduced pressure) region of the medium through which a longitudinal wave travels |
| reverberation | the persistence of sound, as in an echo, due to multiple reflections |
| refraction | the bending of sound or any wave caused by a difference in wave speeds |
| forced vibration | the setting up of vibrations in an object by a vibrating force |
| natural frequency | the frequency at which an elastic object tends to vibrate when it is disturbed & the disturbing force is removed |
| resonance | the response of a body when a forcing frequency matches its natural frequency |
| interference | a result of superposing different waves, often of the same wavelength; constructive is crest-to-crest; destructive is crest-to-trough |
| beats | a series of alternate reinforcements & cancellations produced by the interference of two waves of slightly different frequencies, heard as a throbbing effect in sound waves |
| intensity | the power per square meter carried by a sound wave, often measured in decibels |
| loudness | the physiological sensation directly related to sound intensity or volume |
| quality | the characteristic sound of a musical instrument or voice, which is governed by the number & relative intensities of partial tones |
| partial tone | a single-frequency component sound wave of a complex tone |
| fundamental frequency | the lowest frequency of vibration, or first harmonic, in a musical tone |
| harmonic | a partial tone whose frequency is an integer multiple of the fundamental frequency |
| Fourier analysis | a mathematical method that disassembles any periodic waveform into a combination of simple sine waves |