- a periodic wave whose waveform (shape) is the trigonometric sine function - a single frequency with no harmonics - considered an acoustically pure tone

Acoustics II Test Flashcards by Laura Nickel

Oscillation

repetitive or periodic variation, typically in time, of a wave about a central value or between two or more different states

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Cycle

the time between a point on a wave and the same point on the next iteration of the wave

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Frequency

the number of wave cycles that pass by each second, and is measured in Hertz (Hz)

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Frequency range of human hearing

20Hz to 20,000 Hz

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Infrasonic Sound

sounds below human hearing range

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Ultrasonic Sound

sounds beyond human hearing range

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Sine Wave

a periodic wave whose waveform (shape) is the trigonometric sine function
a single frequency with no harmonics
considered an acoustically pure tone

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Resonance

Frequency/Speed at which something naturally vibrates

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Sympathetic Vibration

vibration of sound & resonance from a source that causes other objects/instruments to resonate in the same room without being physically played
- pianos, drums, sitars, etc

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Just Intonation

tuning intervals as whole number ratios of frequencies

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Equal Temperament Tuning

approximates just intervals by dividing an octave into steps such that the ratio of the frequencies of any adjacent pair of notes is the same
- stretched tuning

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A 440

A4 (above middle C)
Concert Pitch for orchestras

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Scales

major, minor, modal
western v. eastern music
(microtonal)

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Intervals

the distance between two notes

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Spectrum of pitch perception

Amusia - tone deaf
Relative Pitch
Absolute/Perfect Pitch

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Consonance

together/with

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Dissonance

clashy/unpleasant/unresolved

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Unison

Same Pitch

Beats

near unison but slight phasing issues, sound cuts in and out

Harmonic Series

Fundamental: starting pitch
Partials: all frequencies that make up a sound
Overtone: partials that are whole number multiples of the fundamental (harmonics) (pitched or unpitched)

Timbre

tone quality
balance between frequencies

Frequency Masking

sounds that cover up other sounds, esp in the same freq range

Noise

random sounds

Harmonic sound

pitched sound

Frequency response

measure of how something affects the timbre of the sound

Fletcher-Munson Curves

a set of experimentally determined graphs that show how loud—in dB SPL—a sound at one frequency must be to be perceived as equally loud as a sound at another frequency

Bandwidth (Q)

the width of frequencies being manipulated in an EQ - Q control can narrow or widen this curve

Wavelength

the length of the wave measured in feet Bass - long wavelength Treble - short wavelength

Wavelength equation

Wavelength = (speed of sound)/frequency

Speed of sound

1125 feet per second

Audio Filters

LPF: Low Pass Filter HPF: High Pass Filter Band Reject: cuts out a band Notch: narrow band reject Resonant: emphasize/ suppress the harmonics of a frequency

Shelving (EQ)

move up/down desired freq and all above/below point

Peak/Bell (EQ)

cutting/boosting a chosen freq and those surrounding it, determined by Q

Boost or cut (EQ)

amplify or attenuate a frequency

Sweep or switchable (EQ)

Sweep - fine tuning and smooth EQ controls Switchable - set points on EQ predetermined by manufacturer

Active or passive (EQ)

Active: needs power to operate, good isolation, signal boost w/amps Passive: no noise, reduces signal, high dynamic range

Exciters & psychoacoustic processors

- add harmonic distortion - change phase - add/subtract bass

Pitch Processors

harmonizers/pitch shifters, Auto-Tune, Melodyne

Subharmonic Synth/Bass Synth

generates lower octaves

Wavelength

physical length of a wave measures in feet/inches/meters

Frequency

waves per unit of time (second) Cycles per second = Hertz (Hz/kHz)

Period (1/f)

how much time for a cycle measured in seconds/milliseconds per cycle

Speed of sound

Velocity of wave through a medium 767 miles per hour 1125 feet per second