Sound

Sound

Increases and decreases in the pressure of a medium propagated from a vibrating source to the ear

Static pressure

The pressure of a still medium

Frequency

Cycles of pressure variation in a second at a single point in space

Period

Seconds in a cycle of pressure variation at a single point in space

Wavelength

Distance of a cycle of pressure variation at a single point in time

Speed

Property of sound determined by the density and stiffness of the medium

Simple harmonic motion

Sinusoid pressure variations represented by the equation x(t)=A(sin(2πft+Φ)

Intensity

Power over space

Inverse squares law

I=1/(d/d_ref)²

Decibels from pressure

20log(p/p_ref)

Decibels from intensity

10log(I/I_ref)

Intensity to pressure

I/I_ref=(p/p_ref)²

p_ref of dB SPL

0.00002 N/m²

I_ref of dB SPL

10^-12 W/m²

2x intensity (different tones)

+3 dB

2x intensity (same tone)

+6 dB

2x distance from source

-6 dB

Click

A short, broad-frequency noise

Spectral splatter

Click at the beginning and end of a pure tone starting and stopping abruptly

Rectangular window

Abrupt amplitude change in tone onset and offset

Hanning window

Gradual amplitude change in tone onset and offset

Time/frequency tradeoff

Wide spectral content can be recorded within a short length of time, while narrow spectral content can be recorded with a long length of time

Complex tone

Non-sinusoidal tone that repeats at the period of the fundamental frequency and includes harmonics at multiples of that frequency

Timbre

Harmonic profile of a sound source

White noise

Noise with a random assortment of frequencies and phase

Low-pass noise

Noise cut off above a certain frequency

Band-pass noise

Noise centering at a particular frequency and filtering out frequencies too far from that frequency

High-pass noise

Noise cut off below a certain frequency

Low-pass noise

Noise filtering out frequencies above a certain cutoff

Carrier

The fine structure of an amplitude modulated tone

Envelope

The gross structure of an amplitude modulated tone

Amplitude modulation

Modulation of a carrier frequency through the wave height

Frequency modulation

Modulation of a carrier frequency through the wave speed

Resonance

Natural vibration frequency of an object

DC component

Energy at 0 Hz generated from asymmetrical sound pressure

Amplitude spectrum

Standard frequency spectrum

String vibration

Vibration with a resonant frequency related to mass and tension and harmonic frequencies at amplitudes related to the point of force

Nodes

Points of zero pressure in a sound wave

Standing waves

Waves that change over time, but not space, created by reflection of soundwaves

Spectrum level in dB

Total pressure - bandwidth

Hz of tone f, n octaves higher

f(2ⁿ)

Hz of tone f, n octaves lower

f/2ⁿ

Equivalent rectangular bandwidth

Bandwidth of a rectangular filter with the same peak, center, and intensity as a non-rectangular filter

Impulse response

Waveform produced when an impulse is passed through a filter

Analog-to-digital converter

Series of pressure values recorded at regular intervals and stored as digital values