Sound Wave Properties and Acoustics

Vocabulary flashcards generated from lecture slides covering basic wave types, acoustic parameters, decibels, interference, harmonics, and sound envelope concepts.

Transverse Wave

A wave where the particle motion is vertical (up and down) while the motion of the wave is horizontal (left and right), such as a plucked guitar string.

Longitudinal Wave

A wave in which particles oscillate or vibrate in the same direction as the movement of the wave, such as sound traveling through air or water.

Sound Wave

Invisible patterns of energy that move through air, water, or solid objects by making tiny particles push back and forth.

Compression

An increase in atmospheric pressure where air particles are pushed close together.

Rarefaction

A decrease in atmospheric pressure where air particles are far apart.

Frequency

The main component of musical pitch, measured in cycles per second (cps) or Hertz ($\text{Hz}$), calculated as $F = \frac{1}{T}$ where $T$ is period in seconds.

Cycles Per Second (cps)

A measure of the frequency of a sound wave, representing how many times a wave vibrates back and forth in one second.

Hertz (Hz)

The standard unit of measurement for sound frequency, equivalent to cycles per second (cps).

Kilohertz (kHz)

A unit of frequency measurement equal to $1000\,\text{Hz}$ ($1000\,\text{Hz} = 1\,\text{kHz}$).

Pitch

How high or low a specific sound or note is perceived by the human ear, which operates in a nonlinear fashion.

Fundamental Frequency

The specific primary frequency that human hearing recognizes as the pitch of a sound.

Range of Human Hearing

The standard frequency bandwidth audible to the human ear, spanning from $20\,\text{Hz}$ to $20\,\text{kHz}$.

Bandwidth

A range of frequencies (also called a frequency band) defining the lowest and highest frequencies equipment or human ears can process or reproduce.

Octave

A frequency band representing a $2:1$ frequency relationship, created by a doubling of the fundamental frequency.

Low Bass

The frequency range encompassing the 1st and 2nd octaves, spanning from $20\,\text{Hz}$ to $80\,\text{Hz}$.

Upper Bass

The frequency range encompassing the 3rd and 4th octaves, spanning from $80\,\text{Hz}$ to $320\,\text{Hz}$.

Midrange

The frequency range encompassing the 5th, 6th, and 7th octaves, spanning from $320\,\text{Hz}$ to $2.5\,\text{kHz}$.

Upper Midrange

The frequency range encompassing the 8th octave, spanning from $2.5\,\text{kHz}$ to $5\,\text{kHz}$.

Treble

The frequency range encompassing the 9th and 10th octaves, spanning from $5\,\text{kHz}$ to $20\,\text{kHz}$.

Amplitude

The objective measurement of the degree of positive or negative change in atmospheric pressure caused by sound waves.

Decibel (dB)

A logarithmic scale used to express sound levels meaningfully in manageable numeric values.

Sound Pressure Level (dB-SPL)

A measure of physical sound wave loudness in the air using a decibel scale, where pressure increases exponentially relative to dB-SPL.

Environmental Decibel Levels

A scale categorizing relative sound pressure levels from quiet environments like $10\,\text{dB}$ up to severe noise levels like a jet plane at $135\,\text{dB}$.

Threshold of Hearing

The quietest sound pressure level detectable by the human ear, defined as $0\,\text{dB-SPL}$.

Threshold of Pain

The sound pressure level between $120\text{--}140\,\text{dB-SPL}$ (defined as $120\,\text{dB-SPL}$ in class), above which exposure causes pain, and past $150\,\text{dB-SPL}$ causes permanent damage.

Dynamic Range of Human Hearing

The $120\,\text{dB}$ difference between the quietest ($0\,\text{dB-SPL}$ Threshold of Hearing) and loudest ($120\,\text{dB-SPL}$ Threshold of Pain) audible sound levels.

Velocity of Sound

The speed of sound in air, which is approximately $1130\,\text{ft/s}$ ($770.5\,\text{mph}$ or $344\,\text{m/s}$) at average humidity and $70^\circ\text{F}$.

Wavelength

The physical distance required for a wave to complete one full cycle, calculated with the formula $\lambda = \frac{v}{f}$.

Period

The duration of time it takes for a sound wave to complete one cycle, reciprocal to frequency ($T = \frac{1}{F}$).

Acoustical Phase

The time relationship between two sound waves, measured in radial degrees ($360^\circ$).

Constructive Interference

Phase reinforcement occurring when two waves are in sync ($0^\circ$ or $360^\circ$ shift), resulting in increased total amplitude.

Phase Cancellation

Destructive interference caused by a $180^\circ$ phase shift between two waves, causing them to cancel out completely and yield no sound.

Comb Filter Effect

Phase interference caused by path length differences (time delays) between direct and reflected sound waves, combining constructive and destructive interference.

Sine Wave

A pure tone waveform containing no harmonics, serving as the fundamental building block of all sustained sound waves.

Triangle Wave

A waveform containing odd-numbered harmonics whose amplitudes are weighted by $\frac{1}{n^2}$.

Sawtooth Wave

A waveform containing all integer harmonics whose amplitudes are weighted by $\frac{1}{n}$.

Square Wave

A waveform containing odd-numbered harmonics (such as 3, 5, or 7) with amplitudes weighted by $\frac{1}{n}$.

Complex Aperiodic Wave

A non-repeating sound wave (such as white noise) that contains all frequency components.

Timbre

The distinct tone quality or color of a sound, shaped by the quantity and amplitude of its harmonic components.

Harmonics Calculations

The calculation of harmonic frequencies given by $f_h = f \times N$, where fundamental frequency $f$ is multiplied by harmonic number $N$.

Harmonic Distortion

Distortion produced by altering the shape of a sound wave, measured as a percentage of the original signal.

Inharmonic Overtone

An overtone partial frequency that is NOT an exact whole-number multiple of the fundamental frequency.

Sound Envelope

The internal dynamics of a sound showing amplitude changes over time, divided into four stages: Attack, Decay, Sustain, and Release (ADSR).

Attack (A)

The time it takes for a sound wave to rise to its peak amplitude.

Decay (D)

The time it takes for a sound wave to drop from peak amplitude to its sustain level.

Sustain (S)

The steady amplitude level maintained by a sound wave following its initial decay.

Release (R)

The time required for a sound wave to decrease from its sustain level to complete silence.