Sound and Its Measurement – Key Vocabulary

A comprehensive set of vocabulary flashcards covering fundamental acoustic and audiologic terms from Chapter 2, “Sound and Its Measurement,” in Introduction to Audiology (13th ed.).

Sound

Vibrations of molecules that propagate through a medium as pressure waves.

Elasticity

The springiness of a material; closer molecular spacing produces higher elasticity, as in solids.

Brownian Motion

Rapid, random movement of air particles that increases with heat.

Compression

Region in a longitudinal wave where particles are pushed closest together.

Rarefaction

Region in a longitudinal wave where particles are spread farthest apart.

Transverse Wave

Wave in which particle movement is perpendicular to wave propagation (e.g., guitar string, light).

Longitudinal Wave

Wave in which particle movement is parallel to wave propagation; sound waves are longitudinal.

Sine Wave

Fundamental graphical representation of sound showing one periodic cycle of compression and rarefaction.

Pure Tone

Sound containing only one frequency of vibration, represented by a single sine wave.

Vibration

Mechanical oscillation or repetitive back-and-forth movement of a mass.

Frequency

Number of cycles of vibration per second, measured in hertz (Hz).

Period

Time required to complete one full cycle of vibration.

Amplitude

Height of a waveform indicating how far a mass moves; correlates with sound intensity.

Resonant Frequency

Natural rate at which a mass vibrates most easily and with greatest magnitude.

Sound Velocity

Speed at which a sound wave travels; increases with medium density, temperature, and humidity.

Wavelength

Distance between identical points on consecutive cycles of a wave; inversely proportional to frequency.

Interference

Interaction of multiple sound waves that can reinforce or cancel amplitude depending on frequency, intensity, and phase.

Beats

Periodic loudness fluctuations heard when two tones of nearly equal frequency are presented together.

Complex Sound

Sound composed of several sine waves at different frequencies and intensities; speech is an example.

Fourier Analysis

Mathematical breakdown of a complex wave into its individual sinusoidal components.

Fundamental Frequency

Lowest frequency component present in a complex sound.

Harmonic

Whole-number multiple of a fundamental frequency in a periodic complex wave.

Formant

Peak in the speech spectrum created by vocal-tract resonance.

Intensity

Amount of acoustic energy per unit area; perceived as loudness and decreases with the square of distance.

Force

Push or pull that initiates vibration, measured in newtons (N).

Pressure

Force per unit area, measured in pascals (Pa).

Work

Energy expended when a mass is moved; force multiplied by distance, measured in joules (J).

Power

Rate at which work is done or energy is expended, measured in watts.

Impedance

Opposition a medium offers to sound transmission, measured in ohms (Ω).

Resistance

Frequency-independent component of impedance that dissipates acoustic energy.

Reactance

Frequency-dependent component of impedance produced by mass and stiffness.

Mass Reactance

Portion of reactance that increases with the mass of the system and with frequency.

Stiffness Reactance

Portion of reactance that decreases as frequency increases and relates to system elasticity.

Decibel (dB)

Logarithmic unit expressing the ratio between a measured sound and a reference level.

dB IL

Decibel scale referenced to sound intensity level.

dB SPL

Decibel scale referenced to sound pressure level; used for calibration and physical measurements.

dB HL

Decibel scale referenced to average normal hearing thresholds; 0 dB HL is audiometric zero.

dB SL

Decibel value expressed relative to an individual’s own hearing threshold at a specific frequency.

Audiometric Zero

Lowest sound intensity that stimulates normal hearing, defined as 0 dB HL.

Physical Acoustics

Study of sound as a physical phenomenon, independent of human perception.

Psychoacoustics

Study of relationships between acoustic stimuli and psychological responses.

Pitch

Perceptual correlate of frequency; higher frequencies are perceived as higher pitch.

Loudness

Perceptual correlate of intensity, influenced by both intensity and frequency.

Localization

Ability to determine the direction of a sound source using interaural intensity and phase cues.

Masking

Elevation of hearing threshold for one sound caused by the presence of another sound (the masker).

Diagnostic Audiometer

Instrument that measures hearing sensitivity via air, bone, and speech testing with multiple transducers.

Pure-Tone Audiometer

Device primarily for screening that presents only pure-tone stimuli via air and bone conduction.

Speech Audiometer

Audiometer capable of presenting both pure tones and speech materials for clinical diagnosis.

Sound Level Meter

Handheld device with microphone that measures ambient sound pressure levels in decibels.

A-Weighting

Frequency weighting filter approximating human ear sensitivity; used for OSHA noise-risk assessment.

C-Weighting

Frequency weighting that measures sound uniformly from 30–10,000 Hz; useful for high-level or low-frequency noise.

Maximum Permissible Ambient Noise

ANSI-specified sound pressure limits that audiometric test rooms must not exceed.

Coupler

Device that connects earphones or insert receivers to a sound level meter during calibration.

Artificial Mastoid

Coupler simulating skull properties used to calibrate bone-conduction vibrators with a sound level meter.