Lecture Notes: Acoustics & Audiometry — Vocabulary Flashcards

A set of vocabulary flashcards covering key terms related to amplitude, decibels, frequency, wave types, sound taxonomy, audiometry, and psychoacoustics as presented in the notes.

Amplitude

The magnitude of displacement of a wave from its equilibrium; related to energy and the perceptual loudness; in audiometric tasks, amplitude is the parameter that is varied; unit associated with loudness is the decibel (dB).

Loudness

The perceptual correlate of amplitude; the subjective sense of how loud a sound seems.

Decibel (dB)

A nonlinear logarithmic unit used to express ratios between physical magnitudes (e.g., sound pressure or intensity); compresses large ranges into a manageable scale; named after Alexander Graham Bell.

dB SPL (Sound Pressure Level)

Decibel scale for sound pressure relative to a reference pressure (20 µPa); 0 dB SPL corresponds to the threshold of hearing; used to quantify actual sound pressure.

dB HL (Hearing Level)

Audiometric decibels referenced to ANSI standards; 0 dB HL is the average threshold of normal hearing, used to describe hearing loss.

Infrasound

Very low-frequency sounds below approximately 20 Hz that are generally inaudible to humans.

Audible sound

Sounds within the typical human hearing range (roughly 20 Hz to 20 kHz) that can be heard.

Ultrasound

Very high-frequency sounds above approximately 20 kHz that are inaudible to humans.

Frequency

The number of cycles per second of a periodic waveform, measured in Hz; determines pitch.

Longitudinal waves

Waves in which particle displacement is parallel to the direction of energy transfer; in air, these include sound waves with compressions and rarefactions.

Compression

Regions of higher pressure in a longitudinal wave.

Rarefaction

Regions of lower pressure in a longitudinal wave.

Tones (Periodic Sounds)

Sounds produced by periodic vibrations; include pure tones and complex tones.

Pure tone

A sound with a single frequency component.

Complex tone

A sound with more than one frequency component.

Noises (Aperiodic Sounds)

Sounds without a repeating waveform; energy spread across frequencies and time; can be stationary or nonstationary.

Continuous noise

Noise with energy across frequencies that is sustained over time.

Impulse noise

A single brief event with a large peak and short duration (e.g., clap, slam, blast).

Stationary noise

Noise whose statistical properties do not vary over time.

Nonstationary noise

Noise whose properties change over time.

Absolute threshold

The minimum stimulus intensity detectable 50% of the time.

Detection

The ability to perceive a stimulus; the minimal perception of presence of a stimulus.

Discrimination

The ability to notice differences between stimuli (e.g., in frequency or intensity).

Scaling

The process of ascribing a numerical magnitude to the perceived intensity of a stimulus.

Fechner

Gustav Fechner, founder of psychophysics; developed methods to measure detection, discrimination, scaling, and absolute threshold.

Audiometer

Device that generates and controls acoustic test signals (frequency, amplitude, duration) for audiometric testing.

Audiogram

Graph plotting a listener’s hearing thresholds (in dB HL) across frequencies.

Pure Tone Audiogram

An audiogram showing thresholds for pure-tone stimuli (single-frequency tones).

SRT (Speech Reception Threshold)

The minimum hearing level at which speech can be understood or recognized.

Word recognition

The ability to identify spoken words at a given intelligibility level.

Range of Human Hearing

Typically 20 Hz to 20 kHz; sensitivity is greatest between 500 Hz and 4,000 Hz; thresholds described in dB HL.

Most sensitive frequency range

The 500–4000 Hz band where human hearing is most acute.

Reference Level

A baseline or zero point established for measurements (e.g., classroom reference level to set a new zero).

Auditory signal

A signal intended to be heard by the listener during testing or stimulation.