Audio Glossary - Sound & Frequency Terms Explained

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A440 (concert pitch): The international tuning standard: the A above middle C at 440 Hz, codified as ISO 16. Every instrument tuned to it agrees with every other. Hear A440 →
Amplitude: The size of a sound wave's pressure swing - the physical quantity behind loudness. In digital audio it is expressed relative to full scale (dBFS).

Binaural beats: A perceived pulsing created by playing slightly different frequencies to each ear; the brain constructs a beat at the difference frequency. Requires headphones. Binaural beats generator →
BPM (beats per minute): Tempo: how many beats fit in one minute. 60 BPM is one beat per second; one beat lasts 60,000 ÷ BPM milliseconds. BPM to ms calculator →

Cent: One hundredth of a semitone - the standard unit for tuning error. Differences under ~5 cents are hard to hear; 100 cents is a full semitone. Note ↔ frequency converter →
Crossover: The frequency at which an audio system hands off between drivers - e.g. sending everything below 80 Hz to a subwoofer and the rest to the main speakers. Subwoofer test →

dBFS: Decibels relative to digital full scale. The loudest representable sample is 0 dBFS; every real signal is negative. A peak measure, not a loudness measure.
dBu / dBV: Absolute voltage levels: dBV referenced to 1 V, dBu to 0.7746 V. Pro line level is +4 dBu; consumer line level is −10 dBV. dB converter →
Decibel (dB): A logarithmic ratio unit used throughout audio. +6 dB doubles voltage, +3 dB doubles power, and roughly +10 dB doubles perceived loudness. dB converter →

Equal temperament: The modern tuning system dividing the octave into 12 equal ratios of 2^(1/12), letting every key sound equally in (and equally slightly out of) tune.

Frequency: How many times per second a wave repeats, measured in hertz. Higher frequency = higher pitch. Human hearing spans roughly 20 Hz to 20,000 Hz. Tone generator →
Frequency response: How evenly a device reproduces different frequencies, usually shown as a curve. A flat response reproduces all frequencies at equal level. Sweep generator →
Fundamental: The lowest frequency component of a musical sound - the one that names its pitch. Everything above it is harmonics.

Harmonics (overtones): Frequency components at whole-number multiples of the fundamental. Their relative strengths create timbre - why a violin and flute playing the same note sound different. Waveforms guide →
Headroom: The margin between a signal's peak and the maximum the system can pass without clipping. Digital masters typically leave at least 1 dB of true-peak headroom.
Hertz (Hz): The unit of frequency: cycles per second. Named after Heinrich Hertz. 1 kHz = 1,000 Hz.

Interval: The pitch distance between two notes, named by scale steps (minor third, perfect fifth). Recognizing intervals by ear is the core of relative pitch. Interval trainer →

Latency: The delay between an audio signal being sent and heard. Bluetooth adds 40-300 ms depending on codec; wired audio is near-instant. Latency test →
LFE: Low-Frequency Effects - the ".1" channel in surround sound, band-limited to roughly 20-120 Hz and reproduced by the subwoofer. Surround sound test →
LUFS: Loudness Units relative to Full Scale - standardized perceived loudness, measured with ear-weighted filtering over time. What streaming platforms normalize on. Streaming loudness guide →

Masking: One sound making another inaudible. Steady broadband noise masks unpredictable sounds - the mechanism behind every sleep-noise machine. White noise →

Noise colors: Broadband noise named by spectral tilt: white (flat), pink (−3 dB/octave), brown (−6 dB/octave), plus descriptive colors like green (mid-band) and gray (equal-loudness). Noise generator →

Octave: The interval between a frequency and its double. 220 Hz, 440 Hz, and 880 Hz are the same note (A) in adjacent octaves.
Oscillator: A circuit or algorithm producing a repeating waveform at a set frequency - the sound source inside every synthesizer and every tool on this site. Tone generator →

Phase / polarity: Phase is a waveform's position in its cycle; polarity is whether the signal is flipped upside down. Inverted polarity between stereo channels cancels bass and blurs imaging. Phase test →
Pink noise: Noise with equal energy per octave (−3 dB per octave tilt) - sounds balanced to human ears and is the standard signal for speaker calibration. Pink noise →
Pitch: The perceived highness or lowness of a sound - the perceptual counterpart of frequency, mostly determined by the fundamental.
Presbycusis: Age-related hearing loss, starting at the highest frequencies. The reason your ceiling frequency falls predictably with age. Hearing age test →

Resonance: A system's tendency to vibrate strongly at particular frequencies. Rooms, speaker cabinets, and instrument bodies all resonate - sometimes helpfully, sometimes not.
RMS: Root mean square - the effective average level of a signal, far closer to perceived loudness than peak level. Line-level voltages are specified as RMS.
Room mode: A standing wave between parallel room surfaces that boosts or cancels specific bass frequencies depending on where you sit. The dominant acoustic problem in small rooms. Room mode calculator →

Sample rate: How many times per second digital audio measures the waveform. 44.1 kHz (CD) captures everything up to ~22 kHz - the full range of human hearing.
Semitone: The smallest step in Western music - one twelfth of an octave, a frequency ratio of 2^(1/12) ≈ 1.059. Adjacent piano keys are a semitone apart. Transpose calculator →
Sine wave: The purest waveform: a single frequency with no harmonics. The building block all other sounds decompose into, and the standard test signal. Tone generator →
SPL (sound pressure level): Loudness in the air, in dB referenced to the threshold of hearing (20 µPa). Conversation ≈ 60 dB SPL; hearing damage risk begins around 85 dB for sustained exposure. Decibel meter →
Standing wave: A wave pattern that stays in place because reflections reinforce it - the physics behind room modes and the resonance of instrument strings and pipes.
Sweep: A tone that glides continuously through a frequency range - the fastest way to find dropouts, resonances, and rattles in a speaker or room. Sweep generator →

Timbre: The character that distinguishes two sounds of identical pitch and loudness - determined by harmonic content and how the sound evolves over time.
Tinnitus: Sound perceived without an external source, usually ringing or hissing, often linked to hearing damage. Broadband noise is a common masking aid. Tinnitus relief guide →
Transient: The brief, sharp onset of a sound - a drum hit's attack, a consonant. Transients carry rhythm and clarity and are the first casualty of over-compression.
True peak (dBTP): The estimated analog peak between digital samples after reconstruction. Streaming platforms ask for −1 dBTP ceilings so lossy encoding doesn't clip. Streaming loudness guide →

Waveform: The shape of a sound wave over one cycle - sine, square, sawtooth, triangle being the classic four, each with a distinct harmonic recipe and timbre. Waveforms guide →
Wavelength: The physical length of one wave cycle in air: speed of sound (343 m/s) divided by frequency. A 20 Hz wave is 17 m long; a 20 kHz wave is 17 mm.
White noise: Noise with equal power at every frequency - the audio analogue of white light. Sounds bright and hissy because most of its power sits in the top octaves. White noise →