Common Audio Technical Terms That You Should Know – Glossary
All the technical jargon surrounding the headphone audio hobby can be tough to navigate. Don’t despair, we’ve got your back with this alphabetized list of useful technical terms.
Click the letters to jump to the relevant section:
A-Weighting Filter 🔗
A form of electrical filter designed to mimic the relative sensitivity of the human ear to different frequencies at LOW sound pressure levels, often used when making measurements of low-level sounds, like the noise floor of a device. The filter rolls-off the low frequencies below 700Hz and highs above 10kHz.
A circuit capable of amplification, containing transistors, integrated circuits (ICs), tubes and other devices that require power to operate.
The transmission of sound waves within environments with respect to their design.
Unwanted harmonic frequencies added to the audible signal when converting analog to digital, due to insufficient sampling rate (less than twice the highest frequency component of the input signal).
A device that increases the power level from a low level to a high enough level to drive a diaphragm (speakers or headphones) to produce sound.
The waveform signal level of acoustic sound (pressure) or electrical signal (voltage).
A circuit that uses continually changing voltage or current that tracks the original acoustic or electrical signal. Refers to the signal in the device being ‘analogous’ to the original signal.
Anti-alias Filter 🔗
A steep low-pass filter used to limit the frequency range (where the maximum frequency does not exceed ½ of the sampling rate) of an analog signal prior to digital conversion.
Reduction of the amplitude or level of a signal.
Audio Chain 🔗
A series of interconnected audio equipment, from source to transducer.
Audio Frequency 🔗
The audible frequency range (20Hz to 20kHz).
Someone who is enthusiastic about high-fidelity sound reproduction. They revere both the music and the equipment that plays it. Not the instruments used to create music, but the playback devices, speakers, amplifiers, DACs, headphones, etc. It’s said that a true audiophile listens as much (or more) to the equipment than they do the music.
Background Noise 🔗
Unwanted sound from all sources unrelated to the desired sound.
A circuit consisting of two equal but opposite polarity signals on two conductors used to reduce susceptibility to unwanted noise. Balanced headphones and amplifiers have four conductors (and related connectors) where the normal and inverted audio signal drives the + and – side of the driver coils. This eliminates cross-talk, doubles the slew rate, increases output power, doubles the output impedance, and halves the damping factor.
Band-Pass Filter (BPF) 🔗
A filter that attenuates signals above and below a setpoint.
The range of frequencies within a signal.
Behind-the-Neck Headphones 🔗
Headphones with a ‘neckband’ that fits behind the neck rather than over the head, often used in exercise due to stability during movement.
A method of recording audio which uses a special microphone arrangement to mimic two ears, that, along with frequency cues, allows the listener to determine the direction and origin of sounds.
A contraction of ‘Binary digit’ (either 0 or 1).
Eight bits of digital data.
Bit Rate 🔗
The number of data bits replayed or transferred in a given period of time (normally expressed in Kbps (thousand bits per second).
Unwanted leakage of sound.
To increase a signal. The opposite of attenuate.
C-Weighting Filter 🔗
A form of electrical filter designed to mimic the relative sensitivity of the human ear to different frequencies at HIGH sound pressure levels, often used when making measurements of high-level sounds, like calibrating loudspeaker reference levels. The filter rolls-off the low frequencies below 20Hz and highs above 10kHz.
A passive, two-terminal electrical component that stores energy in the form of an electrostatic field and releases it when needed by the circuit.
A path for carrying audio or data, typically expressed as left or right for 2-channel audio.
Slang for ‘Integrated Circuit’ or IC.
“Around” or “over the ear” headphones with large ear pads that completely surround the ear. More comfortable but at the expense of size and portability.
Clamping Force 🔗
A measure of how strongly the headphone presses into the sides of the head. Ideally a balance between comfort and stability.
Distortion occurs when an amplifier is driven into overload, causing the sound to become hard and edgy.
When the sample rate of one digital device is controlled by an external clock signal received from another device.
Closed headphones have a sealed cup that fully encloses the rear of the driver, which creates passive external noise reduction (isolation), and tends to increase bass response.
The 75 Ohm S/PDIF digital audio input and cable with an outside conductor which completely surrounds a center conductor. Both conductors share the same center axis and are therefore considered “co-axial.”
An encode / decode process (coder-decoder) where a signal is encoded into a specific format before transmission or recording, and then decoded on reception or replay, either analog codec (Dolby A or Dolby B tape noise-reduction systems) or digital (FLAC).
An interference effect in which the frequency response exhibits regular deep notches created when a signal is combined with a delayed version of itself.
Common Mode Rejection 🔗
A measure of how well a balanced circuit rejects an interference signal that is common to both sides of the balanced connection.
Limiting the reproduction of sound by reducing a magnitude of amplitudes.
A material that provides a low resistance path for electrical current.
A device that transforms audio signals from analog to digital (A-D) or the reverse (D-A).
An electronic circuit that delays the signal from each channel and feeds it to the other channel, to mimic the acoustics of listening to a 2-channel speaker system (how sounds from both speakers reach the ears), designed to improve the audio image and reduce listening fatigue.
Typically a set of hardware filters designed to restrict signal frequencies sent to each driver so that each only receives the frequencies it can best reproduce.
Crossover frequency 🔗
The frequency where one driver rolls-off and another driver takes over sound reproduction.
One complete vibration of a sound source or its electrical equivalent (from the maximum positive peak, through the negative peak, and back to the maximum again) expressed as cycles per second, Hertz (Hz).
A Digital to Analog Converter is a device that converts digital files to analog signals for playback.
Daisy Chain 🔗
Connecting the output of a device to another which feeds yet another device in a series.
The control of resonance by absorbing reverberant energy.
Damping Factor 🔗
The ability of the amplifier to control driver motion once the signal has stopped. Measured as the ratio between the driver impedance and amplifier impedance, and is expressed in the format ‘2:1’. Most apparent in low-frequency reproduction, where low damping can cause loose, boomy, and indistinct bass, while high damping tends to make bass sound tighter and cleaner, but subjectively less warm.
Decibel (dB) 🔗
A method of expressing the ratio of audio signal amplitudes (or relative output sensitivity) in a logarithmic fashion. If one signal has twice the amplitude of the other, the decibel value is +6dB, and if half the size, -6dB. When discussing acoustic sound levels, 0dB SPL (sound pressure level) is the typical threshold of human hearing at 1kHz.
A method of measuring the slope or steepness of a filter, from 6dB/Octave (first-order slope) to 24dB/octave (fourth-order), which is the steepest normally found in analog audio applications.
Direct Current indicates a single direction current flow, such as supplied by batteries and the power supplies inside electrical equipment.
DC Coupling 🔗
Also referred to as AC-Blocking, allows both AC (audio) and DC (control voltages) to pass into or out of an amplifier or other circuit.
Latency or the time between a sound being generated and it taking effect.
The movable membrane in a speaker, headphone, or microphone contained in the driver that produces (or receives) audible sound waves.
A method of representing a continuously variable audio signal as binary values (0s and 1s). The audio bandwidth is restricted by the sample rate, and the signal-noise ratio (or dynamic range) is restricted by the word-length.
Digital Inputs 🔗
Any input to a digital to analog converter (DAC) including USB, or S/PDIF Toslink optical or coaxial.
Direct Coupling 🔗
A means of connecting two electrical circuits so that both AC and DC signals may be passed between them.
Audible or inaudible changes to the musical signal.
Either software that handles communications between a digital device and hardware peripheral, or the physical element inside a headphone, or speaker, that converts an electrical signal into audible sound waves. Headphones may use dynamic, balanced armature, planar magnetic, or electrostatic driver types.
Dynamic Range 🔗
The difference in decibels between the loudest signal and the quietest audible sound.
Small earpieces that are designed to rest in the outer entrance to the ear canal. They differ from IEMs (In-Ear Monitors) that protrude into and seal the ear canal.
Ear Cup 🔗
The portion of headphones that contains the driver.
Ear Pad 🔗
The ring-shaped cushion (typically made of foam, velour, synthetic, or actual leather) that sits between the ear cup and the head, primarily designed to improve wearing comfort, although has a large influence on sound reproduction.
The relationship between input signal level and volume. Also referred to as Headphone Sensitivity, it is a measure of how much energy it takes to drive headphones to a given listening level.
The shape of the graph as amplitude is plotted against time and includes attack, decay, sustain, and release (ADSR) phases.
A device or software which allows the user to adjust the tonality of a sound source by boosting or attenuating a specific range of frequencies.
An electronic circuit designed to attenuate a specific range of frequencies.
Filter Frequency 🔗
The frequency at which the signal amplitude has been attenuated by 3dB of a high- or low-pass filter.
Fletcher-Munson Curve 🔗
Human sensitivity to sound, depending on frequency and volume. At lower volume levels, bass and treble sounds seem reduced in intensity, as they are farther from midrange sounds.
The number of complete cycles (vibrations) of a repetitive waveform that occur in 1 second, measured in Hz (Hertz). Pitch increases with frequency.
Frequency Response 🔗
Measurement of amplitude relative to the signal frequency, which establishes the range that can be handled by a specific piece of audio equipment. “Flat” frequency response is when the gain is constant at all frequencies.
Fundamental Frequency 🔗
The lowest frequency component in a harmonically complex sound.
The amount, or ratio by which a circuit amplifies a signal, measured between the output and input levels, in decibels (dB).
Gain Switch 🔗
Fixed-point volume control for adjusting an amplifier for headphones of differing impedance and sensitivity.
Graphic Equalizer/EQ 🔗
A type of equalizer where individual cut/boost faders control narrow segments of the audio spectrum. The fader positions provide a graphic representation of the EQ curve.
Ground Loop / Ground Loop Hum 🔗
Unwanted audible noise created between interconnected devices.
Harman Curve 🔗
A specific target for headphone frequency response created from the 2012 paper, titled “The Relationship Between Perception and Measurement of Headphone Sound Quality,” that strives to reproduce the sound of listening to stereo speakers, by increasing bass and treble response.
The number of frequencies within a sound, where the harmonic frequency is an integer multiple of the fundamental which establishes the timbre or tone of the note.
Harmonic Distortion 🔗
The addition of artifacts that were not present in the original signal that are exact integer distances higher in frequency than the originating tone.
Headphone Amplifier 🔗
An audio power amplifier specifically designed to drive headphones, differing primarily from stereo amplifiers, by requiring much lower power, lower output impedance, and by being capable of driving a wider range of impedances (typically between 10-600 Ohms).
The ability of an amplifier to go beyond its rated power for short durations in order to reproduce musical peaks without distortion, defined as the region between the nominal operating level and the clipping point.
Hertz (Hz) 🔗
The standard measurement of frequency expressed in cycles per second.
High Resolution 🔗
Typically refers to digital formats with high bit and sample rates greater than the CD standard of 44.1 KHz/16 bit.
High-Pass Filter (HPF) 🔗
A filter that attenuates frequencies below its cut-off frequency.
Unwanted audible noise caused by random electrical fluctuations.
Discomfort on a portion of the head caused by a headphone’s band not properly supporting or distributing the weight.
Unwanted audible low-frequency noise, usually related to the mains power frequency.
The sum of both resistive and reactive resistance to AC current measured in Ohms. When viewed as a simple electronic circuit, the impedance of the audio source may be written as output (or source) impedance, while the impedance of the headphones may be considered load impedance. Headphone impedance commonly changes with the signal frequency.
In-Ear Monitor (IEM) 🔗
Originally intended for live musicians, now a popular type of headphone that inserts into the ear canal. Also known as ‘Intra-aural’.
A material that does not conduct electricity.
The interaction between combining multiple sound waves or electrical signals.
Frequencies introduced into the signal based on the sum and difference products of the original frequencies.
Measurement of external or ambient sound blockage.
A 2.5, 3.5mm or 6.35mm (1/4”) diameter audio connector.
K-Weighting Filter 🔗
A form of electrical filter designed to mimic the relative sensitivity of the human ear to different frequencies in terms of perceived loudness (similar to A-Weighting plus a boost above 2kHz).
The strength of an audio signal used to transmit analog sound between audio components.
The ratio of an acoustic quantity (amplitude) to a reference quantity.
The output of a device is a direct multiple of the input, usually in solid-state, class A/B push/pull amplifiers.
The sensation of the magnitude or volume of sound level.
Loudness Wars 🔗
The trend over time of increasing the audio levels in recorded music, making it subjectively louder, but reducing audio fidelity.
Lowpass Filter 🔗
A filter that attenuates frequencies above a specified frequency.
The amount by which one sound is affected by the presence of another sound. The masked threshold is the quietest level where the signal may be perceived when combined with a specific masking noise.
A single channel of audio.
To greatly attenuate the volume level.
Electrical interference or other unwanted sounds introduced into the audio system.
Noise Canceling 🔗
A circuit that utilizes a microphone to reject ambient sounds and to provide acoustic isolation, by producing a signal which is fed into the headphone which counter-balances and cancels the unwanted noise.
Nyquist Theorem 🔗
A rule which states that a digital sampling system must have a sample rate at least twice as high as that of the highest audio frequency being sampled.
The doubling or halving of frequency or pitch.
The unit of electrical resistance.
On-Ear Headphones 🔗
A type of headphone where the earpad is sized to rest upon the ear. Also known as supra-aural.
Operational Amplifier (Op-Amp) 🔗
An electronic amplification circuit with an inverting and non-inverting input and an output.
Open-Backed Headphones 🔗
When the earcups are not enclosed or are vented, which typically leaks sound, and allows more ambient sounds to intrude, but can have a more natural soundstage.
Output Impedance 🔗
The effective internal impedance of an audio device such as an amplifier or source.
Output Transformer-Less (OTL) Tube Amplifiers 🔗
OTL amps use capacitive coupling, or DC coupling, instead of transformers to increase the current and decrease the signal voltage for playback.
Over-Ear Headphones 🔗
“Around” or “Circumaural” headphones with large earpads that completely surround the ear. More comfortable but at the expense of size and portability.
Any frequency that is greater than the fundamental frequency of a sound.
A circuit with no active elements.
The maximum instantaneous level or amplitude of a signal.
The position of a point in time on a waveform cycle.
Phase Cancellation 🔗
Undesirable dips and peaks in frequency response caused by mixing the same signal but with different arrival times.
The hollow sound as a result of two identical waves combining.
Phono Plug (RCA Plug) 🔗
The ubiquitous audio connector developed by RCA for unbalanced analog signals, and S/PDIF digital signals.
Pink Noise 🔗
A random, natural-sounding, signal with a power spectral density which is inversely proportional to the frequency.
The musical interpretation, or fundamental, or basic of an audio frequency or musical note.
A signal’s voltage above or below the median.
Power Supply 🔗
The circuitry that converts the AC wall voltage into usable DC supply voltages inside a device.
Measurement of quality or resonant properties of a filter. Higher Q values indicate higher resonance and a resulting narrower range of frequencies that it allows to pass.
The distance between the lowest and highest tones.
Red Book CD 🔗
The original specifications documents for the standard audio CD created by Sony and Philips had a red cover.
Opposition to the flow of current in an electrical circuit. Measured in Ohms.
The characteristic of a filter that allows it to selectively pass a narrow range of frequencies. Also the characteristic of physical devices to vibrate or ring (such as a bell).
The gradual decrease of a signal once it has passed a specific frequency.
Sample Rate 🔗
The number of times per second that an Analog to Digital converter samples the incoming analog wave.
Semi-Open or Semi-Closed Headphone 🔗
The headphone’s ear cups are not fully open nor fully closed.
Also known as efficiency, it is a measurement of headphone volume at a specific power rating.
Signal Chain 🔗
The path of components and interconnects taken by a signal from the output of the source to playback.
Signal-To-Noise Ratio (SNR) 🔗
The distance between the lowest audible level (noise floor) and the music signal.
Solid State 🔗
An electronic circuit that uses semiconductor devices such as transistors, diodes, and integrated circuits to provide gain, as opposed to tube-based designs.
Sound Pressure Level (SPL) 🔗
A measure of the intensity or strength of a sound, rated in decibels.
Stereo/ Stereophonic 🔗
Left and right, 2-channel audio, which creates the impression of 3-dimensional and distinct sound source positions.
Switching Power Supply (SMPS) 🔗
A type of power supply that drives a high-frequency oscillator and smaller transformer to convert mains power to a usable level.
Total Harmonic Distortion (THD) 🔗
A measurement of the harmonic distortion (the ratio of harmonics to fundamental) present in a signal, often serving as a measurement of device linearity and quality of an audio device.
An electronic device that converts one form of energy into another. A microphone transducer converts acoustical energy (sound) into electrical energy (the audio signal), while a speaker or headphone transducer does the opposite.
An electrical device based on electrically isolated wires coiled around a shared ferromagnetic core used to convert (both increase and decrease depending on the ratio of the number of coils) AC voltage.
An electronic component that can provide electrical signal gain.
Tube/Vacuum Tube/Electron Tube/Valve 🔗
A glass tube containing electrodes in a vacuum, for controlling electron flow, used as an audio amplifier (as well as other purposes).
A typical unbalanced (single-ended) headphone amplifier derives its name from the relative impedance to ground of the two connections in each channel (hot or positive and ground or negative). Because the impedance to ground differs, we call it unbalanced.
Unity Gain 🔗
The output signal is the same amplitude as the input signal.
Universal Serial Bus (USB) 🔗
A standardized computer interface introduced in 1996 that can also provide a 5V power supply to connected devices in addition to data transfer.
The latest (2014) incarnation of the USB interface, capable of carrying bidirectional data at speeds of 10Gb/s, with a symmetrical 24-pin connector and a 5V current capacity of either 1.5A (7.5W) or 3A (15W).
The potential difference in an electric circuit.
Common terminology referring to the perceived level of sound.
VU Meter 🔗
An audio meter designed to interpret signal levels which generally corresponds to perceived loudness.
Watt (W) 🔗
A unit of electrical power, that quantifies the rate of energy transfer, named after its founder, James Watt.
A regular variation in electrical signal level or sound pressure level.
A graphic representation of how the shape of a sound or electrical wave varies over time.
The physical distance between the start and end of one cycle of a sound wave.
White Noise 🔗
A bright sounding, random signal with equal power within any frequency band of a fixed width.
The electromagnetic transfer of information between two or more devices that are not connected by an electrical conductor, typically done with a Bluetooth connection for wireless headphones.
Word Clock 🔗
A device that identifies the start and end of each digital word or sample for interconnected digital audio equipment.