Whether you’re just learning the ropes of audio or looking for something to guide you along the sales, buying, or education process, the following glossary breaks down some of the most commonly used audio terms in an easy-to-understand manner.
Acoustics: The sound wave behaviour in a given space.
Active Noise Cancellation (ANC): Instead of using a physical barrier to block the ambient noise, a headphone with ANC uses a microphone to register the ambient noise and attempts to reduce the extraneous noise electronically. Usually, an ANC headphone blocks the outside noise further by also using a physical barrier (such as a cup covering the entire ear) or a form-fitting acoustic foam in the case of earphones.
AES (Audio Engineering Society): This group draws membership from audio engineers, psychoacousticians, and audio professionals. Floyd O’Toole, the world-renowned psychoacoustician, and Paul Barton of PSB Speakers and NAD are longstanding members of AES. Members are given free access to the AES E-Library, which contains every paper ever published in the AES Journal or at an AES convention or conference; and exclusive online access to technical and creative tutorials, videos and articles.
Ambient noise: Sound that is extraneous to the intended and desired, also known as background noise. Examples might include HVAC, fan noise, or road noise.
Amplifier: An electronic device for increasing the strength of electrical signals to a level that is audible to human hearing. Bryston, for example, is the manufacturer of the measurably most accurate amplifier in the world. The Canadian company’s products are being used by professionals around the world, including at
the National Research Council in Ottawa.
Analog: A method of transmitting information by a continuous but varying signal. Vinyl and reel-to-reel are examples of analog sound sources. The presumption is that since everything we hear is in analog, an analog system will sound more “pure” than digital. In theory, digital is merely an analog approximation (note: this is false, but that’s a discussion for another article.)
Artifacts: Small disturbances that affect the quality of a given audio signal. Both analog and digital sources can have artifacts like garbled sound and distortion, amongst many others.
Audio processor: An electronic device used
to manipulate audio signals in some manner. For example: tone controls and equalizers manipulate the frequency response of a
given song by boosting or reducing certain frequencies. This audio processing can be done in both the analog or digital domain.
Balanced circuit: A circuit in which two branches are electrically alike and symmetrical with respect to a common reference point, usually ground; preferred to an unbalanced circuit due to its ability to reject noise.
Bass reflex (also known as a ported, vented box or reflex port): A type of loudspeaker that uses the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies.
Bi-directional/polar pattern: The shape of the region where some speakers produce the most pronounced sound, which is from the front and rear. The legendary Bose 901 speaker and some Definitive Technology speakers utilize this polar pattern, which is an attempt to create omni-directional sound. Most manufacturers have abandoned this method, however, since there is no substitute for real omni-directional sound.
Bit depth: The number of bits used to describe data. This correlates with the dynamic range of a given audio recording. CD, for example, has
a bit depth of 16-bit. Hi-Res audio files have bit depth that varies from 18 to 32. A recording with higher number bit depth, in theory, would have a higher maximum loudness and a softer minimum loudness, or in other words, wider dynamic range.
Bitstream: Although technically this can mean any stream of digital data, in the context of home theatre, bitstream is an audio output option on any media player that will output the audio data as-is, without any conversion. As logic dictates, the least amount of conversion done to a given signal, the better it will sound. In the case of Blu-ray’s object-audio, make sure that secondary audio on your Blu-ray player is turned to the “OFF” position.
Capacitance: The ability of a nonconductive material, such as the shielding of an audio cable, to develop an electrical charge, which can distort an electrical signal. In a speaker, wire, capacitance occurs between the cable’s two conductors; the resulting losses in electrical current, hence worsening the sound quality.
Capacitive reactance: The opposition
a capacitor offers to alternating current
flow. Capacitive reactance decreases with increasing frequency or, for a given frequency; the capacitive reactance decreases with increasing capacitance. The symbol for capacitive reactance is XC. It’s commonly
used in cable specifications.
Class (amplifier class): Represents the amount of the output signal that varies within the amplifier circuit over one cycle of operation when excited by an input signal. The most common classes are A, B, A/B, and D where class-A tends to give the most “warmth” in sound with the drawback of being highly inefficient (i.e. consumes a lot of power with an efficiency down to only 20% and emits a lot of heat) and class-D being highly efficient (about 80%, emitting virtually no heat) with the drawback of sounding “too clinical” and “sterile” for some listeners.
Closed headphones: A headphone architecture that isolates you from surrounding noise (thus also keeping others from hearing your music) consisting of a physical cup that encloses the back of the headphone drivers. Some headphone manufacturers market this closed architecture as “noise isolating technology.”
CODEC: An acronym for coder/decoder. An algorithm that converts analog signals into digital form (and back) and compresses them to conserve bandwidth on a transmission path. While there are hundreds of CODECs, the ones most commonly used are MP3, FLAC, ALAC, Dolby Digital, DTS and DSD.
Crossover: Circuitry inside a speaker enclosure that separates the audio frequencies going to each individual driver. There are two types of crossover: passive is usually installed inside a speaker enclosure, and active is an external electronic crossover with variable frequency cut-off points.
Crosstalk: Any phenomenon by which an audio signal from one channel leaks to another channel. The higher the crosstalk, the narrower the sound stage of a system. Crosstalk in the digital domain is non-existent. However, in analog, crosstalk will always be there to varying degrees due to the inherent design of analog media. The higher the crosstalk, the more what you’re listening to will sound like mono instead of stereo.
Current: The amount of electrical energy flowing in a circuit. A term used in amplifiers. The higher the current usually translates to better sound quality and faster transient in sound reproduction. Class-A amplifiers are known to have an extremely high current although, due to improvements in technology, any class of amplifiers can have a high current design.
dB SPL (decibel Sound Pressure Level):
A measure of sound pressure levels. For example, 85dB is an industry-accepted loudness for reference monitoring and listening for any given recorded material.
Decibel: A comparison of two measurements or values. Abbreviated dB, it is one-tenth
of a Bel (a unit of measurement named for Alexander Graham Bell).
Differential-mode: Refers to either noise or surge voltage disturbance suppression. The use of this suppression method yields a better sound quality. Usually used in DAC architecture. (See “Digital to Analog Converter or DAC”)
Diffusion: The scattering or random reflection of sound. When a sound hits an uneven surface, such as a shelf full of books or knick-knacks, the reflection will be randomly scattered.
Digital-to-analog converter (DAC): A device that converts digital signals into analog form. Since a human can only hear sound in analog form, a converter is needed when playing back any digital file.
DIN connector: Deutsche Industrie-Norm (DIN), a connector that follows the German standard for electronic connectors, found in audio equipment that conforms to European standards.
Direct sound: Also known as near-field, sound that is not coloured by room reflections.
This is achieved either by wearing a pair of headphones or listening to a recording through a pair of near-field monitors (speakers).
Dispersion: The angle of sound spread from a given speaker driver.
Driver: In audio, an individual speaker unit that produces a range of sound frequencies.
A tweeter, midrange, and woofer, for example, are speaker drivers.
Early reflection: Created by sound waves that are reflected (bounced) off surfaces between the source and the listener. The sound waves arrive at the listener’s ear closely on the heels of the direct sound wave.
EIA (Electronics Industries Alliance): The association that determines recommended audio and video standards in the U.S., to which AV manufacturers worldwide conform. Made up of various manufacturers and independent audio and video experts and consultants.
Electromagnetic interference (EMI): An electrical disturbance caused by an electromagnetic field, either low frequency or radio frequency (but not to be confused with Radio Frequency Interference). This can be caused by something as serious as an electrical storm, or as common as a cordless phone, Wi-Fi signal, or even microwave oven.
Equalizer: Electronic equipment that adjusts frequency characteristics of a signal. No longer popular in two-channel applications, although highly necessary in any audio calibration process in order to make a room’s frequency response as neutral as possible.
Fibre optic (Toslink/Optical connector): A technology that uses glass or plastic threads or wires to transmit information. The alternative to optical connector is coaxial connector, also known as “S/PDIF” or “Sony-Philips Digital Interface.” For home audio use, there is no advantage in using one over the other.
Frequency response: The range of frequencies a given component can reproduce. Frequency describes the number of waves that pass a fixed place in a given amount of time. Usually, frequency is measured in hertz, named in honour of the 19th-century German physicist Heinrich Rudolf Hertz. The hertz measurement, abbreviated Hz, is the number of waves that pass by per second. For example, an “A” note on a violin string vibrates at about 440Hz (440 vibrations per second).
Fundamental frequency: The lowest frequency in a harmonic series; known as “pure tone.”
Gauge: A thickness or diameter of a wire. The two most commonly used standards are American Wire Gauge (AWG) and Outer Diameter (OD). The thicker the wire, the higher the conductivity will be, which theoretically translates to better sound reproduction. The most common wire thickness used is 16 AWG and 12 AWG, although audiophiles sometimes go to great lengths to use even larger cable gauges, like 8 AWG. In the AWG standard, the lower the number, the thicker the cable.
Harmonics: Higher frequency sound waves that blend with the fundamental frequency.
Heat sink: A device that absorbs and dissipates heat produced by an electrical component. Amplifiers use the most heat sinks since they generate the most heat in contrast to other audio (and video) equipment.
Hertz (Hz): Cycles per second of an audio or electrical signal.
Hi-Res Audio: The Digital Entertainment Group, the Consumer Electronics Association and The Recording Academy teamed up with Sony, Universal and Warner Music Group to come up with a standard definition for high resolution audio: “Lossless audio that is capable of reproducing the full range of sound from recordings that have been mastered from better than CD-quality music sources.” This also includes Hi-Res audio recordings derived from analog sources.
Horns: A type of loudspeaker that uses a flared enclosure to focus its sound energy. The two most common brands that use this method are Klipsch and JBL.
Impedance: Opposition to alternating current measured in ohms; it may vary with frequency of the applied current. A speaker may have a nominal impedance of (say) 8 Ohms, but the actual impedance may vary from 2 Ohms to 16 Ohms, depending on the frequency it tries to reproduce.
Inductance: The ability of a magnetic field to transfer electrical current on a conductor; usually used when discussing a wire/cable.
Integrated amplifier: A combination of input selector, volume control (and sometimes
tone controls) and amplifier (see “amplifier”) integrated into a single unit. Some integrated amplifiers even include an AM/FM receiver and/or streaming capability.
Jacket: The outside covering used to protect wires in a cable and their shielding.
Jitter: A significant, and usually undesired, factor in the design of almost all communications
links, consisting of any type of error with data or timing. In audio, the lower the jitter, the better sound imaging/wider the sound stage. HDMI is inherently prone to jitter thus the need for a low- jitter clock to be used to lower the jitter value output via the HDMI output.
Lossless audio: A compression approach using an algorithm that does not cut out any data from the original file. FLAC, ALAC, Dolby TrueHD, DTS-HD-MA and DSD are some of the more popular lossless audio CODECs out there.
Loudspeaker driver: A transducer that converts electrical energy into sound.
Midrange: Loudspeaker driver that reproduces midrange frequencies, typically between 300Hz and 8,000Hz.
Monophonic: A single audio channel. Older recordings tend to be in Mono, such as the early recordings of The Beatles.
Moving coil: In a moving coil cartridge, the stylus cantilever carries a tiny coil, which is positioned between two sets of fixed permanent magnets (in a stereophonic cartridge), forming a tiny electromagnetic generator. As the coil vibrates in response to the stylus following the record groove, it induces a tiny current in the magnets. Moving Magnet cartridges tend to be used for more intermediate and higher- end turntables. Although this is considered a de-facto standard for higher-end turntables, this accepted notion is actually false. Just like any type of design, one can have a poorly designed moving coil system which, in return, performs worse than a moving magnet design.
Moving magnet: In a moving magnet cartridge, the stylus cantilever carries a tiny permanent magnet, which is positioned between two sets of fixed coils (in a stereophonic cartridge), forming a tiny electromagnetic generator. As the magnet vibrates in response to the stylus following the record groove, it induces a tiny current in the coils. Moving Magnet cartridges tend to be used for more entry level turntables. However, many Moving Magnet cartridges are as good or even better than their moving-coil counterparts.
Near-field: Also known as direct sound, it is the type of sound that has not been coloured by room reflections.
Object audio: Also called Immersive Audio or, less commonly, 3D Surround. The new surround format based on audio objects instead of channels that makes the soundtrack scaleable from as low as two-channels up to 32 channels around and above the listener for the most three-dimensional sonic experience. There are two variants in object audio, Dolby Atmos and DTS:X, that both essentially do the same thing, producing the same end result. Currently, there are more Dolby Atmos titles released worldwide compared to just a handful of DTS:X titles that have been released or announced.
Octave: A band, or group of frequencies. The relationship of the frequencies is such that the lowest frequency is half of the highest: 200Hz – 400Hz is an octave, 1kHz – 2kHz is an octave.
Omni-directional: The shape of the area for speakers that has equal sound dispersion to nearly all directions. An example is MBL speaker systems, which have drivers that “pump” sound in a spherical manner.
Open headphones: A headphone architecture where the backs of the headphones are open, resulting in more “airy” sound characteristics. The open headphone architecture is also useful when you need to be aware of your surroundings, such as while you’re riding a bicycle. On the other hand, this also means people around you will know what you’re listening to.
Optical connector: (See “fibre optic”)
Peak: The highest level of signal strength, deter- mined by the height of the signal’s waveform.
Phase: The relative timing of one signal to another.
Phone connector: An audio connector used as a headphone connector. Common types are 1/4 inch and 1/8 inch.
Phono connector: The European name for RCA connector.
Phono pre-amp: Record players send a quieter signal than other audio sources and therefore require additional amplification and re-equalization. All record players demand a preamp at some point in the signal chain.
If the preamp is not built into the receiving
end of the signal or into the record player itself, an outboard preamp will be necessary.
Pink noise: A sound that has equal energy (constant power) in each 1/3-octave band.
Point-source: A speaker system that has a central location for the loudspeaker(s) drivers, such as KEF’s UniQ and Pioneer’s CST drivers. This means the tweeter and the woofer are “sandwiched” together into one space.
Polar pattern: (See “bi-directional”) Ported: (See “bass reflex”)
Radio frequency (RF): Generally refers to signals such as radio, Wi-Fi, microwave and TV broadcast signals, or radio frequency control signals; the range of frequencies used for electrical transmission.
Radio frequency interference (RFI): Tendency of a radio transmission to interfere with other electronic signals. Radio frequency energy
is radiated by all electrical equipment, and when it is a strong enough signal, it becomes interference in audio systems.
RCA: A connector type most often used with line level audio signals; also known as a phono connector.
Reflection: Sound energy that has been redirected by a surface.
Reflex port: See “bass reflex”)
Reverberant sound: Sound waves that bounce off multiple surfaces before reaching the listener, but arrive at the listener’s ears quite a bit later than early reflected sound.
Sampling rate: How many samples of the analog signal are taken in a given time interval in creating the digital signal. The usual sampling rates are 44.1kHz (audio CD) 48kHz (Blu-ray movies) 96kHz, 192kHz (Hi-Res Audio).
Shielding: A physical layer in some cables used to protect signals and sometimes used as a return path for current. Three basic types of cable shielding are foil, braid, and combination.
Signal generator: Test equipment instrument that produces calibrated electronic signals intended for the testing or calibrating of audio systems.
Signal-to-noise ratio (S/N ratio): The ratio, measured in decibels, between the audio signal and the noise accompanying the signal. The higher the S/N ratio, the cleaner the quality of the sound.
S/PDIF (Sony-Philips Digital Interface):
A standard format for sending audio data from a sound source (such as a CD player) to a DAC. The most common connector used with an S/PDIF interface is the RCA connector; the same one used for consumer audio products.
Stereophonic: Commonly shortened to “stereo,” although technically, it means two channels or more, in the audio world, it strictly means two channels.
Streaming audio: Sequence of “sounds” sent in a continuous, compressed stream over the Internet and heard by the listeners as they arrive.
Stylus: The needle part of a turntable head assembly that reads the groove of a record.
Subwoofer: Also known as bass-module, a loudspeaker system that reproduces lower frequencies, and ranges between 20Hz and 200Hz.
3.5mm mini: A connector that is similar in appearance to a 1/4-inch headphone connector, but much smaller. It measures 3.5mm in diameter. In fact, all earphones and most headphones use this size connector. (Though some now come with a Lightning connector instead to accommodate the iPhone.)
Toslink: (See “fibre optic”)
Transmission line: A loudspeaker enclosure design that uses an acoustics waveguide inside its enclosure. A variation of a bass-reflex enclosure, but usually with more controlled and accurate bass reproduction. Thiel is one of very few speaker manufacturers that use this method.
Tweeters: Loudspeakers that produce high frequencies, typically between 2,000Hz and 20,000Hz.
Twisted pair: Any number of wires that are paired and twisted around each other; can be shielded or unshielded. Kimber Kable, for example, uses twisted pair construction for almost all of its products. The higher the number of twists per foot translates to a higher interference rejection, and thus the lower the amount of distortion carried by the wires.
Unity gain: Unity gain refers to no change in gain in audio signal. In many two-channel pre-amps or integrated amplifiers, it’s also called “Home Theatre Bypass.”
Vented box: (See “bass reflex”)
White noise: A sound that has the same energy level at all frequencies. The sound of torrential rain, or a waterfall, are common examples of white noise.
Woofers: Loudspeakers that reproduce low frequencies, typically between 20Hz and 200Hz.
XLR connector: Also known as “Balanced Connector,” a popular type of audio connector amongst audiophiles and professional applications featuring three wires: two for the signal and one for overall system grounding. A secure connector often found on high quality audio equipment.
Sources: Audio Engineering Society, Audioquest, AUVI, Kimber Kable, Tributaries, Wikipedia; notes from York University’s Electronic Music and Bridgewater University Psychoacoustics classes.