Aanvil
A tiny bone inside your ear that is so named due to its slight visual similarity to an anvil, it is connected to a tissue that acts as a transducer converting the vibrational information into neural signals, which are then fed into your brain. The anvil is normally excited by the eardrum, in other words this bone is what allows you to hear sounds.

However the aanvil is the evolutionary remains of a larger bone that formed a part of the jaw, for that reason there is still a connection between your cheekbones and the aanvil which is the reason you can hear yourself eating etc., the "bone phone" and similar loudspeaker less headphone units commonly referred to as "bone conducting headphones" take advantage of this anomaly to excite the aanvil by placing a transducer on your cheekbones rather than your ears, while those devices never sound as good as normal headphones they do have a couple of advantages, namely that it is impossible to harm the eardrum by using them and you can still hear with your ears while they are used.

Accumulator
Arcane name for a rechargeable battery.

Acoustics
1) The science of sound. 2) The effects that an environment has on a sound.

Active See --> amplifier

A/DC = Analogue to Digital Converter
A device that converts analogue electric signal or signals into a digital signal.

Alesis syndrome
What happens when a piece of equipment placed into a rack lowers the sound quality or causes noise problems with other equipment in the rack, this was often explained away as a psychological thing (e.g. place a cheap Phonic in the rack and the whole unit looks cheaper) but is actually a bona fide technical issue. In the 1980’s recording studio engineers noted that inexplicably enough inserting an Alesis Corp. effect processor into the rack appeared to lower the sound quality of the other equipment in the rack with some high end analogue processors and Lexicon reverbs in particular having problems.

This is simply a grounding issue, to save money the Alesis boxes used cheap AC/AC wall warts rather than built in power supplies with regulator being built into the processors themselves, this leaves the AC/AC converter grounded but not the effect unit itself. In most other cases such equipment uses AC/DC wall warts which leaves the unit decoupled from the mains or in the case of consumer equipment devices with AC/AC supplies or non-rack equipment like drum machines, the equipment casing does not touch other grounded surfaces and thus does not earthen itself, the 19” racks used in pro-audio however leaves all the units inserted into the rack electrically connected to each other via the rack rail and because the metal cases often touch one another anyway, this is not a problem with normal studio equipment since they are all grounded via the power plug but the Alesis devices grounded themselves via the other equipment in the rack causing interference with sensitive circuits such as Class A gain stages resulting in increased audio and electrical noise and in rare cases hum issues.

This problem can be fixed by either grounding the offending device separately, if you have it hooked up to a mixer that also has phono inputs you can use the grounding terminal on an unused phono input. Alternatively you can electrically isolate the unit from the rest of the rack by masking the back of the ears with electricians tape and using plastic spacers between the bolts and the unit, and if needed, plastic sheets on the top and bottom of the unit itself.

AlNiCo = Aluminium, Nickel & Cobalt Magnets
An Hard Magnet alloy with a unusually dense magnetic field especially if cast rather than sintered, is extremely temperature stable for a magnet, mechanically strong and extremely corrosion resistant, or in other words, an ideal magnet for any sort of transducer manufacture. Originally invented in 1931 and in addition to the metals that make up the name there is invariably a tiny bit of copper in there as well, given an almost mythical status by some audiophiles but expensive compared to Neodymium and other similar magnets, slightly more difficult to work with than the more common magnetic materials and easily demagnetised so mostly used in high end products. Never use a standard cartridge demagnetiser on a pickup made using an Alnico magnet! Something like the Gryphon demagnetiser should be OK though.

AM = Amplitude Modulation
A technique where information content is added to a wave by modulating the amplitude of the wave.

In radio : To get audio data onto a radio wave the amplitude (signal strength) of the wave is modulated while the frequency remains constant, this is the opposite to an FM radio where the frequency is modulated while the amplitude axis remains constant. Originally invented for use in telephone equipment, this technique was then introduced to radio in the 1910's. Still used in low bandwidth radio transmissions (Long Wave, Short Wave and Medium wave bands) but never used at ranges that allow for more bandwidth since more modern techniques can pack more information onto such signals.

Amplifier
A circuit or a device that increases the power of a signal.

Pre-amplifier : A small signal amplifier that brings a signal or signals up to a common standard which is then further amplified, by far the most common version of this is the control amplifier (below) but in modern usage the 2 are usually synonymous, but lots of specialised pre-amplification devices exist, a Head Amplifier and RIAA preamplifiers are a good examples of this.

Control amplifier : A device that acts as the control unit for an audio system, compromising of a number of pre-amplification circuits that interface units with specific output characteristics to a common standard and also allows the users to control which signal is sent to the amplifier and at what strength (i.e. volume). A control amplifier often also allows the user to perform householding tasks such as equalisation or other filtering, re-routing signals to a recording device and so on. In modern times all incoming and outgoing signals are line level which has given birth to a variant of the control amplifier called a line stage in which the device only features an input selector switch and a preamplifier section with volume control.

Power amplifier : An amplifier that increases a signals strength to a degree that it can be used to drive a loudspeaker with, a power amplifier intended for home usage almost invariably has a set amount of amplification so the loudness is controlled by the incoming signal which is typically a control amplifier or a similar preamp such as a mixer, power amplifiers intended for professional applications however often have a variable gain for each channel.

Integrated amplifier : 1) A device that combines the functions of a control and power amplifier into a single unit. 2) A power amplifier built into a device that typically does not feature it such as a mixer or a loudspeaker, that case the device is often referred to as "Active".

Passive pre/control amplifier/line stage Not an amplifier at all but a passive functional replacement for a control amplifier, basically you get a number of switches that allow you to choose between inputs and an attenuator, usually a variable resistor, a bank of switched resistors or a transformer, that allows you to control the strength of the signal that is delivered to the power amplifier and thus the volume coming out of the speakers. This sort of a design takes advantage of the fact that almost all modern audio and AV devices feature line level outputs and thus do not need amplification or equalisation prior to being sent to a power amp. There also exist minimal devises that have just an attenuator and no switching capabilities, these are useful only for systems with only one source component.

Analogue
A electical or mechanical representation of a sound where the representation is analogus to the original signal, e. g. a recording of a sinus wave will result in electronic signal or mechanical record that resembles a sinus wave. This is the opposite to encoded systems of any sort where the representation of a signal does not resemble the original one unless it has been through a conversion process, by far the most common of those is digital encoding of some sort

Analogue Synthesiser : A type of electronic musical instrument that creates sounds out of component structures and has the signal path totally analogue, the instrument can be constructed out of analogue or digital electronics, although it is usually a hybrid of both technologies, the opposite term is digital synthesiser. Slang usage : Amongst musicians the term analogue synthesiser has become synonymous with the term subtractive synthesiser, that is regardless of if the device or software is analogue or not.

Analogue Subtractive Synthesiser : A subtractive synthesiser implemented using analogue or digital technology that has a signal path that is purely analogue.

Archaeoacoustics
Basically the idea that you can retrieve sounds or other vibrational information from materials that predate the invention of audio recording, a pipe dream with a somewhat limited foundation in science (i.e. it's possible but the retrieved information is so small as to be useless), but still holds a fascination for a number of people.

Architectural
An American idiom which is used for audio and video products that are built into "the architecture", i.e. in the walls, floors or ceilings of a house in order to make them invisible or at the least less obtrusive, but in some quarters the usage of the term has expanded to mean any brown goods that are hidden from view.

ATC/Automatic Tape Calibration See --> ATC

ATRAC = Adaptive TRansform Acoustic Coding
Sony's property perpetual coding & compression system that is used on their Mini Disc and some of their solid state based music players. Works on similar princips to MPEG compression as used in MP3's (see PASC), basically an audio signal is split into 52 bands exponentially (i.e. the higher the frequency the wider the bands), all data that is duplicated inside each band is then removed, all data that the processor thinks the user will not hear due to the masking effect of the ears and all data it thinks is superficial (i.e. silence) is also removed and so on until the data has reached a reduction of 4,83:1 (or 292 kbs for a 16b 44KHz signal).

Initial versions of the ATRAC codec were absolutely horrendous, the quality of recordings made by early MiniDisc recorders were much worse than could be archived with a reasonable hi-fi cassette recorder, but improvements in the technology meant that by 1997 (ATRAC v4) or so the technology was becoming much more useful and today's models are quite good. Like all perpetual coding schemes ATRAC has problems with harmonically rich music, quick variations in dynamics and harmonics and the masking/compression artefacts can be irritating to some listeners (since the masking effect varies from person to person). It's not only the version of the codec (currently v6) that matters but also the power of the DSP that performs the work, the more expensive models of MD recorders often have more powerful processing chips and/or use more than one chip for the encoding process.

Even though later versions of ATRAC were quite good all things considered, its proprietary status meant that the standard became irrelevant and by 2010 even Sony music players no longer supported it..

AT&T/ATT See --> S/PDIF

Audible Range
The portion of the sound spectrum that humans can sense directly via their ears, commonly taken to be 20Hz to 20kHz. This is theoretical as much as practical since what you can hear and how you process that information varies not only from person to person, but may vary from day to day specially in regards to the higher frequency ranges and changes quite dramatically with age as well. Few grownups can hear anything directly over 14kHz or reliably under 70Hz while teenagers frequently can hear up to 23 kHz, even if not in a linear fashion.

Note that sound waves that fall outside the audible range can affect sound propagation inside it, directly and indirectly, and you can sense portions of the sound spectrum with other organs of your body although the brain does not process that information in the same way.

Autoblend See --> High Blend

Automatic Tape Calibration See --> ATC

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