Surround Sound
A surround sound format comprising 5 full bandwidth channel (left, centre, right, left surround and right surround) plus a low frequency effects channel.

ADPCM
Adaptive Differential Pulse Code Modulation; an audio compression scheme which compresses from 16-bit to 4-bit for a 4:1 compression ratio.

AIFF
Audio Interchange File Format; originally developed by Apple for storage of sound in the data fork of Macintosh files.

Amp modeling
The reconstruction of different guitar and bass amplifier models by software alone. When its well programmed the program reacts exactly like the real thing when you turn the knobs on the screen. Often you can also choose from a variety of cabinets or speakers to make the sound even more realistic.
AVI
Audio Video Interleave; Also called Video for windows. It is a special case of the RIFF (Resource Interchange File Format), defined by Microsoft and is the most common format for audio/video data on the PC.

Beat
The basic rhythmic unit in a piece of music. When you have a straight 4/4 rhythm a beat means 1/4 note.

Bit-depth
Just as the sample rate determines the frequency resolution, the bit depth determines the amplitude resolution. A bit is a computer term meaning a single number that can have a value of either zero or one. A single bit can represent two states, such as on and off. Two bits together can represent four different states: zero/zero, one/zero, zero/one, or one/one. Each additional bit doubles the number of states that can be represented, so a third bit can represent eight states, a fourth 16, and so on. Higher bit depths provide greater dynamic range.

CD-M (CD+MIDI)
Compact Disc-Musical Instrument Digital Interface; A CD-system on a computer that enables the user to work with MIDI instructions for electronic instruments, including reading musical scores and editing. CD-MIDI can display visual information that corresponds with the sounds as they are played.

Chorus
time to create a shimmering effect. makes a single voice sound like multiple voices in unison. You can implement chorusing by sending a sound through a series of delays whose delay times are slowly being modulated.
CODEC
Coder/decoder. When talking about data transmission, a coder/decoder is a device or algorithm which works on a bidirectional data link, coding transmitted and decoding received data. Audio codecs usually use computer files, multimedia data streams or TV broadcast channels for their data.

Compression
(1) Decreasing the size of stored information by reducing the representation of the information without significantly diminishing the information itself, usually by removing redundancies. Requires decompression upon retrieval. Lossless compression allows the original data to be recreated exactly. Lossy compression sacrifices some accuracy to achieve greater compression.

Reverb
In acoustics, an echo is the convolution of the original sound with a function representing the various objects that are reflecting it.

Crossfade
A technique commonly used in editing audio. One sound is faded out while another fades in, allowing for a smooth transition between the two. Crossfading is also common in samplers, where it is used to smooth loop transitions (crossfade looping), and sound design to create hybrid sounds (one sound morphing or turning into another). While we often think of this as a digital process, audio engineers have been using two channel faders on a mixing console to crossfade between two signals or tracks for many years.

Dial tone
The tone heard in a phone when the receiver is picked up, indicating the line is available for dialing.

DirectX
DirectX is an API (application programming interface) for demanding multimedia applications. It provides fairly direct access to the hardware and handles tasks like full-color graphics, games, video, and 3-D animation. DirectX provides a standard development platform for Windows-based PCs by enabling software developers to access specialized hardware features.

DMA
Direct Memory Access/Addressing. DMA is a method of transferring data from one memory area to another without having to go through the central processing unit. Computers with DMA channels can transfer data to and from devices much more quickly than those in which the data path goes through the computer's main processor.

DTMF
Dual Tone Multi-Frequency signals are used by standard push-button telephones. They are generated using combinations of 679-, 770-, 852-, 941-, 1209-, 1336-, 1477-, and 1633-Hz sine waves.

Flanger
An audio effect caused by mixing a varying, short delay in roughly equal proportion to the original signal. The name comes from how the effect was produced on big tape reels whereby the flange of the reel was tapped to slow down a copy of the signal hence produced phasing effects in the output.

FM synthesis
Frequency Modulation Synthesis; a music simulation technique that approximates the sounds of real instruments by modulating and bending raw electronic wave forms. The first real popular instrument that used this sound generating technique was the famous Yamaha DX7 keyboard.

Frequency sweeps
An oscillator starts generating a waveform at a certain (usually low) frequency and changes the frequency at a defined speed to another frequency (usually high), without changing the amplitude of the waveform. This is useful to determine the frequency response of circuits, rooms, speakers etc...

Harmonic (overtone)
Given a signal, we can decompose it with the Fourier transform. Then, a harmonic (of some particular frequency present in the transform) is any frequency (also present in the analysis) which is at a whole number ratio to our base tone. If the signal is periodic, every partial present in the analysis is harmonic.

High definition audio
Intel® High Definition Audio (HD Audio) is the specification for the next generation integrated audio solution. First announced at the Intel Developer Forum, Spring 2003, and gaining rapid adoption by the PC audio community, it is intended to be a complete audio specification from the jacks in the PC to the driver layer of the OS.

Latency
In general the time lag between a request and the action being performed. Latency can reflect network time delays or MIDI and audio playback timing errors. Regarding audio interfaces like soundcards it's the delays occurring when you're recording or playing back. This delay is known as soundcard latency. It depends on the processing power of the soundcard, the drivers and the speed of the host computer.

Marker
A Symbol like a colored vertical line that identifies a specific position in a sound or video file. You can save it with the sound file. They can be used to mark looping points, for designating regions in a file or just to remember points of interest like glitches, song start and end or rough descriptions of the content. You normally can label a marker and search for it later.

Metadata Commands
Metadata command markers indicate when an instruction (function) will occur in a streaming media file. You can use command markers to display headlines, captions, link to Web sites, or any other function you define.
MIDI
Musical Instrument Digital Interface. A standard protocol for communication between electronic musical instruments and computers. It transmits information of which notes should be played how loud and other control information like volume, pan etc. Normally it doesn't transmit any audio data except sending short sound samples via Midi SDS.

Modulation
The variation of some characteristic of a signal or a parameter of an algorithm producing the signal to achieve some specific goal.
MP3
MPEG1 or 2, layer 3 audio coding; a lossy, perceptual audio coding format widely used for the transmission of stereophonic sound, both in commercial and non-commercial environments. Layer 3 is the most sophisticated of the 3 layers specified for MPEG1 and MPEG2 (They share the same audio bitstream formats, only the allowed bitrates differ.

MPEG
Motion Picture Experts Group; a joint consortium of motion picture engineers. Standardizes movie related material. Commonly known for its MPEG1, MPEG2 and MPEG4 standards, which pertain to the digital coding and transmission of moving picture and associated sound (MPEG1-2), and multimedia (MPEG4).

Noise reduction
There are basically two types of noise reductions in use. Single and double ended systems. Single-ended noise reduction systems use dynamic filters to reduce the level of audible noise in a signal.

Normalize
To boost the level of a waveform to its maximum amount without clipping, limiting, compressing or changing it in any other way. This maximizes resolution and minimizes certain types of noise like aliasing.

Notch filter
A filter that eliminates a narrow frequency range from a signal without affecting the rest of the sound.

Ogg Vorbis
Ogg Vorbis is an open source audio codec designed to compete with MP3. Since it is not licensed like MP3, software using this codec does not have to pay royalties.

PCM
Pulse-code modulation (PCM) is a modulation technique. It is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals. Every sample is quantized to a series of symbols in a digital code, which is usually a binary code. PCM is used in digital telephone systems. It is also the standard form for digital audio in computers and various compact disc formats.

Pink noise
Pink noise has a spectral frequency of 1/f and is found mostly in nature. It is the most natural sounding of the noises. By equalizing the sounds, you can generate rainfall, waterfalls, wind, rushing river, and other natural sounds. Pink noise is exactly between brown and white noise (hence, some people used to call it tan noise). It is neither random nor predictable; it is fractal-like when viewed. When zoomed in, the pattern looks identical to when zoomed out, except at a lower amplitude.

Pitch bender
This effect varies the pitch of the source audio over time. You can sometimes use a graph to "draw" a tempo to create smooth tempo changes or other effects, such as that of a record or a tape speeding up or slowing down.

Pitch correction
Most Pitch Correction effects provide two ways to make pitch adjustments for monophonic instruments or voices. Automatic mode analyzes the audio content and automatically corrects the pitch based on the key you define, without your having to analyze each note.

Pitch shifter
A pitch shifter lets you transpose a sound with or without changing it's length. The earlier versions like the famous Harmonizer from Eventide didn't let you preserve the formants of the sound and if you changed the pitch more than 2 or 3 halftones upwards it sounded like Mickey Mouse. Modern pitch shifters let you preserve the formants in a sound to avoid that effect.

Quick Time
A video and animation system developed by Apple Computer. QuickTime is built into the Macintosh operating system and is used by most Mac applications that include video or animation.

RAW
This format is simply the PCM dump of all data for the wave. No header information is contained in the file. For this reason, you must select the sample rate, resolution, and number of channels upon opening the file.

Real Audio
An audio format that allows a user to hear streaming audio files in real time over the Internet as opposed to waiting for an audio file to download before hearing it.

Real Video
An video format that allows a user to watch streaming video files in real time over the Internet as opposed to waiting for a video file to download before watching it.

Red book
The Red Book Standard was developed to define specifications for producing audio CDs, and is the first of the book standards. The Red Book Standard contains specifications on size of the media, maximum recordable area, tracking information, etc. All subsequent books (Orange Book multisession specifications for CD-R/RW, Yellow Book for data, White book for CD-Interactive, etc.) are based on the physical specifications contained in the Red Book.

Render
Computing the final file in a sound editor or graphics program .

Rubber band curves
Also called envelopes. Curves used to automate volume, pan, effect parameters, tempo, etc... You can create dragging points and move them or shift the whole graph up and down.

Sample
A digital recording of a sound, often a single note, or perhaps several bars of a song, the length only restricted by the memory of the system. Once the sound is "sampled" or digitized, it can be manipulated. The sample can be trimmed, looped, pitch-shifted, reversed, slowed-down or speeded-up, and altered in a myriad of ways.

Sample-rate
The sampling rate determines the frequency range of an audio file. The higher the sampling rate, the closer the shape of the digital waveform will be to that of the original analog waveform. Low sampling rates limit the range of frequencies that can be recorded, which can result in a recording that poorly represents the original sound.
Scrubbing
Ability to move forward/reverse in the audio while listening to the audio. Similar to cueing during wind/rewind on analogue recorders.

SCSI
Small Computer System Interface. Bidirectional, parallel interface to connect up to 7 (15 with wide SCSI) external devices to a computer.

Spectrum analyzer
An instrument or software which displays the frequency spectrum of a sound signal. The frequency spectrum is sometimes divided into bands (usually 10, 15 or 30 bands).

Track ID
A CD can contain up to 99 track IDs that identify the start of audio tracks on a CD. If you need more identification points on your CD you have to use Index points. A track can be a minimum of 4 seconds long (600 sectors).

Threshold
A point at which an effect can be seen. For example, the threshold of a compressor is the minimum voltage that must be present bat the input before any compression occurs.

Trimming/cropping
Cutting down a sound file to the desired size or shape.

Tube emulation
When a tube is driven into saturation, it reacts by producing mostly harmonic overtones. This is usually rather pleasant to the ear compared to clipping of transistors or even digital clipping, which reacts by producing mainly disharmonic overtones. This effect is used by guitar amplifiers or similar equipment and can be emulated by software, mostly Plug-Ins.

WAV
Waveform Audio; uncompressed file format was developed jointly by Microsoft and IBM as the standard format for sound on PCs. WAV sound files end with a .wav extension and can be played by nearly all Windows applications that support sound.

Waveform
A waveform is the visual representation of wave-like phenomena, such as sound or light. For example, when the amplitude of sound pressure is graphed over time, pressure variations usually form a smooth waveform.