Definition of Terms ADAT – A digital 8-track tape deck manufactured by Alesis Corporation that is very popular in recording studios. ADC – (analog-to-digital converter) The hardware that converts an analog audio or video signal into a digital signal that you can process with a computer. Aliasing – Noise that occurs when a high frequency sound exceeds the Nyquist Frequency for a given sample rate. Most analog-to-digital converters prevent aliasing by filtering out sounds above the Nyquist Frequency.
Amplitude – Amplitude represents the volume of an audio signal.A waveform’s amplitude is measured by its distance from the center line, which represents an amplitude of 0. There are different standards for measuring amplitude, but the decibel (dB) is the most common.
Analog Recording – Traditional audio recording with devices such as magnetic tape machines and vinyl records. Analog audio recording consists of a continuous curve, as opposed to digital recording, which consists of discrete samples. ASIO – (Audio Stream In/Out) A standard for low-latency drivers, created by Steinberg Media Technologies. Attack – The first part of the sound that you hear.Some sounds (like pianos and drums) have a very fast attack; the loudest portion of the sound occurs very quickly. A sound with a slow attack rate (such as a soft string section) slowly increases in volume. Attenuate – To reduce volume or signal level.
Automation – The process of recording volume, pan, and effects changes during a mix, and perfectly reproducing those changes every time a mix plays. Band Pass Filter – A filter that allows some audio frequencies to pass through unchanged. Beats Per Minute (bpm) – Musical tempo, which is defined by the number of beats that occur every 60 seconds.
Bit Depth (or bit resolution) – The number of bits used to represent audio amplitude. For example, 8-bit resolution provides 256 possible amplitude levels and a 48 dB dynamic range; 16-bit resolution provides 65,536 levels and a 96 dB range. Adobe Audition supports up to 32-bit resolution with 4,294,967,296 possible levels. For the best audio quality, remain at 32-bit resolution while transforming audio in Adobe Audition, and then convert to a lower bit depth for output. Brown Noise – Brown noise has a spectral frequency of 1/f^2, so it emphasizes low-frequency components, resulting in thunder- and waterfall-like sounds.Brown noise follows a Brownian motion curve, in which each sample in a waveform contains a mixture of predefined and random frequency components. Bus – In hardware mixers, a channel that lets you combine several other channels and output them together.
In Adobe Audition’s Multitrack View, you can similarly use software buses to combine several tracks. Click Track – An audio track comprised of clicks that occur on the beat, like a metronome. Click tracks are often used at the beginning of a session to provide timing information for musicians and then removed from the session before mixing down.Clip – A visual representation of individual audio, video, or MIDI files in Adobe Audition’s Multitrack View.
Clipping – In digital audio, distortion that occurs when the amplitude of a signal exceeds the maximum level for the current bit depth (for example, 256 in 8-bit audio). Visually, clipped audio produces broad flat areas at the top of a waveform. If you experience clipping, lower the recording input or the source output levels. Codec – (compressor/decompressor) An abbreviation for the data compression schemes used by the ACM, AVI, MPEG, and QuickTime formats and the analog-to-digital converters on some sound cards.
Note that codecs only compress file size; to compress audio amplitude, apply a compressor effect. ) Compressor – An effect that reduces dynamic range by lowering amplitude when an audio signal rises above a specified threshold. For example, a compressor can compensate for variations in level caused by a vocalist who occasionally moves away from a microphone. Or, during mastering, a compressor can produce consistent levels for full program material, providing a solid, professional sound for web, video, and radio presentations.Adobe Audition provides two compressor effects: Dynamics Processing and Multiband Compressor.
Crossfade – A fade from one audio clip or track to another. Crosstalk – Undesired leakage of audio from one track to another, a common problem with analog tape. Crosstalk is impossible in Adobe Audition because each track is stored as a separate digital audio file. DAC – (digital-to-analog converter) The hardware that converts a digital audio or video signal into an analog signal that you can play through amplifiers and speakers.DAT – (digital audio tape) A standard two-track digital audio tape format. DAT tapes are sampled at 16 and 24 bits, and 32,000, 44,100, and 48,000 samples per second.
(The latter is often described as DAT quality. ) DAW – (digital audio workstation) A computer system used to edit, process, or mix audio. dBFS – Decibels below full scale in digital audio.
The maximum possible amplitude is 0 dBFS; all amplitudes below that are expressed as negative numbers. A given dBFS value does not directly correspond to the original sound pressure level measured in acoustic dB.DC Offset – Some sound cards record with a slight DC offset, in which direct current is introduced into the signal, causing the center of the waveform to be offset from the zero point (the center line in the waveform display). DC offset can cause a click or pop at the beginning and end of a file. To compensate for DC Offset, use the DC Bias Adjust setting provided by the Amplify command.
Decibel (dB) – In audio, the decibel (dB) is a logarithmic unit of measurement used for amplitude. Delay – A time-shifted signal that you can mix with the original, nondelayed signal to provide a fuller sound or create echo effects.Adobe Audition offers a variety of delay effects such as Reverb, Chorus, and Echo. Destructive Editing – Editing (such as cutting and pasting, or effects processing) that changes the original audio data. For example, in destructive editing, a change in audio volume alters the amplitude of the original audio file. In Adobe Audition, Edit View is a destructive editing environment; however, edits do not permanently change audio until you save a file. DirectX – A development platform designed by Microsoft that provides an open standard for audio plug-ins.Plug-ins based on this standard can be used by any application that supports DirectX, such as Adobe Audition.
Dithering – Adds small amounts of noise to a digital signal so that very quiet audio remains audible when you convert from a high bit resolution to a lower one (for example, when converting from 32-bit to 16-bit). Without dithering, quiet audio passages such as long reverb tails may be abruptly truncated. Dry – Describes an audio signal without any signal processing such as reverb; the opposite of wet. DSP – (digital signal processing) The process of transforming a digital audio signal by using complex algorithms.Examples include filtering with equalizers, and effects processing with reverbs and delays. DVD – A storage medium similar to a CD, but with much higher bandwidth and storage capabilities. Audio in DVD movies generally uses a 96-kHz sample rate and a 24 bit depth.
Dynamic Range – Audio amplitude range, from quietest troughs to loudest peaks. Equalization (EQ) – The process of increasing or decreasing the amplitude of specific audio frequencies relative to the amplitude of other audio frequencies. Expander – Increases dynamic range by lowering amplitude when an audio signal falls below a specified threshold (the opposite of a compressor).For example, an expander can be used to lower the level of background noise that becomes audible when a musician stops playing. FFT – (Fast Fourier Transform) An algorithm based on Fourier Theory that Adobe Audition uses for filtering, Spectral View, and Frequency Analysis features. Fourier Theory states that any waveform consists of an infinite sum of sine and cosine functions, allowing frequency and amplitude to be quickly analyzed. Higher FFT sizes create more precise results but take longer to process. Frequency – Describes the rate at which a sound wave vibrates, measured in cycles per second, or hertz (Hz).
A cycle consists of a single, repeated sequence of pressure changes, from zero pressure, to high pressure, to low pressure, and back to zero. A sound wave’s frequency determines its pitch: high frequency equals high pitch, and low frequency equals low pitch. Hertz (Hz) – Cycles per second. A unit of measurement that describes the frequency of a sound. Interpolate – To estimate the values of data points between known data points. Interpolation is used when new data must be generated to fill in areas where values are unknown. Latency – Measures the delay between user input and sound output from a computer.If latency is high, it produces an audible echo during recording, disrupting timing for musicians.
To reduce latency, use sound cards with ASIO drivers. Limiter – A signal processor that prevents audio from clipping. If the input signal exceeds the specified threshold level, the output level remains constant even if the input increases in volume. Loop – An audio file that contains tempo and pitch information, allowing it to match the tempo and pitch of other loops in a multitrack session. You can repeat a loop-enabled clip infinitely by simply dragging its bottom right corner.Mastering – The process of finalizing audio for a specific medium, such as the web or an audio CD. Mastering consists of several processing phases, with equalization and compression phases being the most essential. You can master audio files either individually or in groups.
Collectively mastering groups of files is particularly important if the destination medium is audio CD. MIDI – Musical Instrument Digital Interface, a method of communicating performance instructions from one piece of software or hardware to another. MIDI can simply relay musical notes, or it can transmit detailed information about timing, synthesizer patches, and such.Windows transmits MIDI information internally between applications; to transmit MIDI information between your computer and external devices such as MIDI keyboards, you must use a hardware MIDI interface (for example, the MIDI In port of a sound card). MIDI Timecode (MTC) – A method of sending timing information between MIDI-capable devices.
For example, you can convert SMPTE timecode to MTC to synchronize Adobe Audition’s transport controls with a video or audio tape deck. MIDI Trigger – An Adobe Audition shortcut triggered by a MIDI event, such as Note On.You can send MIDI events to any device capable of issuing a MIDI command, such as MIDI keyboards and sequencers.
Millisecond (ms) – One thousandth of a second. (There are 1000 milliseconds in a second. ) Miniplug – A common name for 1/8-inch plugs and jacks, sometimes known as minijacks. On the most common sound cards, miniplug jacks provide analog audio inputs and outputs.
Mix (or mix down) – To combine multiple audio sources or tracks and output them together. Though mixes are typically output to a stereo pair of channels, they can be directed to any number of channels (for example, one channel for mono, or six channels for surround-sound).Mono – A monophonic signal, which contains only one sound source. MP3 – MP3 is an audio-specific format that was designed by the Moving Picture Experts Group as part of its MPEG-1 standard and later extended in MPEG-2 standard.
Noise Gate – A special type of expander that reduces or eliminates noise by greatly lowering signal levels that fall below a specified threshold. Noise gates are often configured to totally eliminate background noise during musical pauses. You can also use these gates to silence pauses in speech. Noise Shaping – A technique that shifts the frequency of dithering noise to minimize its audibility.Nondestructive Editing – Nondestructive edits don’t alter a sound file on disk in any way. For example, nondestructive volume changes do not alter the amplitude of a waveform, but instead simply instruct an audio application to play the waveform at higher volume. In Adobe Audition, Multitrack View is a nondestructive editing environment.
Normalize – To adjust the highest peak of a waveform so it nearly reaches the digital maximum, 0 dBFS, thereby raising or lowering all other peaks accordingly. Typically, audio is normalized to 100% to achieve maximum volume, but Adobe Audition lets you normalize to any percentage.Nyquist Frequency – A frequency equal to half the current sample rate, which determines the highest reproducible audio frequency for that rate. For example, audio CDs use a sample rate of 44,100 Hz because the resulting Nyquist frequency is 22,050 Hz—just above the limit of human hearing, 20,000 Hz. For the best audio quality, record and edit at higher sample rates and then convert down if needed.
Offline Processing – Intensive effects processing that requires dedicated computer power, briefly preventing you from editing audio. Order – A value that determines the slope of an audio filter.First-order filters attenuate an additional 6 dB per octave, second-order filters attenuate 12 dB, third-order filters 18 dB, and so on. PCM – (pulse code modulation) PCM is the standard method used to digitally encode audio and is the basic, uncompressed data format used in file formats such as WAV and AIFF. Phase – The position of a sound wave relative to other sound waves.
As a sound wave travels through the air, it compresses and expands air molecules in peaks and troughs, much like an ocean wave. In the waveform display, peaks appear above the center line, troughs appear below.If two channels of a stereo waveform are exactly opposite in phase, they will cancel each other out. More common, however, are slightly out-of-phase waves, which have misaligned peaks and troughs, resulting in duller sound. Pink Noise – Noise with a spectral frequency of 1/f, producing the most natural-sounding generated noise.
By equalizing pink noise, you can simulate rainfall, waterfalls, wind, a rushing river, and other natural sounds. On the audio spectrum, pink noise falls exactly between brown and white noise. Plug-In – A software component that you can add to another piece of software to increase its functionality.Adobe Audition supports third-party VST and DirectX audio plug-ins, which seamlessly integrate into Adobe Audition’s interface. Punch In – A recording method used to insert a new recording into a specific region of an existing waveform, usually to replace an undesirable section.
Adobe Audition supports punch-in recording in Multitrack View and allows for multiple takes; you can repeatedly record over the original material and later choose the best performance. Quantization – A process that occurs when an analog waveform is converted to digital data and becomes a series of samples.Quantization noise is introduced as some samples are shifted to quantization levels allowed by the current bit depth. This noise is highest at low bit depths, where it can particularly affect low amplitude sounds.
RCA cable – Sometimes called a phono cable, RCA cables have RCA plugs or jacks at either end and are normally used to connect stereo system components, such as receivers, CD players, and cassette decks. Real Time – In computer-based audio, real time refers to functions that immediately respond to user input. Note, however, that system speed ultimately determines processing time.Adobe Audition provides real-time mixing and effects in Multitrack View, and real-time previews in Edit View. Resample – To convert a sound file to a different sample rate and bit depth. Reverb – The reverberant sound produced by an acoustic space, such as a room or concert hall. Reverb consists of dense, discrete echoes that arrive at the ear so rapidly that the brain can’t separate them. Adobe Audition offers three reverb effects: Studio Reverb, Reverb, and Full Reverb.
ReWire – A technology for synchronizing audio applications created by Propellerhead Software.RMS – (Root-mean-square) A mathematical formula used to determine the average amplitude of an audio selection. RMS amplitude reflects perceived loudness better than peak amplitude. S/N Ratio – Signal-to-noise ratio describes the difference between the highest signal level before distortion and the average level of the noise floor. In most analog systems, such as microphone preamps, the S/N ratio is around 92 dB. Sample – A digital snapshot of an audio waveform at a particular point in time.
In digital audio, a series of numeric samples reproduces an entire waveform, with higher sample rates producing increased frequency response. Note that musical samplers use the term sample to describe a digital recording, rather than a digital snapshot. ) Sample Rate – The number of samples per second. Higher sample rates produce increased frequency response but require more disk space.
To reproduce a given audio frequency, the sample rate must be at least double that frequency. Sampler – A musical device that records and plays digital sounds (known as samples in this context) and lets you edit and store those sounds. Sequencer – A programmable piece of software or hardware that can record and play a sequence of musical events, such as samples, pitches, and rests.Most modern sequencers are MIDI-based. Session – A multitrack project in Adobe Audition. Session files are stored with the extension . ses and contain details such as mixing and effects settings.
Session files don’t contain audio data; instead they contain pathnames pointing to the sound files used in the session. SMPTE Timecode – (Society of Motion Picture and Television Engineers timecode) A timing reference used to synchronize two devices. SMPTE timecode is divided into hours, minutes, seconds, and frames. Sound Card – A hardware device that lets your computer play and record audio. Sound Wave – A wave of air molecules.
Humans can hear sound waves with frequencies of 20 to 20,000 Hz. Spectral Editing – Editing audio using a display that visually represents audio frequencies. In spectral displays, bass frequencies appear at the bottom, treble at the top. Volume is represented by color intensity.
In Adobe Audition, you perform spectral editing to remove noise or process specific frequency ranges. Stereo – A signal with a left and right channel, allowing for spatial placement of sounds. Stripe – To copy SMPTE timecode to a single track of a multitrack tape so remaining tracks can be synchronized with other devices.Tempo – The rhythmic speed of music, normally measured in beats per minute.
Timecode – An audio or digital signal that synchronizes time between multiple devices. The most common forms are SMPTE and MIDI timecode. Unity Gain – An amplification level that precisely corresponds to the input signal level, without amplifying or lowering it.
(Note that audio hardware operates at two line levels: –10 dBV for consumer equipment, and +4 dBu for professional. If these two hardware types are connected, unity gain will result in a lowered input for consumer equipment, and a raised input for professional. )VST – Virtual Studio Technology, a plug-in format compatible with a wide variety of audio software. VST plug-ins provide audio effects such as compression and reverb; VSTi plug-ins provide virtual instruments such as samplers and synthesizers. WAV – AVE or WAV, short for Waveform Audio File Format (also, but rarely, named, Audio for Windows) is a Microsoft and IBM audio file format standard for storing an audio bit stream on PCs.
Waveform – A term that describes the visual representation of an audio signal, displayed as amplitude across time in Adobe Audition. (In acoustics, waveform refers to a sound wave of a specific frequency. Wet – Describes an audio signal that includes signal processing such as reverb; the opposite of dry.
White Noise – White noise has a spectral frequency of 1, so equal proportions of all frequencies are present. Because more individual frequencies exist in the upper ranges of human hearing, white noise sounds very hissy. Adobe Audition generates white noise by choosing random values for each sample.
Zero Crossing – A point in time where a waveform crosses the zero amplitude line. To make edits sound smoother, place them at zero-crossing points, thus avoiding abrupt changes in amplitude that cause pops and clicks.