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Audio Glossary

Video Glossary

Permanent link to this article: http://ohda.matrix.msu.edu/gettingstarted/glossary/audioglossary/

16-bit/44.1 kHz

16-bit/44.1 kHz: Refers to recording settings for digital audio at a bit depth of 16 and a sample rate of 44.1 kHz.  This is commonly referred to as “CD Quality” and is the recommended minimum recording quality for oral history. [ Audio Glossary ] [ Archive Glossary ] Tweet

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24-bit/96 kHz

24-bit/96 kHz: Refers to recording settings for digital audio at a bit depth of 24 bit and a sample rate of 96 kHz. This is the current recommended standard for recording digital audio or digitizing analog audio. [ Audio Glossary ] [ Archive Glossary ] Tweet

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AES-EBU

AES/EBU: Digital audio standard known as AES3, usually associated with professional level transfer (from where to where) of digital audio in real time. Developed by a collaboration between the Audio Engineering Society (AES) and the European Broadcasting Union (EBU).  At this time, AES/EBU is not associated with most portable field recorders but can be utilized in …

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Amplify

Amplify: Increase the strength of the audio signal. [ Audio Glossary ] [ Video Glossary ] Tweet

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Analog

Analog: In the context of audio, “Analog” refers to the method of representing a sound as a continuous wave with voltage fluctuations that are “analogous” to the pressure fluctuations of the sound wave. Analog fluctuations are infinitely varying. Alternatively, digital audio captures a stream of fluctuations at discrete intervals and represents the sound using numbers that …

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Analog to Digital Converter— (ADC, A/D or A to D)

Analog to Digital Converter— (ADC, A/D or A to D) : Device that converts analog signals to digital. This involves a conversion of the voltages representing the original pressure waves into discrete digital numbers that can be read by computer or digital audio device. To achieve archival-quality conversion (digitization), practitioners should seek out the highest-quality …

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ASIO

ASIO: Computers need to take audio in and send it out. On the audio card, ASIO is software that controls audio stream input/output. So ASIO is a computer driver for digital audio, originally developed by a German company, Steinberg. The ASIO protocol is usually associated with higher-end audio hardware. It enables software to directly communicate …

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Attenuate or Attenuation

Attenuate or Attenuation: A decrease in the level of a signal (contrast amplify). Why would you do this? A microphone attenuator reduces the output of a microphone and protects the inputs of the recorder from becoming overloaded and therefore distorted.  Microphone attenuators appear on recorders, usually with a variety of Decibel settings. Standard attenuators on …

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Audio Interchange File Format

Audio Interchange File Format (AIFF): A relatively uncommon digital audio data file format. The format was developed by Apple Computer. Most portable field recorders record their signals as .wav files. Professional level digital audio editing software packages should include AIFF compatibility however. Both AIFF and .wav files utilize compression; AIFF uses uncompressed pulse code modulation or PCM. …

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Audio Editing Software

Audio Editing Software: Computer software designed for capturing and manipulating digital audio. This can involve editing for production, digital signal processing of the audio recording, saving the file in a different format, converting from stereo to mono, compressing a signal, changing the sample rate or bit depth of the data file. Stereo editing software can only …

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Automatic Level Control (ALC) /Automatic Gain Control (AGC)

Automatic Level Control (ALC) /Automatic Gain Control (AGC): A circuit inserted in the preamplification stage of the recorder that quickly and automatically adjusts the recording levels to adapt to changes in the audio source signal. This function will work instead of the manual level adjustment capability and will boost a lower end signal as well as …

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Automatic Speech Recognition (ASR)

Automatic Speech Recognition (ASR): Computer software and hardware that translates spoken audio into text. In an oral history context, this would automate the transcribing process. Research is continually improving accuracy. [ Audio Glossary ] [ Archive Glossary ] Tweet

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Balanced Inputs/Outputs

Balanced Inputs/Outputs: A protocol for connecting analog audio devices using impedance-balanced cables. This protocol is usually associated with professional-level audio equipment and allows for longer cable lengths as well as reducing the addition of external noise to the signal. Balanced cables have either XLR or TRS plugs. Professional-level digitization will usually involve balanced outputs on the …

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Boomy

“Boomy”: Refers to audio that is accentuating the lower frequencies of a signal too much. Essentially means that the bass signal in a piece of audio is too powerful, either due to the mixing of the actual track being played or the settings on the system it is being played on. [ Audio Glossary ] …

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Bright

“Bright”: Refers to the clarity of the higher frequencies in a recording. The brighter a piece of audio is, the more clear and distinct these higher frequencies are. [ Audio Glossary ] Tweet

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Cardioid Microphone Pattern

Cardioid Microphone Pattern: The heart-shaped area that defines where a cardioid microphone is designed to pick up sound. The cardioid pattern itself is what results from tracing the path of a point on one fixed circle as it rotates around another fixed circle. Used mostly in recording vocals and speech, because the cardioid pattern accepts sound …

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Channel Convert

Channel Convert: A process that converts audio channel configuration. Often this involves converting the configuration from multiple channels to either stereo to mono or converting from mono to stereo. Also can be used to transfer bits of stereo audio from the left channel to the right or the right to the left to create fading …

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Clipping

Clipping: Occurs when the level of sound in an audio track or file is above the highest recording level available. If clipping occurs then it will cause distortion in audio playback. [ Audio Glossary ] [ Video Glossary ] Tweet

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Condenser Microphone

Condenser Microphone: In a condenser microphone, a capacitor is used to sense changes in the distance between two metal plates as the vibrations from a sound source hit them. The changes in distance are measured by the minute fluctuation of an almost constant electric current running between the two metal plates. Since the capacitor requires …

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Digital-to-Analog Converter (DAC)

Digital-to-Analog Converter (DAC): These converters are found in any hardware that plays audio from a digital source, the most common being CD players. Since the data stored on the CD itself is digital and the sound that we hear from the speakers is analog, the DAC has to take the digital information provided from the …

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Digital Audio Workstation (DAW)

Digital Audio Workstation (DAW): A DAW is a system that allows a user to play, record, and edit digital audio. These systems can come both as a computer software program or as an all in one audio workstation, though these have become less popular as personal computers have become more advanced and cost-effective. [ Audio Glossary ] …

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DC Offset

DC Offset: This occurs when an outside source causes the mean value of the amplitude of a waveform to be either higher or lower than zero. When normalized, a waveform with no DC offset will be able to maximize its volume, but if affected by DC offset, it will have lost a variable amount of …

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Decibel (dB)

Decibel (dB): Sound is measured in Decibels, which measures audio intensity. Named after Alexander Graham Bell. Digital recorders measure levels up to 0dB. Levels exceeding 0dB result in clipping and distortion. Good recording levels in an oral history interview will range from -12dB to -6dB, leaving enough headroom for intermittent spikes in levels. [ Audio …

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Digital Audio

Digital Audio: Using digital formats, signals, computers, and networks to create and reproduce sound. Digitization allows for easy storage. It also makes it easier to work audio, since digital systems are not limited by time or amplitude as analog sources are–digital audio breaks down sound from a continuous line of audible information into a segmented, …

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Digital Audio Editing

Digital Audio Editing: A digital audio editor is software that allows a user to visualize (and manipulate) audio files stored on a computer. Changing file formats, increasing or decreasing volume levels, and a myriad of other options are available depending on the software chosen. [ Audio Glossary ] Tweet

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Digital Signal Processing (DSP)

Digital Signal Processing (DSP): This is a blanket term that applies to any alteration of digital data. Analog signal processing has been around for decades in hundreds of applications, but the advent of the digital age has allowed a computer to do far more with signal processing due to the discrete nature of digital data. …

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Digital Signal Processor

Digital Signal Processor: A microchip developed exclusively to handle the mathematically intense operations required by digital signal processing. [ Audio Glossary ] Image Source: http://en.wikipedia.org/wiki/File:Dsp_chip.jpg Tweet

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Directional Microphone

Directional Microphone: These microphones focus their polar pattern (the area they are intended to pick up sound from) in specific ways. They can be bi-directional, i.e. a stereo microphone, which will record to the side, rather than all around the microphone housing. Others include shotgun microphones that are used to focus on specific sounds, while …

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Distortion

Distortion: In audio, distortion is a negative term–unless you play the electric guitar. It refers to any unwanted change to the original waveform due to clipping, compression, aliasing, mixing, modulation, power supply problems, as well as changes during the analog to digital conversion process. [ Audio Glossary ] Tweet

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Dynamic Microphone

Dynamic Microphone: Well suited for onstage environments because they can support levels of high gain before succumbing to feedback, these microphones are popular and relatively inexpensive. Works by harnessing the power of electromagnetic induction. [ Audio Glossary ] Image Source: https://microphones.audiolinks.com/microphones.shtml Tweet

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Dynamic Range

Dynamic Range: The ratio (difference) between the highest and lowest levels of any variable quantity, including sound. [ Audio Glossary ] Tweet

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Electret Condensor Microphone

Electret Condensor Microphone: Works under the same principles as normal condenser microphones, but the electret variety are made with permanently charged material to read sound waves, thus eliminating the need for polarizing voltage. Most of these microphones do require a battery, but the power drain is so minimal that they may have an integrated one …

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Equalization (EQ)

Equalization (EQ): The process of raising or lowering the frequency response attributes of audio through active or passive means. [ Audio Glossary ] Tweet

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Flat Response

Flat Response: Audio systems that can reproduce an original tone without deviating from the original levels of intensity in frequency are said to be capable of Flat Response. [ Audio Glossary ] Tweet

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Frequency

Frequency: The number of occurrences of a repeating event per unit time. [ Audio Glossary ] Tweet

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Gain

Gain: The ability of an electronic circuit to increase the power or amplitude of an electronic signal. In audio, this applies directly to the volume. [ Audio Glossary ] Tweet

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Headroom

Headroom: This is the distance between the highest (or lowest) sound in a recording, and the highest (or lowest) sound the audio system can handle before it starts clipping or distorting sound. [ Audio Glossary ] Image Source: http://en.wikipedia.org/wiki/File:Lindos10.svg Tweet

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Hertz (Hz)

Hertz (Hz): Sounds occur when something, like a violin string, vibrates (goes back and fourth, pushes air around, which goes into ears). One complete back and fourth per second is = to 1 Hertz. Humans can hears sounds that go from about 20 complete vibrations per second (20 hertz) to 20,000 complete vibrations per second …

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High-Pass Filter

High-Pass Filter: Filter that allows high frequencies to pass through, but catches (attenuates) low frequencies at a certain point allowing for the easy elimination of unwanted lower frequency noise. [ Audio Glossary ] Tweet

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Hiss

Hiss: Noise present in many situations that can be reflected in recorded audio. In digital audio, the biggest threat is the hiss that all electric circuits exhibit. This can be audible or not, but always has the ability to ruin a recording. [ Audio Glossary ] Tweet

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Hold Button

Hold Button: Found on most portable devices, especially audio hardware. Use of the hold button will lock all the other buttons so that they won’t be pressed in error. Usually present in slider form, but sometimes as a button itself. [ Audio Glossary ] Image Source: http://www.guru3d.com/article/iriver-h320-20gb-multicodec-jukebox/3 Tweet

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“Hot”

“Hot:” Term generally applied to audio that is very loud or exhibits high, active tendencies when viewed on a level meter. [ Audio Glossary ] Tweet

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Hum

Hum: Sound produced when audio equipment picks up the oscillation of electronic currents from other equipment nearby. The hum is audibly reproduced through speakers. [ Audio Glossary ] Tweet

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Hyper Cardioid Microphone

Hyper Cardioid Microphone: Much the same as a normal cardioid microphone, but features a highly tightened cardioid pattern. This focuses the sensitivity pattern into a tight area to the front of the microphone. [ Audio Glossary ] Image Source: http://en.wikipedia.org/wiki/File:Polar_pattern_hypercardioid.png Tweet

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Internal Microphone

Internal Microphone: Microphone that is housed within audio recording equipment. While convenient, these microphones sometimes come with substantial limits. [ Audio Glossary ] [ Video Glossary ] Tweet

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Key Lock

Key Lock: See Hold Button. [ Audio Glossary ] Tweet

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Kilohertz (kHz)

Kilohertz (kHz): 1,000 Hertz (Hz). Unit of measure for sample rate in digital audio. [ Audio Glossary ] Tweet

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Lapel / Lavalier Microphone

Lapel / Lavalier Microphone: Small dynamic or condenser microphone that is usually clipped to a lapel or shirt to provide convenient recording of speech. Because of the proximity to the sound source, these microphones usually produce a much better signal to noise ratio. [ Audio Glossary ] Image Source: http://www.recording-microphone.com/electret-microphones.php Tweet

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Level Meter

Level Meter: A graphic display, for audio, that shows increasing and decreasing loudness/ volume during recording or playback. Generally it is color-coded and provides a warning when sound levels are peaking. [ Audio Glossary ] [ Video Glossary ] Tweet

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Limiter

Limiter: A limiter creates a ceiling on volume by blocking frequencies over a certain threshold. It can be used during recording to make sure that sound levels do not peak. Essentially I like to think of a limiter as the friend who assists you in not doing something foolish. [ Audio Glossary ] Tweet

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Line Level

Line Level: This describes the signal strength of audio passing between two hardware components, i.e. from a CD player to an audio receiver. [ Audio Glossary ] Tweet

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Low-Pass Filter

Low-Pass Filter: The opposite of a High-Pass Filter. Allows signals of low frequency through while attenuating those of higher frequencies set by the user. [ Audio Glossary ] Tweet

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Marker

Marker: A user-deployable point for quick reference and easy editing in digital audio programs as well as tape decks and CD players. [ Audio Glossary ] Tweet

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Microphone (Mic)

Microphone (Mic): Device to convert acoustic energy (sound waves) into electrical energy. In an oral history context, this is what enables the recording of audio signals. Different microphone types often used in an oral history context include condenser or dynamic microphones. Microphones contain patterns for how they “listen” which include cardioid (directional), shotgun (really directional) …

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Mid-Side Recording

Mid-Side Recording: Recording technique utilizing one microphone pointed directly at the speaker (mid) and one at a 90-degree angle (side). The two audio channels are then mixed into a traditional stereo image. [ Audio Glossary ] Image Source: http://www.uaudio.com/blog/mid-side-mic-recording/ Tweet

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Mini Jack

Mini Jack: See TRS (Tip, Ring, Sleeve) Connector. [ Audio Glossary ] Image Source: http://en.wikipedia.org/wiki/File:Audio-TRS-Mini-Plug.jpg Tweet

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Monitor (Audio levels)

Monitor (Audio Levels): Maintaining watch over sound levels when recording. The dynamic nature of human vocalization makes monitoring incredibly important. [ Audio Glossary ] [ Video Glossary ] Tweet

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Monitor (speaker)

Monitor (speaker): A speaker used in a studio for hearing the sound that is produced. Studio monitors tend to produce a flat response and ensures that the audio heard by the user through the monitors is as close to the actual sound. [ Audio Glossary ] Image Source: http://ak.buy.com/PI/0/500/210558072.jpg Tweet

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Mono (Monaural)

Mono (Monaural): Used to describe the recording of single channel audio. Most recorders today have the ability to record stereo, which mixes two channels of audio. Single channel audio contains ½ the data as stereo audio and is therefore ½ the file size of a stereo file containing the same recording time. [ Audio Glossary ] …

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MP3 (MPEG Audio Layer III)

MP3 (MPEG Audio Layer III): A standard for encoding digital audio; it uses lossy compression. MP3 uses psycho-acoustic principles to identify unnecessary and imperceptible information that is discarded, thus yielding a smaller file size. Commonly associated with downloadable streaming audio, it is not recommended as a recording or preservation format. [ Audio Glossary ] Tweet

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“Muddy”

“Muddy”: Describes poorly-defined sound quality where all the frequencies tend to run together. [ Audio Glossary ] Tweet

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Noise Floor

Noise Floor: A background sound present when no direct input (like a speaker) is received by the system. Usually this is noise created by the audio system itself, by any number of mechanical and electrical systems that hum and buzz and whir. Typically, inexpensive recorders usually have a higher noise floor than more expensive, professional level counterparts. …

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Normalize

Normalize: Act of increasing volume to allow the highest-level sample in a file to reach the top of a user-defined limit. This ensures that the file will utilize the as much dynamic range as possible. [ Audio Glossary ] Tweet

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Nyquist Theorem (The Sampling Theorem)

Nyquist Theorem (The Sampling Theorem – pretty advanced, don’t sweat it if it seems too complex): During analog-to-digital conversion, the maximum frequency that can be represented by a digital audio source equals half the sample rate used to capture the analog audio. If human hearing is only capable of perceiving 22.5 kilohertz, the sample rate must …

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Pan

Pan: A process for moving a mono (one track) sound signal across stereo (two track) or other multi-channel speakers. [ Audio Glossary ] Tweet

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Pause

Pause: Control that stops audio playback but allows for continuation at the exact point the pause occurred. Important in digital recording as pressing stop while recording will usually create a whole new file, but pause will only stop the recording at a certain point. [ Audio Glossary ] Tweet

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Peak Levels

Peak Levels: See Permitted Maximum Level (PML). [ Audio Glossary ] Tweet

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Permitted Maximum Level (PML)

Permitted Maximum Level (PML): Highest volume a program or piece of hardware can accommodate without resulting in distortion or “clipping.” [ Audio Glossary ] Tweet

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Phantom Power

Phantom Power: Used to send electrical power from the recorder through the microphone cable to a condenser microphone–which requires Phantom Power to operate. True Phantom Power is signified by 48 volts and is provided by the recorder when enabled. [ Audio Glossary ] Tweet

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Polar Pattern (microphones)

Polar Pattern (microphones): Refers to the sensitivity of a microphone to sound coming from a given direction. Common patterns include Cardioid, Omnidirectional, and Shotgun patterns. [ Audio Glossary ] Omnidirectional Subcardioid Cardioid Supercardioid Bi-directional or Figure of 8 Hypercardioid Shotgun Images: http://en.wikipedia.org/wiki/Microphone     Tweet

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Preamplifier (mic pre)

Preamplifier (mic pre): An audio technology on recorders with microphone inputs that boosts the analog audio signal from the microphone enabling the recorder to record the audio signal. Lower quality microphone preamps will add noise as it boosts the signal and are found on many lower end recorders. Higher quality microphone preamps add far less noise …

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Pulse Code Modulation

Pulse Code Modulation: Most portable field recorders and a/d converters utilize a representation called Pulse Code Modulation (PCM) for digital conversion of an uncompressed analog signal. This digital data is then saved as a data file (either .wav or .aif). [ Audio Glossary ] Tweet

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Quantization

Quantization: The process of assigning approximate integer values to analog measurements. This process occurs every time that an analog file of any type is turned into a digital one. As far as audio recording goes, the higher the quality of the digital recording, the greater the number of integers used in the approximation, which results …

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Quantization Noise

Quantization Noise: This is the hiss-like noise that results from Quantization during an analog to digital conversion. A result of all digital recordings because they are based off of approximations of the original analog audio values, not exact copies. The higher the quality of a recording, the less noise present in playback. [ Audio Glossary …

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Quarter Inch Input

Quarter Inch Input: A common TRS connector commonly used for applications ranging from headphones to musical instruments to microphones. [ Audio Glossary ] Image Source: https://www.audiolinks.com/NLimages/Quarter_inch_cable.jpg Tweet

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Record Level

Record Level: The record level refers to the current volume of an incoming audio signal. Usually, physically represented on a level meter. [ Audio Glossary ] Tweet

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Record Pause

Record Pause: Pressing the pause button during recording on most players will allow the user to resume recording right where he or she left off, rather than having to stop and then create another file. [ Audio Glossary ] Tweet

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Resample

Resample: A process by which a sound file is sampled at a rate different than that which it was originally recorded. When dealing with resampling it is always best to make your original recordings at the highest possible bit and sample rates, and then to downsize these files later on if need be. While moving …

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Sample Rate

Sample Rate: Refers to the number of samples per second (of the interviewees responses) in a given digital audio file. The higher the sample rate the greater the sound quality, but the larger the size of the file. [ Audio Glossary ] Tweet

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Shotgun Microphone

Shotgun Microphone: A highly directional microphone, focusing almost the entirety of its Polar Pattern directly in front of the microphone. [ Audio Glossary ] Images: http://en.wikipedia.org/wiki/File:Shotgun_microphone.jpg http://en.wikipedia.org/wiki/File:Polar_pattern_directional.png Tweet

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Signal-to-Noise Ratio (SNR)

Signal-to-Noise Ratio (SNR): Refers to the ratio between a recorded signal and the noise levels associated with it. Think of a conversation (signal) at a cocktail party (noise). The higher the signal-to-noise ratio the better the quality of the audio. [ Audio Glossary ] Tweet

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Sound Card

Sound Card: Sound cards are found in computers and allow 1) audio from outside the computer to be transferred in, 3) audio from the computer to be transferred out, and 3) audio created in the computer (by the sound card) to be heard via speakers or headphones. They have become less and less popular in …

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S/PDIF

S/PDIF: A standard developed by Sony and Phillips to move digital audio signals from one place to another. Generally uses coaxial or fiber optic cable. [ Audio Glossary ] Tweet

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Stereo

Stereo: Refers to audio in which the sound has been separated into two or more distinct channels. [ Audio Glossary ] Tweet

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Stereo Microphone

Stereo Microphone: Actually two microphones in one housing, this configuration is well suited for interview recording as it will separate the interviewer and interviewee between audio channels when placed correctly between them. [ Audio Glossary ] Tweet

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Threshold

Threshold: Refers to a level where a signal processor will begin to act on a signal. Thresholds are set at different levels depending on the application, i.e. a high-pass filter would attenuate sounds below a certain threshold. It can be used to screen out background noise. [ Audio Glossary ] Tweet

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Transducer

Transducer: the conversion of acoustical energy (sound waves) into electrical energy. A microphone is a transducer. [ Audio Glossary ] Tweet

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Transparency

Transparency: An option typically associated with higher-end preamps which boosts audio signals without adding significant noise. [ Audio Glossary ] Tweet

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TRS (Tip Ring Sleeve) Connector

TRS (Tip Ring Sleeve) Connector: These are the typical connections for audio equipment, including microphones and headphones. They come in three different sizes: 3/32″, 1/8″ and 1/4″. [ Audio Glossary ] Image Source: http://en.wikipedia.org/wiki/File:Photo-audiojacks.jpg Tweet

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Uncompressed Audio

Uncompressed Audio: This refers to audio that has had no compression applied to it and is therefore as close to the original sound as possible, though still affected by the sample and bit rate of the recording. The most common format is the .wav. [ Audio Glossary ] Tweet

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Universal Serial Bus (USB)

Universal Serial Bus (USB): A connection standard for connecting hardware to a computer. Allows for hot-swappable connectivity, where an item can be plugged in or unplugged without turning the host computer on and off again. Originally transferred data at 12Mbit/s, but now transfers data at a rate of 480Mbit/s with the 2.0 High-Speed standard. Theoretically …

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Volume

Volume: Standard term for the loudness of an audible sound. [ Audio Glossary ] Tweet

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“Warmth”

“Warmth”: A term that describes the sounds resulting from the 150-400Hz range. [ Audio Glossary ] Tweet

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WAV (.wav)

WAV (.wav): File standard developed by Microsoft and IBM. Most common of the uncompressed audio file formats. [ Audio Glossary ] Tweet

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