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Describes any unpleasant, objectionable or unintended sound frequencies present in the audio signal. All electronic equipment produces some type of noise, which may be described as a hiss or buzz that can be heard during quiet or otherwise silent passages. (See also “Noise Floor.”) Bad connections, improper grounding, radio interference and other issues can also cause introduce noise into the signal. Engineers may also deliberately run a noise signal through a sound system for testing purposes. (See also “White Noise, “Pink Noise.”)
The level of the noise present below the audio signal, measured in dB. Every electronic device emits a minimum level of noise, even when no audio is traveling through it; this is described as its noise floor. Generally speaking, the lower the noise floor in these devices, the higher the quality of the device. The noise floor also translates to the recorded signal; the noise floor of a recording is the sum of all the noise generated by connected devices. The objective is always to keep the noise floor as low as possible.
A gate that is used reduce audible noise by automatically turning off an audio channel when the signal is not present.
Any of a number of processes to remove noise from a signal, device or system.
A feature in recording systems (most common in Digital Audio Workstations, or DAWs) in which the original signal or content stays intact while edits are performed, allowing the engineer to revert to the original version at any time. (Sometimes also called “Nonlinear editing.”)
To apply a fixed amount of gain to audio so that the highest peak is set at the highest acceptable recording level.
Describes the configuration within a patch bay in which the jacks form a connected pathway until a patch cord is inserted to change the path. When a patch bay is “full-normalled,” the connection is altered by inserting a cord into either the input or output side; when it is “half-normalled,” the path changes only when a cord is plugged into the input. “Non-normalled” or “open” means there are no internal connections, and each input sends the signal through its corresponding output.
A narrow band of audio frequencies.
A band stop filter set to reject frequencies within a very narrow band. So called because the attenuated frequency band looks like a “notch” in the spectrum it is displayed visually (for example, in an EQ plugin). (See also “Band Stop Filter.”)
See “Nanowebers per Meter.”
One half byte of computer data, or 4 bits.
In digital recording, the highest frequency that can be recorded and reproduced properly, equivalent to a one-half the sampling rate. (For example, with the common sampling rate of 44,100 kHz per second, the Nyquist frequency would be 22,050 kHz.) Aliasing begins to occur with frequencies that exceed this threshold. (See also “Aliasing.”)
The lowest sampling rate that can be used to record and reproduce a given audio signal, equivalent to twice the highest frequency. If the highest frequency found in an analog signal or sound is 18,000 kHz, theoretically the signal must be sampled at a minimum of 36,000 kHz per second—otherwise, the signal is considered to be undersampled and aliasing will occur. This is essentially the inverse principle of the Nyquist Frequency. (NOTE: the sample rate of 44,100 kHz/second is considered the standard sample rate because it easily covers the upper range of human hearing, which is about 20,000 kHz.)
An interval or difference of pitch of 12 half-steps. In our standard tuning system, the higher note in an octave is exactly double the frequency of the lower note.