A Noise Gate is an electronic device or software logic that is used to control the volume of an audio signal. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation They are commonly used in the recording studio and sound reinforcement. A recording studio is a facility for sound recording. Ideally the space is specially designed by an acoustician to achieve the desired acoustic properties (sound A sound reinforcement system is an arrangement of Microphones electronic Signal processors Amplifiers and Loudspeakers that makes live or pre-recorded Small portable units are also used by rock musicians to control unwanted noise from their amplification systems. Band-limited noise gates are also used to eliminate background noise from audio recordings by eliminating frequency bands that contain only static. Frequency is a measure of the number of occurrences of a repeating event per unit Time.
In its most simple form, a noise gate allows a signal to pass through only when it is above a set threshold: the gate is open. If the signal falls below the threshold no signal is allowed to pass: the gate is closed. A noise gate is used when the level of the 'signal' is above the level of the 'noise'. is a one volume manga created by Tsutomu Nihei as a prequel to his ten-volume work Blame!. The threshold is set above the level of the 'noise' and so when there is no 'signal' the gate is closed. A noise gate does not remove noise from the signal. When the gate is open both the signal and the noise will pass through.
More advanced forms of noise gates have more features. Most common is the ability to control how quickly the gate will close once the level has dropped below the threshold. This is known as the release, and allows for a smooth cutoff rather than an abrupt cutting of the sound when the gate closes. Likewise the ability to set the time it takes for the gate to open is available on some gates. This is known as the attack control. If the release time is too short a click can be heard when the gate re-opens. Sometimes there is also a hold control which allows you to define the amount of time the gate will stay open after the signal falls below the threshold. This is useful during short pauses between words or sentences in a speech signal. [1]
The amount of attenuation when the gate is closed can be set by the range control. In Physics, attenuation (in some context also called extinction) is the gradual loss in intensity of any kind of Flux through a medium Often there will be complete attenuation, that is no signal will pass when the gate is closed. In some circumstances complete attenuation is not desired and the range can be changed.
Advanced gates have a sidechain. Dynamic range compression, also called DRC (often seen in DVD player settings or simply compression, is a process that reduces the Dynamic range of This is an additional input that allows the gate to be triggered by another audio signal.
A variation of a sidechained noise gate used in electronic music production is a trigger gate, trancegate or just simply gate, where the noise gate is not controlled by audio signal but a preprogrammed pattern resulting in a precisely controlled chopping of a sustained sound. Electronic music is music that employs Electronic musical instruments and Electronic Music technology in its production
Noise gates often implement hysteresis, that is, they have two thresholds. A system with hysteresis can be summarised as a system that may be in any number of states independent of the inputs to the system One to open the gate and another, set a few dB below, to close the gate. The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to This means that once a signal has dropped below the close threshold, it has to rise to the open threshold for the gate to open, so that a signal that crosses over the close threshold regularly does not open the gate and cause chattering. A longer hold time as described above also helps avoid chattering.
Audio noise reduction
In audio post-processing, noise gating reduces steady noise sources such as rumble from LP records, hiss from audio tape, static from a radio or amplifier, and hum from a power system, without greatly affecting the source sound. A rumble is a form of loud White noise which is often created by a random sound wave existing between certain limitation points A gramophone Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. An audio signal such as music or speech is broken up into many frequency bands by a collection of overlapping band-pass filters, and if the signal amplitude in any one band is lower than a preset threshold then that band is eliminated from the final sound. Music is an Art form in which the medium is Sound organized in Time. Speech refers to the processes associated with the production and perception of Sounds used in Spoken language. In brief the Passband is the range of frequencies or wavelengths that can pass through a filter without being attenuated A band-pass filter is a device that passes frequencies within a certain range and rejects ( Attenuates frequencies outside that range This greatly reduces perceptible background noise because only the frequency components of the noise that are within the gated passbands survive. In brief the Passband is the range of frequencies or wavelengths that can pass through a filter without being attenuated
The technique was implemented in real-time electronics in some audiophile record players as early as the 1980s, and is now commonly used in audio production post-processing, where software to Fourier transform the audio signal can yield a very detailed spectrum of the background noise. An audiophile, from Latin audio "I hear" and Greek philos "loving" is an audio reproduction enthusiast who typically listens The phonograph, or gramophone, was the most common device for playing recorded Sound from the 1870s through the 1980s The 1980s was the decade spanning from January 1 1980 to December 31 1989. This article specifically discusses Fourier transformation of functions on the Real line; for other kinds of Fourier transformation see Fourier analysis and A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. Common digital audio editing software packages such as CoolEdit and Audacity include easy-to-use digital noise gating code: the user selects a segment of audio that contains only static, and the amplitude levels in each frequency band are used to determine the threshold levels to be applied across the signal as a whole. Digital audio uses Digital signals for Sound reproduction. This includes analog-to-digital conversion, digital-to-analog conversion, storage Adobe Audition (formerly Cool Edit Pro) is a Digital audio editor Computer program from Adobe Systems featuring both a multitrack Audacity is a Digital audio editor application Audacity is Cross-platform, using the WxWidgets software library to provide a similar Graphical
Noise gating works well when the static is steady and either narrowly confined in frequency (e. g. hum from AC power) or well below the main signal level (15 dB minimum is desirable). In cases where the signal merges with the background static (for example, the brushed drum sounds in the Sun King track on the Beatles album Abbey Road) or is weak compared to the noise (as in very faint tape recordings), the noise gating can add artifacts that are more distracting than the original static. " Sun King " is a song by The Beatles that appeared on the Abbey Road album The Beatles were a pop and rock band from Liverpool, England formed in 1960 Abbey Road is the eleventh official album released by The Beatles. In Sound and Music production, the term sonic artifact or simply artifact refers to sonic material that is usually accidental or unwanted resulting from
In the context of a multi microphone recording session, noise gating is employed to reduce the leakage of sound into a microphone from sources other than the one the microphone was intended for. One example involves the mic-ing up of a drumkit. A drum kit (also drum set or trap set) is a collection of Drums Cymbals and sometimes other Percussion instruments such as cowbells In most multi-mic drum recordings, amongst others, a microphone will be used to capture the snare drum sound and another to capture the kick drum sound. The snare drum is a Drum with strands of snares made of curled metal wire metal cable plastic cable or gut cords stretched across the a drumhead typically A bass drum is a large Drum that produces a note of low definite or indefinite pitch. The snare microphone will output a signal comprising of a high level snare signal and a lower level kick drum signal (due to the further distance of the kick drum from the snare microphone). If the threshold level of the noise gate is set correctly a snare drum signal can be isolated. To fully isolate the snare drum signal the release rate has to be quite fast which can cause the tail end of the snare sound to be 'chopped off'. This can usually be remedied by the inclusion of one or more 'overhead' microphone(s), which can act as a general 'audio glue' for all the other gated sources.
Recording usages
A good example of time-controlled noise gating is the well-known "gated reverb" effect heard on the drums on the Phil Collins hit single "In the Air Tonight", created by engineer-producer Hugh Padgham, in which the powerful reverberation added to the drums is cut off by the noise gate after a few milliseconds, rather than being allowed to decay naturally. Gated reverb is an audio processing technique that is applied to recordings of drums (or live sound reinforcement of drums in a PA system) to make the drums sound powerful and Philip David Charles Collins, LVO (born 30 January 1951 Chiswick, London) is an English Singer-songwriter, Drummer " In the Air Tonight " is a song by Phil Collins which first appeared on his 1981 album Face Value. Hugh Padgham is a British Record producer. He has won a string of awards including four Grammys with Producer of the Year and Engineer of the Year amongst them A millisecond (from Milli- and Second; abbreviation ms is one thousandth of a Second. This can also be achieved by: sending the 'dry' snare signal to the reverb (of other process) unit, inserting a noise gate on the path of the reverb signal and connecting the snare sound to the side chain of the gate unit. Dynamic range compression, also called DRC (often seen in DVD player settings or simply compression, is a process that reduces the Dynamic range of With the gate unit set to 'external sidechain' (or 'external key') the gate will respond to the snare signal level and 'cut off' when that has decayed below the threshold, not the reverberated sound.
It is a common production trick to use spurious combinations of side chain inputs to control longer, more sustained sounds. For example, a hi-hat signal can be used to control a sustained synthesized sound to produce a rhythmic melodic (or harmonic) signal which is perfectly in time with the hi-hat signal. A hi-hat, or hihat, is a type of Cymbal and stand used as a typical part of a Drum kit by percussionists in R&B, hip-hop, Disco Rhythmic contemporary, also known as rhythmic top 40, rhythmic contemporary hit radio or rhythmic crossover, is a music Radio format that A hi-hat, or hihat, is a type of Cymbal and stand used as a typical part of a Drum kit by percussionists in R&B, hip-hop, Disco A good example of this use of the device can be found on the Godley & Creme concept album Consequences. Godley & Creme were a duo of English Pop musicians and Music video directors Kevin Godley and Lol Creme. In Popular music, a concept album is an Album which is "unified by a theme which can be instrumental compositional narrative or lyrical" The album's story required the creation of a number of special sound effects that would convey the impression of natural disasters. For the album by The Jam see Sound Affects. Sound effects or audio effects are artificially created or enhanced Sounds A natural disaster is the consequence of a Natural hazard (eg For the "Fire" sequence, Godley and Creme used a noise gate, triggered by the sound of multitracked voices, that created the 'voice' of a raging bushfire. Ladysmith-RFSJPG|right|thumb| Ladysmith NSW RFS fire fighting tanker]]A Bushfire is a Fire that occurs in the bush (collective term for During the recording of this segment, each time the voice signal began, it triggered the noise gate to open up another channel, which carried a pre-recorded loop of a crackling sound (created by overdubbing the sound of Bubble Wrap being popped in front of a microphone). Bubble Wrap is a pliable transparent Plastic material commonly used for packing fragile items The combined voices and crackling created an eerie and quite convincing 'talking fire' effect.
A noise gate can sometimes (and to varying success) be used to 'tighten up' the playing of musicians. A musician is a person who plays or writes Music. Musicians can be classified by their roles in creating or performing music An instrumentalist plays a If, for example, in a recording the kick drum is quite 'in time' but the bass player is slightly ahead, controlling the bass guitar via a gate whose sidechain is fed by the kick drum signal can pull the two sounds together.
References
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