Noise Gate

Consulting the web, it seems to me that there is confusion regarding this; for example, I read that a noise (noise=rumore Gate=cancello) gate serves to eliminate noise, which in audio refers to the hiss that is usually in the very high frequencies, and that a gate mutes a signal below a certain threshold.

Then they also say that the standard operation of a noise gate involves the total suppression of sound below a certain threshold, and the total passage of it above the threshold.... I really don't understand this thing.... there is also those who compare it to a compressor and some who say it is only used on guitar, especially if the pedal (or pedalboard) generates noise... then there are those who put it on tom-toms to eliminate the decay effect... I am a little confused

There are several types of noise. Normally, the noise we are talking about is "white" noise, which affects all frequencies. The fact that you only hear it in the high frequencies is a matter of perception. In a treated room with a good system equipped with a subwoofer, you would realize that this type of noise actually affects all frequencies of the audible spectrum and beyond.

There are several ways to eliminate this type of noise, but the use of these solutions depends on the context. One must understand whether it is necessary to eliminate the noise at runtime or if it can be done in post-production. Generally, everything done in post-production is of higher quality compared to live because in post-production we do not have to account for signal processing latencies and we can afford to take all the processing time we need; in the case of noise elimination, we can opt for spectral filtering, which takes a lot of time to process the signal but promises incredible results (in this case, one even speaks of "audio signal restoration," as it is a very high-performance operation). When we are in a live setting, signal processing must occur in real-time, and therefore we must settle for some less efficient systems such as a noise gate (which has nothing to do with a compressor... I don't know where you read that nonsense. If we really want to find two analogies between analog and/or digital outboard gear, we can say that a compressor pushed to very high ratios begins to behave like a limiter, at most—excuse the pun).

Anyway, the noise gate cancels all the signal when it falls below a certain threshold. How does it work? Noise is normally at a lower volume than the instrument occupying the track, so one tries to set the threshold slightly above the noise level so as to cancel it when the level falls below the chosen threshold. Careful!! With a noise gate, the noise continues to exist when the signal is above the threshold. For example, if we are recording a guitar and set the threshold to -20 dBFs, all signal below -20 dBFs will be canceled, while the signal above it will pass through undisturbed; specifically, you will hear the guitar and the noise during the parts where the guitar is playing, and the signal will be cut, returning silence, when the guitar is not playing. The fact that the noise continues to exist when the guitar is playing is due to the fact that it is impossible to separate the noise from the signal, and the noise gate cuts or lets the signal pass depending on the set minimum threshold. Certainly, due to masking phenomena, it is very difficult to hear noise when the level of the signal we are interested in is much higher. It is a different matter to hear only the noise when the guitar is not playing, and that is why the noise gate cuts. In what way does it cut? It is possible to choose the knee with which the filter begins and stops operating, the attack time, and the release time. These parameters allow us to soften the noise cut to make the effect on the ear as smooth as possible. Imagine a noise that disappears slowly compared to one that disappears suddenly, as if you had turned off the speaker switch.

As you well say, the noise gate is used mainly on electric guitars, especially if connected to a distortion pedal, on drums, but also on many other instruments... In general, wherever its use becomes necessary.

TheSimon wrote:

There are several types of noise. Normally, the noise we are talking about is "white" noise, which affects all frequencies. The fact that you only hear it in the highs is a matter of listening. In a treated room with a good system equipped with a subwoofer, you would realize that this type of noise actually affects all frequencies of the audible spectrum and beyond.

There are several ways to eliminate this type of noise, but the use of these solutions depends on the context. One must understand whether it is necessary to eliminate the noise at runtime or if it can be done in post-production. Generally, everything done in post-production is of higher quality compared to live because in post-production we do not have to account for signal processing latencies and we can afford to take all the processing time we need; in the case of noise elimination, we can opt for spectral filtering, which takes a lot of time to process the signal but promises incredible results (in this case, one even speaks of "audio signal restoration" as it is a very high-performance operation). When we are in a live setting, signal processing must occur in real-time, and therefore we will have to settle for some less efficient systems such as a noise gate (which has nothing to do with a compressor... I don't know where you read that nonsense. If we really want to find two analogies between analog and/or digital outboard gear, we can say that a compressor pushed to very high ratios begins to behave like a limiter, at most, excuse the pun).

Anyway, the noise gate cancels all the signal when it falls below a certain threshold. How does it work? Noise is normally at a lower volume than that of the instrument occupying the track, so one tries to set the threshold slightly above the noise level so as to cancel it when the level falls below the chosen threshold. Careful!! With a noise gate, the noise continues to exist when the signal is above the threshold. For example, if we are recording a guitar and set the threshold to -20 dBFs, all the signal below -20 dBFs will be canceled, while the signal above it will pass through undisturbed; specifically, you will hear the guitar and the noise in the parts where the guitar is playing, and the signal will be canceled, returning silence, when the guitar is not playing. The fact that the noise continues to exist when the guitar is playing is due to the fact that it is impossible to separate the noise from the signal, and the noise gate cuts or lets the signal pass depending on the set minimum threshold. Certainly, due to masking phenomena, it is very difficult to hear noise when the level of the signal we are interested in is much higher. It is a different matter to hear only the noise when the guitar is not playing, and that is why the noise gate cuts. In what way does it cut? It is possible to choose the knee with which the filter begins and stops operating, the attack time, and the release time. These parameters allow us to soften the noise cut to make the effect on the ear as smooth as possible. Imagine a noise that disappears slowly compared to one that disappears suddenly, as if you had turned off the speaker switch.

As you well say, the noise gate is used mainly on electric guitars, especially if connected to a distortion pedal, on drums, but also on many other instruments... In general, wherever its use becomes necessary.

thanks a lot, it's all very understandable and clear!! now I will do some tests on logic x

You're welcome, don't mention it...

Well done, the best thing after theory is experimentation. Have fun.