PreSonus AudioBox™ iTwo Owner's Manual

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Threshold. The gate threshold sets the level at which the gate opens. Essentially, 

all signals above the threshold setting are passed through unaffected, whereas 

signals below the threshold setting are reduced in level by the amount set 

by the range control. If the threshold is set fully counterclockwise, the gate is 

turned off (always open), allowing all signals to pass through unaffected.
Attack. The gate attack time sets the rate at which the gate opens. A fast attack 

rate is crucial for percussive instruments, whereas signals such as vocals and 

bass guitar require a slower attack. Too fast of an attack can, on these slow-

rising signals, cause an artifact in the signal, which is heard as a click. All gates 

have the ability to click when opening but a properly set gate will never click. 
Hold. Hold time is used to keep the gate open for a fixed period after 

the signal drops below the gate threshold. This can be very useful for 

effects such as gated snare, where the gate remains open after the 

snare hit for the duration of the hold time, then abruptly closes.
Release. The gate-release time determines the rate at which the gate 

closes. Release times should typically be set so that the natural decay of the 

instrument or vocal being gated is not affected. Shorter release times help 

to clean up the noise in a signal but may cause “chattering” in percussive 

instruments. Longer release times usually eliminate “chattering” and should 

be set by listening carefully for the most natural release of the signal.
Range. The gate range is the amount of gain reduction that the 

gate produces. Therefore, if the range is set at 0 dB, there will be no 

change in the signal as it crosses the threshold. If the range is set 

to -60 dB, the signal will be gated (reduced) by 60 dB, etc.
Key Listen. The key listen allows the user to listen to 

the signal that is being filtered by the gate. 
Frequency Key Filter. Some gates offer a variable frequency control allowing the 

user to set a specific frequency band that the will cause the gate to open or close. 
Noise Gating. Noise gating is the process of removing unwanted sounds 

from a signal by attenuating all signals below a set threshold. As described, 

the gate works independently of the audio signal after being “triggered” by 

the signal crossing the gate threshold. The gate will remain open as long as 

the signal is above the threshold. How fast the gate opens to let the “good” 

signal through is determined by the attack time. How long the gate stays open 

after the signal has gone below the threshold is determined by the hold time. 

How fast the gate closes is determined by the release. How much the gate 

attenuates the unwanted signal while closed is determined by the range.
Noise gates were originally designed to help eliminate extraneous noise and 

unwanted artifacts from a recording, such as hiss, rumble, or transients from other 

instruments in the room. Since hiss and noise are not as loud as the instrument being 

recorded, a properly set gate will only allow the intended sound to pass through; 

the volume of everything else is lowered. Not only will this strip away unwanted 

artifacts like hiss, it will add definition and clarity to the desired sound. This is a very 

popular application for noise gates, especially with percussion instruments, as it 

will add punch or “tighten” the percussive sound and make it more pronounced.