Roland EV-1-WL Connection Manual page 45

NS (NOISE SUPPRESSOR)
This effect reduces the noise and hum picked up
by acoustic instrument's pickups or a microphone.
Since it suppresses the noise in synchronization
with the envelope of the sound (the way in which
the sound decays over time), it has very little
effect on the sound of the acoustic instrument or
the microphone, and does not harm the natural
character of the sound.
Parameter
ON/OFF
Value
OFF, ON
Explanation
Turns this effect on/off.
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