[linux-audio-user] Noise gate

Sampo Savolainen v2 at iki.fi
Sat Feb 12 07:19:33 EST 2005

On Sat, 2005-02-12 at 02:32 -0500, John Check wrote:
> On Wednesday 09 February 2005 12:50 pm, timg at expressmart.com wrote:
> > I still hae a bit of noise in my out puts.. and ALOT of noise on my tracks
> > ;) is there a noise gate?
> > I trues to use the ladspa labelled "gate" and either could not figure it
> > out or it did not do what I exprected it to do...
> > thanks ;)
> Noise gates will shut off ambient noise (i.e. bleed) effectively between 
> passages provided there is sufficient dynamic range between the noise and the 
> signal you want . Won't do anything for noisy output.

For some reason the SWH gate (from gate_1410.so) has strange default
settings in Ardour. You may have ran into the same problem I had.

The gate has controls for the LF key filter and HF key filter. LF key
filter means "filter out frequencies below the value", HF means "filter
out frequencies above the value". Both filters only affect the "key"
signal which is the signal that controls the gate. They do not affect
the signal passing through the gate when the gate is open.

In jack-rack the default values are:
 LF key filter (Hz): 33.599998
 HF key filter (Hz): 23520.000

But in ardour, the default values are:
 LF key filter (Hz): 0.001
 HF key filter (Hz): 0.490

Which means that the bandwidth for the key signal is VERY narrow. The
key signal is practically zero. 

I actually first thought that the gate didn't work, because I thought
"LF key filter" meant a lowpass filter and HF a highpass.

I hope this clears things up for you.

Sampo Savolainen <v2 at iki.fi>

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