Noise Gate

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Noise Gate

Permanent link to this post Posted by kozikowski » Fri Apr 30, 2010 2:29 pm

Has Steve's Noise Gate in any of its forms been added to the rolling list of available effects?

Koz

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Current download is available on the Audacity wiki: http://wiki.audacityteam.org/wiki/Nyqui ... Noise_Gate
Last edited by Gale Andrews on Sat Jun 25, 2011 2:33 am, edited 5 times in total.
Reason: Add wiki link
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Re: Noise Gate

Permanent link to this post Posted by Gale Andrews » Sun May 09, 2010 4:44 pm

kozikowski wrote:Has Steve's Noise Gate in any of its forms been added to the rolling list of available effects?


No - I don't even know about it. If Steve think's it's ready, first step is to post a link to it in this thread, and then post a link to this thread in audacity-nyquist mailing list.



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Re: Noise Gate

Permanent link to this post Posted by steve » Sun May 09, 2010 9:04 pm

I'm happy with the effect but have now made a minor update.
Here's a new version (version 2.2)

Changes since version 2.1
Help file updated to fit 800 x 600 screen.
Help File also included as text file in ZIP package.
Minor changes to GUI.

Features in Noise Gate 2.2
  • Gated audio can be reduced in the range 0 to -96 dB.
  • Attack/Decay variable from 10 to 1000ms.
  • Stereo tracks may be processed individually or as linked stereo.
  • Includes utility to show peak level of audio, ignoring DC Off-set.
  • Optional frequency limited gating (for hiss removal).
  • Includes optional HP filter.
  • Includes Help file.

Please post feedback/bug reports here.

Obsolete version:
noisegate_v2-2.ny.zip
This is an obsolete version - please use the latest version (below)
(4.13 KiB) Downloaded 2214 times

The latest version is available on the Audacity wiki: http://wiki.audacityteam.org/wiki/Nyqui ... Noise_Gate
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Re: Noise Gate

Permanent link to this post Posted by steve » Sat May 22, 2010 10:03 am

[Moderator note: Topic merged]
"Noise gates" are blunt instruments for bashing low level noise between tracks or audio clips.

In its simplest form it will allow sound to pass if the sound level is above a set "threshold" level, but when the level drops below the threshold the "gate" will "shut" and the audio will be muted.

NoiseGate version 2.2 has been tested with Audacity 1.3 only. Feedback from anyone that would like to try it out is welcome.

In this version there are 4 user adjustable parameters:
Gate frequencies above: > If the Gate frequency is set to 20Hz, the full signal will be processed, otherwise only frequencies above the Gate frequency will be gated. This may be useful for reducing hiss between audio clips.
Level Reduction: > This is the amount of reduction (attenuation) that will be applied to the sound when the gate is "closed".
Gate threshold: > When the audio goes below this level the gate will close. Above this level the gate will open.
Attack/Decay: > This is the length of time that will be taken for the level fall to the attenuated level and to rise back to normal.

This noise gate uses "lookahead", so when the gate is closed, it will start to open just before a sound that has a level above the threshold is encountered. This prevents the attack of percussive sounds from being lost as the gate will be fully open in time for the sound to pass through.

For anyone using Effect category grouping, the noise gate should appear in the "Dynamic Processor" section of the Effects menu.
Last edited by steve on Sat Jun 11, 2011 1:12 pm, edited 1 time in total.
Reason: link to obsolete version removed
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Re: Noise Gate

Permanent link to this post Posted by atsdroid » Wed Jul 07, 2010 11:14 am

This is "almost" exactly what I need, but I need a version modified to clamp to perfect silence, instead of just really really quiet, so that the "Detach at Silences" (a/k/a Disjoin in older versions) function will cause the quiet regions to go away.

I tried manually editing the .ny file to set the level-red variable to zero, and the result was almost perfect. When the gate closed, I got perfect silence, suitable for "Detach at Silences", but the gate opening attack then included clicks at the beginning and end of the attack window (i.e. for a 250ms attack/decay setting, two clicks, 250ms apart). The clicks proved too annoying to tolerate.

Previously, I tried the included "Gate" effect, which was a little different. This one does produce "detachable" silence, but will hold open for at least a second past the end of the desired audio, and no combination of the attack/hold/decay sliders can make the gate close any faster. I'd like to have a gate that can than open and close quickly, produce high quality output, like "Noise Gate" does, but have the option to clamp to "detachable" silence, not just _really_ quiet.

This will allow me to use the "Detach at Silences" function to quickly drop out the quiet portions below the threshold, and then I'll be slide the remaining sounds around on the timeline with minimum fuss. Which is what I really need to do for my project.

Does anyone (the author himself?) know how the "Noise Gate" plugin might be modified to accomplish this?
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Re: Noise Gate

Permanent link to this post Posted by steve » Wed Jul 07, 2010 10:30 pm

atsdroid wrote:Does anyone (the author himself?) know how the "Noise Gate" plugin might be modified to accomplish this?


I think if you change line 166 to this should do it:
Code: Select all
      (mult s-in (sum (mult -1 level-red)(clip (gate gatefollow lookahead risetime falltime  floor threshold) 1.0)))))
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Re: Noise Gate

Permanent link to this post Posted by atsdroid » Thu Jul 08, 2010 4:26 am

That was perfect! I'm so happy!

I modified the code as you instructed, appending a note to the name to differentiate it from your original plugin, and tried it out. It perfectly clamped the regions below the threshold to perfect silence, allowing me to use the disjoin command to separate out the individual audio pieces for sliding about the timeline. This will speed my editing up greatly!

Thanks so much, stevethefiddle! Not being a LISP/Nyquist programmer, the obviousness of your simple code change was only apparent _after_ the fact. I appreciate your effort!

This next bit is off-topic, but demonstrates a use case for Audacity. In case any reader my be curious what I'm up to, I'm using this with audio streams from the LiveATC.net archives. If you're an aviation enthusiast, you might already know the site, which fosters a community of folks who capture and stream air-band communications from nearby airports. Students can find the site invaluable for learning how ATC controls traffic, and developing an "ear" for comprehending the often rapid fire instructions.

To follow the action where multiple control positions might be available for listening, it's helpful to jump from channel to channel to hear how ATC commands manage the flow of individual aircraft. Often, communications overlap in time, so this modified filter allows me to build a timeline of several recorded ATC channels, and slide any overlapping individual transmissions to areas of silence in the other channels, while keeping relatively close to the original timeline. The project can then be mixed down into a single audio file, and you can then listen and build up a mental picture of the traffic being managed, and how ATC is guiding flights to maximize airport flow. This can be a helpful learning aid for student pilots who will eventually need add their voices to this din and understand and be understood by their fellow airmen.

Cheers.
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Re: Noise Gate

Permanent link to this post Posted by waxcylinder » Thu Jul 08, 2010 8:38 am

atsdroid wrote: In case any reader my be curious what I'm up to ...

Very interesting atsdroid, It's always fascinating to see the many non-obvious and varied uses that Audacity can be put to.

Thanks for that post.

WC
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Re: Noise Gate

Permanent link to this post Posted by steve » Thu Jul 08, 2010 4:10 pm

atsdroid wrote:That was perfect!

It was a bit of a hack really, but since you brought this up, I can think of a couple of other cases where gating to silence would be useful, so I'm updating the Noise Gate to add that as a feature.
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Re: Noise Gate

Permanent link to this post Posted by kozikowski » Fri Jul 23, 2010 10:38 pm

So that's what? 2.3?

Koz
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