How can I eliminate sounds below a certain threshold?

Question

Using Audacity, I can highlight a section of an audio file, select Effects > Noise Reduction > Get Noise Profile, then Select All, and then again Effects > Noise Reduction, and this time "OK" to greatly reduce the volume of the sound captured via that first Effects > Noise Reduction > Get Noise Profile.

However, I have to do this several times throughout a recording for various sounds which I want to lower in volume. Specifically, these are "inhalations" that are recorded when I am reading.

Is there a way to eliminate all sounds below a certain volume threshold, so that the sound of breathing is always completely eliminated, as well as all other faint sounds?

IOW, make it so that only the "speech" is recorded, and none of the "ancillary" sounds?

I would especially like to be able to add this to a chain, so that the entire recording is "scanned" and low-volume sounds converted to silence. Specifically, I would like to add it to this chain:

UPDATE

I downloaded the Noise Gate, but don't know where to go from there to install it into the Effects menu. After Effect > Nyquist Prompt... > Load, and then selecting the Noisegate.ny file, I see no "Noise Gate" on the Effects menu.

I can subsequently (after recording some sound or noise) select Effect > Nyquist Prompt... and see this, though:

If I select the "OK" button, I see this:

...but when I select "OK" there, no change is made to the recording, but I get a dialog, "Nyquist returned the value 250.000000"

Answer 1

I doubt you will get an acceptable result with a simple gate setup: while you may get rid of low volume breathing sounds, it will also chop away natural endings.

Noise reduction plugins with noise profile capture functionality tend to distort the audible material too - making it sound cheap and wobbly.

I can strongly recommend the DeBreath plugin by Waves:

It works very well!

I am not affiliated with Waves in any way, and I'd like to give you other alternatives if I just knew about them.

You may be able to achieve something similar with a sidechained gate/expander, where the key signal is high passed to expose as much unique breath sound as possible, but you wil most likely run into the same issues as mentioned above (just to a lesser extent).

Update 2022: Alternative options may be iZotope RX or Waves Clarity VX / VX Pro, in particular if the unwanted noise is background noises like traffic, motors or fans. Waves Clarity is the newest and it delivers a very impressive result:

Answer 2

It really depends on the material; are these sounds that you want to remove truly peaking at a lower level than every bit of the speech? How about in loudness or 'energy'?

You need to look into the kind of sounds you want to remove and see how they differ from the ones you want to keep. This is key to being able to separate them.

Are they of a shorter duration than the sounds you want to keep? Are they at a different frequency? Do they have some sort of regular pattern?

I'm just trying to get you to think in the right way. You need to first define a difference before you can look for a tool to remove them.

You have established that the unwanted sounds are at a lower amplitude than the sounds you want to keep. This makes things very easy; all you have to do is find a tool that will allow a signal to pass through(or open the gate) if the amplitude passes a certain threshold, and reject any signals that fall short of this threshold(close the gate). It's almost as simple as that.

I say almost, because there are other parameters to consider. How fast do we want the gate to open and close? because we don't want any sharp clicks and we may want a smooth transition through the attack and decay of this opening and closing gate. Also, do we want the closed gate to completely attenuate the signal, infinitely, or do we want to just gently attenuate the signal by, say 12 dB? Do we want the left and right channels to be 'gated' individually, or do we want to treat them as one signal? These are the basic extras that a generic gate provides.

If you are having trouble with Audacity's Nyquist gate then I would suggest you look for a free VST gate online. There are many to choose from, pretty reputable companies release free VSTs if they are simple enough, like noise gates.

best free noise gate vstau plugins from bedroomproducersblog.com
unfiltered audio g8 cm free vst au noise-gate plugin from musicradar.com
Other cool free VST FX(Voxengo)
Immense list - free Gates/DeEssers

I think your main problem is understanding how to use these gates or de-essers(de-essers are just gates that target high frequency sounds like "sssss" sounds (or "sibilant frequencies"))

I explained the basic parameters of a gate, but there is one more that could be helpful to you, it is an internal sidechain feature, sometimes called other things but basically, it allows you, like the de-esser, to target certain frequencies with the gate. It usually consists of two parameters, an upper and a lower cutoff frequency. So if you set the lower cutoff to 2 kHz and the upper to 5 kHz, then the gate will only be triggered if the amplitude of this range(2-5 kHz) passes the threshold. So these inhalation sounds could effectively be targeted in this way.

So a word on setting up a basic gate;
To initially set up a gate, you want to set the attack/decay to a low level; zero if you like, set the attenuation(level reduction) as low as possible, then sweep the threshold down, starting at 0 dB. This will give you a good idea of when the gate triggers, so you can then set the threshold to the appropriate level(just above the unwanted noise), then adjust the other settings to fine tune.

Good luck!

Answer 3

Yes sortof maybe.
Special plug ins can help a lot depending on the exact problem.

The only correct thing to do is to get a better recording. Teach the speaker/vocalist how to use the mike to avoid breath sounds.

Use a quiet room to avoid ancillary sounds.

Noise reduction works quite well to remove hissy type noise but other sounds, NOT properly called noise in this context, need other methods to help eliminate them.

And yes you can remove all sound below a level with a gate. You might not improve the speech that remains though as much as you think it will.