Hit the Preview button and listen to the effect. The Noise Removal process has a stronger effect when the Noise Removal slider is further to the right. That means 24 dB for Noise Reduction, 500 Hz for Frequency Smoothing and 0.50 seconds for attack/delay time. If not, just put the sliders in the middle of their ranges. If you've done a recording in similar circumstances before, then you might as well start with the same settings that worked well last time. again, and set the sliders to their first position. We're only going to use it to Preview the settings, so it doesn't have to include the whole file. It doesn't need to be very long, say about ten seconds. We'll use this to experiment with to find the right settings for the sliders. Next, I like to select a section of the file that has some silence and some voice. That tells Audacity what the noise looks like. and then hit the Get Noise Profile button. No clicks, no breathing, no page turning, nothing except room tone. Make sure that the room tone is the only sound in the recording. You don't need a huge amount, but it's helpful to have a few seconds. How much reduction? OR Using the noise removal dialogДЇirst select a section of the example noise. As we Librivoxateers ought to be adding 5 or 10 seconds of silence at the end of our recording, that is a perfect opportunity to gather some room tone. It's also useful to have as a source to replace other unwanted signals, instead of zeroing the recording, which sounds unreal. That is commonly called room tone, or room noise. This means that it is vital to capture some noise without any other signal. We have sliders to tell Audacity how lenient or severe it should be when it is deciding whether some part of the recording looks like the example. Audacity can only remove the part of the signal that looks like the example. The noise that we show to Audacity is an example, not a definition. It would be nice to get rid of all of the noise component, but unfortunately it's not so easy to precisely identify the noise component. Then it reduces the contribution from the noise component. To get Audacity to remove noise, you must first show it what your noise sounds like, and then Audacity separates your recording into noise and non-noise components. So now that we know that recording some noise is inevitable, especially in the non-profession situations in which most of us record, how do we get rid of what we have but don't want?

use a condenser microphone, rather than a dynamic, or electret.

get closer to the microphone, but not so close that the air current from your mouth directly hits the microphone.

avoid tiled rooms, or other large expanses of hard surfaces, which tend to be echo-y.

use battery-powered equipment (tends to eliminate mains hum, too).

This is why you want to record in as quiet an environment as possible. It sounds about as loud as background noise in an office. That amount of amplification will raise the level of the noise to -30dB (-30 = -70 + 40) which is much more audible and intrusive. If the loudest part of your signal is much quieter, say -40dB, then you will need a lot more amplification to get a decent output level, namely 40dB.

That will raise the noise levels to -60dB, which is all but inaudible. The less you have to amplify, the smaller the noise component of your recording will be.ДЇor example, if the loudest part of your signal is at -10dB and the noise is at -70dB, then you will want to amplify by 10 dB to get your signal to 0dB (which is standard).

Make the signal as large as possible, relative to the noise, without going so far that you get clipping. That means that our key strategy for removing noise from recordings is:

Any noise captured before any amplification is also amplified along with the signal. Signals from microphones are very small, much smaller than the signals that are output by a music player, so every digital recording system will have at least the following components:Д®very stage except the last will add some noise. What is noise? Noise is nothing more than unwanted sound in your recording.

2.1 How much reduction? OR Using the noise removal dialog.

How to reduce clipping in audacity