Removing NOISE from an MP3 using Audacity

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Removing NOISE from an MP3 using Audacity

Postby Hugh-AR » 25 Aug 2019 22:18

Removing NOISE from an MP3 using Audacity

Scroll down towards the end to read about a problem I encountered after downloading an updated version of Audacity (Version 2.3.3) and how I solved the problem.

I was listening to some MP3s I had recorded a while back and came across this one .. Rock Around The Clock. When I listened to it I realised that there was a 'drone' sound running right through it which must have been caused by the recording equipment I was using.

Here are the first few bars of the piece .. and I have left the end of the recording in as well so you can hear the 'drone' sound again. The 'drone' does actually go right through the whole piece, but as the music is much, much louder than the 'drone' you are not really aware of it. But it is still there, and really I could do without that 'drone' sound interfering with my recording.

Click the below to listen .. and click the back-button afterwards to get back to this page.
Rock Around The Clock DEMO with 'drone' sound at the beginning and end

To emphasise the sound I am on about, here it is again .. and this time I have lengthened the 'drone' sound so you really can't miss it!

Click the below, and again click the back-button to get back to this page afterwards.
Lengthened 'drone' sound at the beginning

You can use Audacity to completely remove that 'drone' sound from the whole recording.

First, 'Open' your track in Audacity. You then have to tell Audacity what the sound is that you want removed. This can be a 'drone', as I have here, but if you were recording 'live' using microphones it could also be 'chatter' from an audience; or cars out in the street; or doors slamming etc. But you do have to get this sample from a 'quiet' section of your recording in the first instance.

In our case we'll get a sample from the start of the piece. Click and 'drag' the mouse across a suitable section of the noise you want to remove. This will now be highlighted, as in the illustration below:

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Next, click on Effect (at the top) and in the drop-down box choose Noise Reduction...

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Step 1 is to Get Noise profile .. so click on that. Audacity will get the noise profile from the bit you have highlighted, which is why you have to select the area where the noise is first.

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When you click on Get Noise Profile the box disappears. What you have to do next is to 'highlight' the section where you want that Noise Reduction to take place .. which basically in this case is the whole piece. So click Select (at the top) and choose All.

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Now go to Effect and choose Noise Reduction again. The same box will come up as before .. but this time we want Step 2.
You will see there are options to choose for the actual noise reduction, and the ones you need are the 'default' ones .. which are showing in the boxes in the image below. If these are anything different, then change these values to:

Noise reduction (dB): 32
Sensitivity: 150.00
Frequency smoothing (bands): 0

And this time, Reduce is automatically selected and the OK is available for you to click on. So click on OK .. and Audacity will remove that 'noise' from the whole piece, wherever it occurs.

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You now need to 'save' what you have done .. which is of course to click on File, Export, Export as MP3 .. and give your piece a name.

This is how my recording of Rock Around The Clock sounds now. That hum has gone. Not only from the beginning and the end, but from everywhere in between, so the recording you are listening to is a lot clearer than it was.

Click the below to listen .. and click the back-button afterwards to get back to this page.
Rock Around The Clock with the 'drone' sound removed

Hugh
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Re: Removing NOISE from an MP3 using Audacity

Postby Rev Tony Newnham » 26 Aug 2019 07:16

Hi

There are various computer programmes out there that do noise reduction. Most work in much the same way as Hugh describes above. Although the results can be good to excellent, it's better to get rid of noise sources prior to recording if you can! Noise reduction (NR) works best on noise sources that are relatively constant - I very much doubt that simple noise reduction as Hugh describes would deal with background chatter on a recording. Obviously, such noise before the piece starts, and after reverb dies away (be careful not to clip the end of any reverb!) can be edited out. One tip is, if you can, to record 30 secs or so of the ambience of the room that you can drop in what you need to keep gaps the same length if you need to take out a distracting noise. (A fairly quick cross-fade can be used to reduce and discontinuities in sound if needed)

However, be very careful when applying noise reduction, as too much can cause unwanted artifacts on the music (or speech) you want to keep - often a sort of "bubbly" sound. Listen very carefully before you commit to the settings you've chosen - you may need to compromise on the amount of noise that you remove.

I've done a lot of this sort of work over the last few years remastering recordings for the Electronic Organ Constructors' Society library. the ones I've dealt with so far have been on open reel tape, mainly on small spools at 3 3/4ips. In removing tape hiss it's all too easy to start removing the high frequency content of the wanted signal for example.

There are also programmes out there that will reduce or remove crackle & clicks (like you tend to get on vinyl records). Clicks can also be caused by operating stops - or even someone turning an electrical appliance on or off elsewhere in the house - something else to beware of.

Listen carefully before you start recording - the ear quickly gets used to noise that's there all the time and ignores it. We used to live close to a boarding kennel, and visitors would often comment on the noise the dogs made - and we'd often say "what noise?" Listen carefully in your music room - is there a clock ticking? Is there a clock that chimes the hours? And don't forget things like refrigerators and other domestic appliances, traffic noise and so on.

Every Blessing

Tony
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Re: Removing NOISE from an MP3 using Audacity

Postby Hugh-AR » 26 Aug 2019 08:43

Very true, Tony. Best to 'keep an ear out' for any obvious noises before you start recording. The same applies when taking photographs. Keep an eye open. The number of times I have seen photographs of friends at a table in a restaurant .. and in the foreground are wine glasses and a wine bottle!

The brain gets very accustomed to hearing repetitive sounds and 'switches off'' hearing them. I have told this story before, but I'll tell it again as this is exactly the sort of thing you have to be aware of.

When our children were young, I recorded 'Top of the Pops' from the television using a microphone. It was the December one where they played all the top songs for the whole year. Thought the children would like to listen to it again later. I warned them not to make a noise while they were watching, and hoped we wouldn't get a lorry passing up the street as we were quite close to the road. All went well.

Then much later they asked me if I would put the recording on for them to listen to again. Started it going, and then .. horror of horrors! There was a 'tweet tweet .. tweet tweet' running right through the recording. It was the budgerigar, which I hadn't taken out of the room when I did the recording! This is how the brain 'cuts out' what it doesn't want to listen to. At the time of the recording none of us were aware of the budgerigar 'tweeting' in the room; but when the sound came from the speakers with the music there was no way you could filter it out.

Tony .. I like your comment about ticking clocks, and even 'chiming' clocks, as this is another thing you wouldn't really notice unless you were specifically listening for it.

Hugh
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Re: Removing NOISE from an MP3 using Audacity

Postby Hugh-AR » 26 Aug 2019 22:35

Now I have come across another MP3 recording that has a 'hum' in it. No doubt caused by faulty recording equipment or leads used to make the recording. This is the recording previous Member Eddie Smart did when creating his 'multitracked' orchestral piece of Mozart's Eine Kleine Nachtmusik (first movement). It took him 8 months to get this to a standard he was happy with. There is a post all about this in Multitracking, here:

Do a right-click to open this up in a New Tab
http://www.tierce-de-picardie.co.uk/viewtopic.php?f=403&t=7168#p47587

Click the LINK below to listen to the beginning of his recording.
After you have listened, click the 'back-button' to get back to this page.
The beginning of Eddie Smart's Eine Kleine Nachtmusik recording (DEMO)

You can hear that 'drone' sound again at the beginning. So to remove that sound from the whole piece we take the same steps as before.

1. Highlight a section where the drone sound is by clicking and dragging the mouse.

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2. Click on Effect (at the top) and in the drop-down box choose Noise Reduction...

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3. In the box that comes up we need to carry out Step 1, so click on Get Noise Profile. Audacity will take the bit you have previously highlighted as the 'sample'.

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4. The box you had will have disappeared. Now you need to tell Audacity which part of the file you want it to apply the Noise Reduction to. In this case it is the whole file, as that drone sound is there from beginning to end. So click on Select and All to select the whole file.

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5. Now click on Effect and choose Noise Reduction... again. This time we need to carry out Step 2. Make sure the options showing are as below, and then click OK.

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6. The 'drone' sound will now be removed from the whole file, and while it is doing it you will see this message.

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7. All that now remains to be done is to 'save' the adjusted file. To do this click on File (at the top); choose Export; then Export as MP3. Give your MP3 a name, and allocate a destination Folder for it.

For the MP3 above, this is what the MP3 file now sounds like (no drone sound!).

Click on this LINK to listen; and afterwards click the 'back-button' to get back to this page
Mozart's Eine Kleine Nachtmusik (first movement) played by Eddie Sharp

What a great recording, and even if you're not 'into' classical music I'm sure you will appreciate what Eddie has achieved here.

Hugh
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Re: Removing NOISE from an MP3 using Audacity

Postby Hugh-AR » 24 Apr 2020 18:41

I have another track (from Ken Horton) that has a 'hum' running through it. So here's another example of using Audacity to remove that 'hum'.

Samba de Orfeu

First listen to this version of this song.



And now listen to Ken playing this song. In his recording he has a 'buzz', which although it recedes into the background once he starts playing the tune it is nevertheless still there. When listening, make a mental note of the 'buzz' at the beginning.

Click the below to listen, and then click the 'back arrow' to get back to this page after.
Ken's Samba de Orfeu with a BUZZ

So .. how to remove the BUZZ?

I have already explained how to do this in the posts above, but this time I encountered a problem! This was after I had downloaded the latest version of Audacity .. Version 2.3.3. Read on to find out what the problem was and how I overcome it.

As explained in my post above, I first highlighted a section of the noises in a 'quiet' area, as below:

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Then clicked the Effect tab at the top, and choose Noise Reduction from the drop-down box.

Chose Get Noise Profile. This tells Audacity that the 'highlighted' bit is the noise you want removed.

But in this new version of Audacity that I downloaded, this is what I got!
It says, "Value not in range 0 to 24".

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I had thought that there was a problem with my updated Audacity program, but I have discovered it is the Sensitivity that this is referring to, and this setting is in Step 2!! The Sensitivity is set at 150 (Maximum) which is far too high for this sample. So I have reduced this setting to 20, which is in the range 0 to 24. I then clicked on Get Noise Profile in Step 1 again, and this time it worked just fine. The box disappears as soon as it has sampled the 'noise'.

As I want this noise to be removed from the whole track, I now have to highlight it all. So go to the tab Select (at the top) and choose All. The whole track is now highlighted.

Next, go back to Effect and Noise reduction. This time we want Step 2. I have changed the Noise reduction (dB) from 32 to 20. Then clicked OK.

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Saved the resultant file (Export, MP3 and give the file a name) and this is how Ken's recording has ended up. No 'hum' left anywhere in the file.

Click the below to listen, and then click the 'back arrow' to get back to this page after.
Ken's Samba de Orfeu with BUZZ removed
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More on Noise Reduction using Audacity.

Postby Hugh-AR » 05 May 2023 22:20

Den has posted a topic on the Yamaha PSR 1100 keyboard .. the first keyboard he ever had.

Do a right-click to open this up in a New Tab.
http://www.tierce-de-picardie.co.uk/viewtopic.php?f=361&t=12029

Listen to this track (below) that Den recorded from this keyboard, and in particular listen to the NOISE at the beginning and at the end. In fact, the NOISE is there right through the track, but once the melody and backing start playing, the NOISE is pushed into the background. Not sure of the origin of the NOISE, but they worked with 'floppy disks' in those days!



This Topic is all about REMOVING NOISE, so here's another example of how to do it.

Run Audacity and 'Open' the MP3 track so the waveform is showing.
The first thing we have to do is is to give Audacity a 'sample' of the NOISE we want removed.
So click and drag with the mouse over the area of noise to highlight it.

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Now go to the tabs at the top, and the one we want is Effect.
In the drop-down box choose Noise Reduction...

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In the box that comes up you will see two Steps you have to take, Step 1 and Step 2 .. and you do these separately.
Check what the settings are in the bottom section.
I have set the Noise reduction (dB) to 20 as anything less than that didn't seem to remove enough of the noise.
The Sensitivity: has to be between 0 and 24.
It's a question of experimenting a bit with the numbers and seeing what you end up with. Any NOISE you remove will also remove some of the 'music', and as Rev. Tony Newnham says above, it is better to leave some of the noise rather than compromise the overall sound of the music. If you are not happy with any result you get (and this applies to anything you do in Audacity) you can click the Undo (or hold down the Ctrl key and press the letter Z), which will take you back a step to where you were before.

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First time round click on Get Noise Profile.

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Now that Audacity knows what the NOISE sounds like that box disappears.
We now have to tell Audacity what section of the track we want that noise to be removed from.
Well, the whole track.

So click on the tab Select at the top, and then All. Or, on the keypad, hold down the Ctrl and press the letter A.

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This will highlight the whole track.

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Now we have to go back to Noise reduction... in Effect ...

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... and this time, when the box appears, do Step 2. Click OK this time.

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Looking at the waveform, there is less of that noise now than what we had at the beginning.

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Below is a short DEMO for you to listen to. First, you hear a bit of Den's track 'as is' (with the NOISE); and then what it sounds like after our efforts to remove the NOISE.



And here below is the whole track so you can compare this 'adjusted' version with the original.



What do you reckon? Have we taken the NOISE REDUCTION too far and somehow compromised the music?

Hugh
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