Noise Reduction

Hi all; Lloyd Here, using 2.1.3 on a fairly new Windows 10, HP Laptop: The following three questions all apply to the use of Effects>Noise Reduction NR; in use for production of a half-hour radio broadcasting program during which I read text only, simple, but always oddities. In this case, all is going well but the air conditioning overhead outlet creates a low-level hum that I’d like to get rid of. It is automatic which means that the AC turns on and off every ten or fifteen minutes.

Question 1: When is it best to apply the NR “Sample” as stated in the manual? At the beginning of a long single-voice recording? OR… After the completion of a half-hour recording and preliminary SAVE command has been used?

Question 2: Step 2 in the Manual implies that I should apply NR after my 30-min program is complete and then highlight (select) the entire program as the “SAMPLE” for the NR process. This doesn’t sound right. I’m thinking that the sample ought to be defined before starting anything. When should th NR process be set up and initiated?

Question 3: In setting up the NR process, roughly how large should the SAMPLE be (2 sec, 10 sec, 1 min, more???

Question 4: If NR is activated and recording is in process, what happens if the noise itself is removed? I.e., when the air conditioning fan turns off in the middle of a sentence or paragraph?

Thanks in advance to whoever takes the trouble to answer these questions.

Best to all.


Post a sample of your voice at normal level with the noise in the background.

Do it roughly to this format. Do Not Process anything and yes, it needs to be in WAV format.

Post the address of the instructions that said to use the whole performance as Profile. There are some highly specialized techniques that can sometimes use that, but, no that’s not normal as far as I know.


the AC turns on and off every ten or fifteen minutes.

Any chance of recording in a room without that problem? We can try to solve it all in post production tricks, but I don’t think it’s ever going to sound completely transparent.

Depending on the sound, we may be able to use specialized hum remover or notch filters.

We will see.

My sister has and I had in my old house, a switch that forced the air handlers on all the time and just the pump switched on and off periodically. You can use that when you’re taking a shower and the air conditioner will suck all the moisture out of the air.

That may actually be easier to deal with than an air handler cycling.

If you have the compressors on the roof which is common in Los Angeles, I wouldn’t be surprised if it shook the whole house. That brings us up to: can you record somewhere else?



I am being led astray; I think we would be better off if you turned this over to another team member. According to the manual, this should not be a difficult issue. Further, I don’t need any comments about changing to another studio or having my voice analyzed. Nor do I need any analysis about compressors on the roof — or changing studios. I have what I have, it’s going to stay that way, and I don’t intend to rip out the a/c unit or the ductwork to get over this hump.
I simply want the questions answered. Finally, you ask that I post a sample by clicking onto some non-existent link at the bottom of my screen — I can find no such thing. Oddly, you actually inadvertently answered one of my questions (Question #3) without knowing it and without attempting to follow my other questions. Finally, I don’t want any tricks or work-arounds. The manual says this function is there and all I need are the parameters to make it work.

So please discontinue this inquiry. I’ll post it again with a few different words and please pass it on to another tech for processing.



Perhaps I can have a go. I’ll not even look at what Koz has written before I post, so this will be an independent second opinion.

That’s pretty old. It is highly recommended that you update to the current version (2.2.2) at your earliest convenience. You can get it here:

Air conditioning noise can be tough to remove. Remove low level constant hum or hiss are relatively easy so long as they are (1) low level compared with the audio, (2) constant, not intermittent, not pulsing, not varying in tone or pitch or volume. Air conditioner noise typically does not match that description.

The correct and widely recognised “best solution” to noise problems is to avoid them. Prevention really is much better than cure, and this is why recording studios will never go out of fashion. Unfortunately, this is not always possible for people producing audio at home, so we then have to look to “rescue” from a less than ideal situation.

This is open to personal preference. It is definitely worth making short test recordings before engaging in a long recording. If it turns out that the recording equipment / environment / recording setting, simply don’t provide good enough sound quality, then best to know that before spending hours. I generally prefer to do my recording first (after test recording) and then process later.

The noise reduction effect is highly dependent on how well the noise sample matches the noise that you are trying to remove. If the noise changes, then you need a new noise profile. A “brurururururu” noise sample will not work with a “brererererere” noise.

You need to listen carefully to the noise throughout the recording. Does it sound exactly the same at the end as it does at the start? If not, you will need to split the recording into sections each time the noise changes. If the tone or level of the noise is different as the air conditioning starts up, then that will probably give you an unusable bit each time it starts up.

Assuming that you have a half hour recording and the noise is constant throughout, then select a couple of seconds from anywhere that the recording is only noise, and make the noise profile from that, and then apply to the whole of the 30 minutes. If the noise in the first 10 minutes is different from the last 20 minutes, then split the recording into two sections, get a noise profile for the first section and apply to the first section, then get a profile for the second section and apply to the second section.

A couple of seconds is fine. Very short (less than a couple of seconds) may not work as well, but longer than a couple of seconds will probably not give noticeably better results.

The Audacity Noise Reduction effect does not work like that. It is not a “real-time” effect. All Audacity effects work with audio that has already been recorded, not on audio as it is playing/recording. If your sound card has a “real-time” noise reduction setting, then usually it is best to turn that off because such effects are generally not good enough for recording (though may be useful for making internet voice calls).

To be able to offer advice about how effective noise reduction is likely to be, we would need an audio sample, in WAV format, containing some “noise only” and some “normal voice”.

According to the manual, this should not be a difficult issue.

Running the Noise Reduction effect is easy… However, it’s not always easy to get good results. As I always say… Noise reduction works best when you have a constant very-low level background noise… It works best when you don’t really need it. If the noise is bad, the cure can be worse than the disease.

Maybe you can fix it in post-production, maybe not. It’s worth a try…

Pros still record in soundproof studios with good low-noise equipment, etc. TV & radio studios are soundproof. On-location movie dialog is re-recorded in the studio, etc. (With on-location news, they try to minimize the noise and then they just live-with what they get.)

Distortion and frequency response have pretty much been “solved” but noise is still a problem and it’s the biggest “remaining” issue for the pros. (Well… Getting a good performance is a big issue too…)

Noise is particularly difficult with spoken word (or with a solo vocal or acoustic instrument) because there are quiet & silent parts… If you’re recording a rock band the sound is more “dense” and the noise is masked (drowned out).

…and I don’t intend to rip out the a/c unit or the ductwork to get over this hump.

Of course most of us are hobbyists and we wouldn’t do that either. But, I would turn-off the heating/air conditioning for a few minutes while I record… And/or find a different time of day to record, etc. Most “studio time” is spent editing and you don’t need a perfectly quiet environment for that (although it’s nice to have a quiet studio for that too).

Of course, more-serious hobbyists often do make architectural or structural modifications to make their “studio” more studio-like. And if you’re creating a program for radio broadcast, it should be done in a studio or in a room that can honestly double as a studio.

Hi all:

I’m now on Version 2.2.2, HP OfficeJet, Windows 10, attempting to quell air conditioning background noise (NR).

I’ve solved the NR workings on my own. It turns out that if you click on Effects > Noise Reduction, and cast your fate to the winds, just disregard all the settings that are incomprehensible, and do the following, it seems to work JUST FINE without all the quagmire of trials and WAV submittals that have been recommended. Here are the extremely complex steps to get NR to work on continuous a/c fan noise:

1)) Record your document (MS Word is the only doc I’ve tried it on);
2) Click on EFFECTS
3) Click on Noise Reduction
4) Do exactly what it says — Step 1: Select a sample of the noise you want t get rid of — in my case I chose about 5 seconds of dead air with air conditioning prominent in the background and on the WaveForm)
4) Completely disregard the other settings; that is, completely disregard step 2)
5) Choose “Reduce” (already highlighted)
6) Choose PREVIEW or OK and let it fly
7) Seems to work like a charm (although I haven’t tried any other settings or any other documents).
8) Keep your fingers crossed, don’t cross the paths of any black cats and don’t walk under any ladders for at least a week. Should be fine.
9) If any of you have some words of wisdom on any of the settings in Step 2 which might be useful (or even what they mean — Yes, I do know what db means)) please let me know.

Best to all.

The caution is not getting Noise Reduction to work at all. It can be made to work very well…on steady noises. The trouble comes when you have a moving noise.

I’m guessing Noise Reduction won’t remove the Start and Stop of the noise. Those are the two points where the actual sound of the air handler may not match the Profile.

This is where it’s handy to be able to turn the air handler on all the time and just let the chiller pump cycle on and off. Many air condition systems have a user switch for this. Mine said “FAN ON.”

If you do that, I think Noise Reduction can reduce the noise beyond audibility.


I don’t think you have that process quite down.

Drag-select your sample noise.
Effect > Noise Reduction > Profile
----the noise reduction panel will vanish after it “sniffs” the noise.

Select the show (click just right of the up arrow on the left)
Effect > Noise Reduction > Type the reduction values > OK (or Preview).

That’s it. If you have a long show you can see it ripping down the track changing the blue waves.

If you have gentle background noise you might try Noise Reduction of the Beast: 6, 6, 6. If that’s not enough, you can try 9, 6, 6.

Neither of those will affect a natural speaking voice.

There is a further thing you can do. If the noise settles around certain musical tones, you can use Effect > Notch Filter or if you’re really lucky and it settles around power line musical tones, there is a power hum filter (that I need to find).


This is the De-Hum filter.

None of these tools are perfect and taken to extremes are audible in the show. The only sure way to not have noises is not record them in the first place.