Noise reduction help

Hi everyone. This is my first post on this forum, although I’ve been lurking for a while. Can I just start by saying a huge thank you to everyone on this forum for all the amazing advice you post here. I was completely lost before I discovered this place.

I need some help now with noise reduction. I’ve attached three files - the first is the raw audio, which has a noise floor of -74db, but is, as you can hear, way too quiet. The second is the same audio with the mastering macro applied. This takes the noise floor up to -69db, which does pass ACX’s requirements but I can hear a buzzing in the background, which is offputting. The third file is the mastered version with noise reduction of -5db applied, using two seconds of room tone as the noise profile. This takes the noise floor back to -75db and, to my untrained ears, sounds much better. But I know ACX frowns on using noise reduction and the last thing I want is for my files to get rejected as being overprocessed. Can someone more knowledgeable than me have a listen and tell me if the noise reduction is okay, or if there is anything else I can do to get rid of the buzzing?

I’m using a Rode NT1-A mic with U22-XT interface. I’m recording in the cupboard under the stairs, which I’ve converted into a booth with acoustic foam and heavy blankets.

Thank you.

A little bit of noise reduction is OK, so long as you can’t here that noise reduction has been applied. If you can hear a metallic bubbly quacking sound after noise reduction, then that is not acceptable. I usually use “6, 6, 3” settings.

I notice that there is a very low frequency hum at 82 Hz. I don’t know where that’s coming from, but it appears to be rock steady at 82 Hz, so can be removed using the Notch filter set to 82 Hz, Q=8. Normally I would do that before using Noise Reduction, but as the noise level is already very low it doesn’t make much difference in this case whether it is done before or after.

ACX’s “Overprocessing” rejection is usually reserved for people who are trying to convert complete trash into an audiobook by applying a laundry list of corrections, filters, effects, and processes. Those will sound dreadful no matter what you do.

ACX’s noise limit is -60dB and we strongly recommend you be able to hit -65dB reliably and with no extraordinary effort. Your noise came in at -69dB.

I think you’re “Diving For Noise.” Cranking your speaker or headphone volume up during the quiet bits to see what’s down there. ACX doesn’t care what’s down there. The goal is a nice, well-behaved background sound at normal listening volume.

Your -5dB noise reduction is perfectly valid because nobody can hear it working. My personal favorite is “Noise Reduction of the Beast” 6, 6, 6. It’s easy to remember and nobody can hear that working, either.

There is a recording technique that may prove useful. Try a test with oblique placement of the microphone (B). Don’t announce straight-on. Push the microphone to the left or right and closer. That will reduce any breath or popping sound you may have (none that I found) and the increase in voice volume may make noise reduction not needed.

There is a side issue. Your delivery is, in my opinion, a little too crisp and bright. I applied DVDdoug’s Desibilator (a DeEsser variant) and I like the result.

I used the default settings at -20dB threshold. It’s applied after mastering.

Screen Shot 2021-06-30 at 4.36.44 AM.png

This one is a theater call. It’s not needed like some presentations with SS sounds that will drill wood and shatter glass. It’s completely optional in your case. See what you think. The case for not using it lies in the idea of the less processing the better.

Are you exporting WAV sound files of your raw readings and your Edit Master? That’s highly recommended because you can’t open up an MP3 for editing (your ACX submission) and still maintain the sound quality.


Obsessive Engineer will tell you that your “buzz” tones don’t correspond to common/known wall power sound, but it may be caused by computer fan noise or other electronic devices. Screens fall under this heading.

Iphone screens do this, too, but not as bad.


Since everybody with a pulse is reading from a screen, push your “device” very close to the microphone and make a recording as a test. Experiment with noise and positioning variations. It’s entirely possible your screen and microphone spacing is enough not to make noise at all, but you did complain about a buzzing noise.

Oblique positioning may help here, too. Assuming your device is straight in front for clear reading, that pushes the microphone further away.


I can see the 80Hz (& other harmonics of the 40Hz fundamental), but they are so weak I cannot hear them.

There is skipping, which is audible, most noticeable in the “silence” …

Those are clicking / crackling , rather than buzzing.

Personally I like the crispness :wink:

I don’t notice any “whistling” or over-emphasis of S’s, just a clear and crisp recording. I accept that the amount of “presence” may not be to everyone’s liking, so if I was the producer I might be tempted to slightly reduce the 4 to 10 kHz range using the Graphic EQ effect, but not much - I dislike muffled recordings.

I agree that they are virtually negligible. I could only just hear the 80 Hz when playing quite loudly through a pair of rather bass heavy speakers.

I only noticed a very few of those, and they were all between phrases, so I suspect that they are minor glitches caused by editing rather than anything else. I didn’t find them distracting, but they could probably have been avoided by editing at “zero crossing points” (see: Select Menu: At Zero Crossings - Audacity Manual)

They are on the allegedly “raw” (unedited) recording …

Perhaps River83 meant “not processed” rather than “straight off the mic totally raw” :confused:

Thank you everyone, this is really helpful.

I’ve done another test using the oblique mic placement and I think it’s made a positive difference. This track has been mastered but I haven’t done any noise reduction, although I have added the notch filter, desibiliator and de-clicker (in that order).

This time I can hear the hum (~130Hz).
If you apply a 48dB high-pass filter at 150Hz, twice, the hum is gone …

48db 150Hz High-Pass twice.gif

“…educated university man using magical tones to try and summon the dead.”

That’s how I do it assuming my grandfather’s ball doesn’t work.

Personally I like the crispness

In this case it’s completely an artist call. I’m going on the assumption that an audiobook should sound like someone telling you a fascinating story over cups of tea. It would not be appropriate listening to your Personal Music Player while running on the beach.

I think the last posting sounds practically perfect in every way. I would have no trouble at all listening to a reading in that voice.

Please post the purchase information when you get that far.