Can't filter grinder noise completely

Audacity 2.0.2
Windows XP Professional Service Pack 3 Version 2002

As the title says, I have an audio recording I made for a school assignment, but starting at 1:40 lasting through to the end has a very loud grinder noise from a nearby construction project. I offered to filter it with audacity, but I found it to be harder than I had expected, even with the noise on a seperate recording. I read the tutorials on noise removal, but no matter how much I tweak the settings the sound will either remain or the remaining audio will be rendered too scrambled to use. Attached to this post are the two audio files, the first one of the recording itself and the second one of the grinder noise. If someone’d be able to filter the grinder noise without too much loss in the quality for the rest of the audio I’d be very grateful.

Note that there are two recordings of the grinder noise: the first one is just the clean recording with some other sounds in the background, most notably the bouncing of a basketball, and the second one is amplified to match the volume of the other recording better and has the bouncing sounds filtered out.

Also, if nessecary I can save and post some of my failed attempts with the accompanying settings too.

Recording (grinder noise starts around 1:40)
Unfiltered grinder noise
Filtered and amplified grinder noise

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You have probably gone about as far as you can.

Noise Removal doesn’t “know” what noise is. All it does is take your profile and try to create sharp, precision filters that remove it. Then, without forgetting the profile, it tries to use the same filters on your show. If your show and the profile have a lot of the same tones and sounds in it, the valuable sounds will start to act funny and sound weird. That’s why there are so many adjustments. It’s not a set and forget tool. The Smoothing control in particular is magic. That’s the one that tries to shut down noise reduction during voices so they don’t sound like they’re from Mars. The down side is the voices don’t get noise reduction.

It’s much worse if the noise is moving. As long as the grinder stays at exactly the same pitch and you don’t have Auto Gain running on your camcorder, you should be able to do an OK job. If the grinder is much louder than the show, you’re dead. You’re also dead if you got there just as the grinder is starting up. That’s a moving sound (constantly changing pitch) and Noise Removal doesn’t work on that at all.

I predict [holding fingers to forehead] you were doing an interview with the microphone on top of the camcorder. Please note that when the big kids do this, they either wear a tie-tack microphone or hold a serious directional microphone in order that the voice is always much louder than the environment.

For teleproduction:

Boom microphone…

Shotgun Microphone…

Sound kills more productions than video. Field production is particularly difficult. “OK, Cut! Let’s wait for that jet to go over.”


Thank you for your help! Too bad it can’t be done like this, but at least you can hear what we’re saying (although you probably can’t due to us speaking Dutch instead of English) and in the worst case scenario we can do it over somewhere else.

Also, you took some pretty good guesses there. We were indeed doing an interview and the microphone was indeed integrated into the camcorder, although I’m not sure about its exact position.

Anyway, thanks again for your help and your time to give me such a thorough explanation.

I poke fun at our two Little Dutch Boys (both well over 6’ tall) that spoken Dutch sounds like pots and pans falling down the stairs.

As a training exercise, I’d say this was a success. You learn nothing if the show goes smoothly. If I or the producer was in love with the location, we would stop recording when the grinder was active and pick it up again when it was quiet. Edit our brains out in post production to splice the successful chunks into a show.

See, there’s even a way to rescue what you were doing, just not that particular clip.