Recording in a space with air conditioning / (ceiling) fans.

Special Interest Groups Recording Techniques
1

Hi All,

I make recordings using 2 Oktava MK-012 microphones, connected to a Edirol UA-25EX. I obviously use Audacity too :slight_smile:

The problem is that many of the places where I record have air conditioners or (ceiling) fans running constantly and at full capacity. Both generate quite a bit of air flow that is being picked up by the microphones. Needless to say this ruins the recording.

I have tried using the standard pop filters, but it is just not enough.

Any suggestions are welcome!

Regards,
Peter

2

Have you tried a windshield?

Something like Rode’s deadcat:

3

Many people make wind screens like that. Read the reviews. The furry ones tend to work really well. Also, nobody does live movie capture without the 100Hz roll-off filter in place. Most of the wind rumble and thump is below 100Hz and nobody’s voice is that low.

http://www.fullcompass.com/product/305006.html
http://www.shure.com/americas/products/accessories/microphone-accessories/problem-solvers/A15HP-inline-high-pass-filter

Here’s the filter in Audacity.

http://kozco.com/tech/audacity/100Hz_Rumble.jpg

It’s dangerous doing it in post. If you have severe rumble because you captured it that way, it will cause cracking distortion in the show and it’s permanent. You can’t fix it later.

Koz

4

Hi All,

Thanks for the advice!

I have been playing with a high-pass filter as well (steep roll-off at 50 Hz.). That seems to work fairly well, but I’ll try the filter mentioned.

Regards,
peter

5

That’s what this is. You can use the Audacity High Pass Filter set to 100Hz and get similar results. Fudge that number. I have a mixer that can switch between 80, 100, and 120. 100Hz is the classic one and that’s the one built into the Shure Brothers plug-in device.

http://store.shure.com/store/shure/en_US/pd/productID.104210700

Being compulsive, I reconstructed the Shure curve using the Audacity equalizer tools, but you don’t have to do that.

We almost always capture voices using a filter. You never notice it in the movies, because the music and explosion effects cover it up and are put in as a post-production process. Capturing voices “flat” and without the filter is asking for trouble.

http://kozco.com/tech/audacity/pix/Boom.jpg

Koz

6

This is a really bad recording, but it illustrates what you can do with a simple roll-off and gentle noise reduction.

https://forum.audacityteam.org/t/how-can-i-remove-loud-ventilation-fan-noise/18749/4

It’s a given that you need a music system that will go down that far in order to hear what you’re doing. “Computer Speakers” won’t do it. Good Quality headphones are called for, or a very serious sound system.

I have Koss Pro4AA headphones and Boston Speakers with Crown amplifiers and a KLH Sub.

Koz

7

@Koz - So, if you’re using a high pass filter in Audacity, you do it BEFORE recording, is that right? That it won’t work as well if applied after the fact?

But you’re saying that - for booming voices for, say, film - it’s standard to use an in-line high pass filter?

Thanks.

8

You don’t do anything in Audacity before recording… If you haven’t recorded anything yet you don’t have a recording to apply an effect to… and audacity can’t do anything in real time.

Many mics have a builtin high pass filter (they often call it low cut filter). Maybe that’s what Koz was referring to…