Topic: Mics picked up AC (low frequency swell) - editing suggestions?

[robotaper]

Seeking input or possible solution for doctoring a recording in post.  I recorded a bluegrass show, indoors.  I ran the caps without wind screens, at an approximate height of 9'.  Listening to the recording I noticed an occasional "rumbling" coming through.  It's very subtle, and almost not noticeable except between songs.  After investigating further I've determined my mics picked up the exhaust from the air conditioner of the theater (I noticed during the show that it seemed rather cool).  The theater has no fans, and the ceiling is a good 30'+ high so I didn't think "wind" would be an issue.  I've learned my lesson for future recording at this theater.

Any suggestions for removing the sound of the "wind" (i.e. low frequency rumble) from the recording?  I realize I probably wont be able to remove all of the "wind" sound, however since it appears mostly as a low frequency I was considering using an EQ or High Pass Filter of some sort.

It's a shame because the recording sounds great, with the exception of the wind damage.  Any suggestions from those with previous experiences will be appreciated.

[ScoobieKW]

I'd go with your eq/high pass filter idea. A bit more work, but selectively apply the correction to between songs if you are finding that you are losing to much from program material.

[page]

I'd go with your eq/high pass filter idea. A bit more work, but selectively apply the correction to between songs if you are finding that you are losing to much from program material.

2X

tweak the Q value and rolloff start to where you find it eliminates the majority. Also, remember it's better to under-do rather than over-do.

[stevetoney]

FWIW, I once recorded Chris Duarte at Dinosaur BBQ (best ribs in the universe!) up in Syracuse NY and had an annoying background buzz in the recording for the first part of the show.  I couldn't figure it out until I remembered that there was a neon sign maybe three feet to the left of where I was standing that was turned off part way through the show.  Just a comment on other things besides AC for things to avoid inside the venue.

[Todd R]

MMmmm!!!  Dinosaur BBQ!  I haven't had that in twenty years, my mouth is watering just thinking about it.

Live music at Dinosaur BBQ, who would've thought it.  I left Syracuse in 1991, man that town has changed!

[stevetoney]

MMmmm!!!  Dinosaur BBQ!  I haven't had that in twenty years, my mouth is watering just thinking about it.

Live music at Dinosaur BBQ, who would've thought it.  I left Syracuse in 1991, man that town has changed!

I can't comment on how much Syracuse has changed, but for a city its size, I really like it.  I spent the better part of 3 years there, from 2002 to 2005.  Actually I worked at the plants up in Oswego, but had an apartment for weekday living in Baldwinsville and then drove back home on weekends to Balto.  OMG, the winters up there are ferocious and I've never seen as much snow as I saw when I drove home after work and witnessed the lake effect that would dump on Fulton, NY.  Most-snow-evah!

[Fried Chicken Boy]

Dinosaur BBQ (best ribs in the universe!) up in Syracuse NY

Dinosaur is damn tasty and probably the best 'cue in the northeast, but I'm sure there are a lot of folks (ie: KC, Carolina, Texas, Memphis) that would take exception to that statement.

Back to the original thread, I ran into the identical situation when I flew mics sans windscreens and didn't realize how powerful the venue's A/C was.  Picked up "gusts" all throughout the quiet parts of the recording.  I used a graphic EQ to find the offending frequencies (somewhere below 100-150 Hz, if I remember correctly) and notched out the audible rumbles.  Time consuming and laborious, yes, but made me much happier with the recording.  Suffice to say, I won't run mics anywhere now without windscreens except in a studio.

[stevetoney]

Dinosaur BBQ (best ribs in the universe!) up in Syracuse NY

Dinosaur is damn tasty and probably the best 'cue in the northeast, but I'm sure there are a lot of folks (ie: KC, Carolina, Texas, Memphis) that would take exception to that statement.

I know it and I thought about that when I typed it.  Since I've never been there, I can't DQ Texas or KC from the list based on my experience, but Dino stands toe-to-toe with anything I've ever tasted in the Carolinas or Memphis. 

[F.O.Bean]

Another reason why I ALWAYS suggest that you should ALWAYS have windscreens on your mics, whether indoors, or outdoors

[mattmiller]

Another reason why I ALWAYS suggest that you should ALWAYS have windscreens on your mics, whether indoors, or outdoors

I refuse to run without them.  I've been burned too many times and now realize that no matter HOW still the air feels to me, the mics can tell a lot better than I can.

[robotaper]

Thanks for the input.  I agree on the windscreens point.  I've been running w/o indoors and have been pretty lucky up until now.  But it's been just that, luck.

I'm going to see what I can do to eliminate the lower tones created by the breezy conditions.  I think the recording is more then salvagable so it's worth taking the time to zero in on the trouble spots.

I'm hungry for barbecue for some reason...Thanks again.

[gratefulphish]

If you can see the particular frequency using any form of spectrum analyzer, like in SF, you can then draw a very or fairly narrow notch filter which should remove the majority of the offending noise.

As a further tip on avoiding this problem, always look for the air conditioning vents, and/or fans in a venue when setting up.  I usually hold a lighter up a few inches in front of my mics.  If the flame is flickering around a lot, on go the windscreens.  If the flame is calm (while you know the AC is running) then you are probably okay without them.  I prefer not to have the high end attenuation of the windscreens when I have the opportunity to avoid it, but then I also have to protect my caps in certain clubs down here where there is so much smoke that I want them on no matter what.