FORUMS: list search recent posts

Air Duct sound in b.g.

COW Forums : Audio Professionals

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Craig Alan
Air Duct sound in b.g.
on Sep 27, 2014 at 3:38:21 pm

We've been recording using a Schoeps 641 from an overhead boom. The thermostats are turned off but apparently the building's ventilation system does not allow us to shut off a flow of air through the duct work. The talent does record clear but the low droning sound of air passing through the duct work is annoying. Any way to filter this out either during production or in post? Would a blimp or hum filter of some sort of filter in post or on our SD 302 mixer help?

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index


Richard Crowley
Re: Air Duct sound in b.g.
on Sep 27, 2014 at 7:00:10 pm

Can you cover the HVAC grille during recording? Since you disclosed nothing about the room or the length of the recording shots/sessions, we have no idea whether that would be practical for you.

Or is the noise more low-frequency rumble conducted through the ceiling/walls and not coming out of the grille? If the noise if low frequency, then it is more practical to filter out with a low-cut (high-pass) filter. But broad-band noise (hiss, whooshing sounds, etc.) are impossible to FILTER because they are occuring at THE SAME frequency as the signal of interest (the speech).

Can you get the mic a lot closer to the subject(s?) Like use a mic(s) in front of the subject(s)? Or a headset mic on the subject? Proximity is your friend. The closer the mic is to the talent, the better the signal-to-noise ratio will be. And that includes ambient noise from HVAC. Again, since we know nothing of what you are shooting or why you are using an overhead boom, we don't know how practical this would be for your situation.

Of course you can also look for a more quiet location to record, or cover the background noise with music or perhaps other options depending on what you are trying to do.


Return to posts index

Ty Ford
Re: Air Duct sound in b.g.
on Sep 28, 2014 at 1:38:38 am

Hello Craig,

Richard has provided you with a wealth of possibilities.

I'll add the following. The CMC641 is very directional. Sometimes it's a case of angle the mic away from the noise. A CMC641 can point straight down, even slightly backwards.

Sometimes, a lav on the chest works better because it's on the body, especially if the body is between the mic and the noise. The distance between the lav and the mouth can be shorter than between the CMC641 and the mouth.

Izotope RX3 Advanced (and now new RX4) is very good at canceling out steady noise. You do need someone who knows how to tweek it, but it can be very effective. I also have had impressive results with FCP X's noise reduction in cases where the noise is not that loud.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


Return to posts index


Craig Alan
Re: Air Duct sound in b.g.
on Sep 28, 2014 at 1:55:26 am
Last Edited By Craig Alan on Sep 28, 2014 at 2:18:14 am

Thanks Ty. Been trying to post a video with the noise from the duct but I can't find the thing after I encoded it. Done this before but I guess I forget. Where is the file on the cow?

This Video is being Re-Encoded. Please check back in 5-10 minutes.

nothing happens and unlike when I embed a photo I don't see the code even after that message goes away


Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

Ty Ford
Re: Air Duct sound in b.g.
on Sep 28, 2014 at 2:31:48 am

Hi Craig,

Boy, you ask a very good question. I'm pretty mystified by that process myself. Don't know why it has to be so hard.

Have you tried something simple like dropping a Youtube or other link in?

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Sep 28, 2014 at 4:29:46 pm

cow server went down last night. here it is.

studio noise



Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index


Richard Crowley
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 12:49:48 am

Sorry, a recording of noise by itself is actually useless without the reference to the normal signal level.
Not clear why you would want to record in such a noisy room? Is audio not important to the production?
We hope that level ramp at the beginning is not an indication that you are using auto-level here?


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 2:03:23 am

I increased the gain of the noise in FC so you could hear it clearly in terms of a possible filter that would help reduce it. It's not my choice to have air continue to be pushed through the ducts even when the thermostats are off. It's a studio; it's where we shoot.

I will be meeting with rep from thermostat company to see if something can be done to isolate the so that the system turns off completely when we turn it off.

here's an audio clip with voices.

studio noise 2



not auto gain. left and right set independently.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

Richard Crowley
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 4:40:16 pm
Last Edited By Richard Crowley on Sep 29, 2014 at 4:41:10 pm

How many people are you trying to mic with a single hypercardioid?
It sounds to me like your basic microphone scheme is completely inappropriate for what you are trying to do.
A hypercardioid mic is appropriate for ONE person when you keep it aimed directly at their mouth.
A hypercardioid mic is NOT appropriate for picking up multiple subjects, ESPECIALLY if you are attempting to use it in a FIXED deployment.

Your expectations of covering multiple people in a noisy room with a distant, fixed hypercardioid is almost a text-book case of worst-case conditions.

The main problem here isn't the air duct noises, it is the microphone deployment.


Return to posts index


Craig Alan
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 9:37:37 pm

The hypercardioid is aimed at only one person in a fixed location aimed at her mouth as close as possible, just out of frame. The male voice is miked with a countryman headset and he is off camera. What you hear is before any editing. Not sure what you are hearing that sounds that awful. But I'm not a pro audio tech and this is a no budget film in a school production studio with a noise problem that I'd like to address. The voices sound fine to me. But I'm all ears if you want to give specific advice on what to listen for or mike placement etc.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

Richard Crowley
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 11:57:22 pm

It sounds distant and reverberant to me. The microphone is too far away from the subject for a room with those acoustics. And by acoustics, I mean BOTH the ambient noise AND the reflective surfaces (walls, ceiling, floor, table, whatever).

This sounds like a casual interview. Since you didn't include the picture here, we have only the audio track as evidence, so you are privy to a great many more details here than you have disclosed to us.

What is the justification for using a microphone so far away on a boom out of the camera frame? I would challenge the producer on that one. What is more important here? NOT seeing the microphone (WHY?) or getting good sound?

Can you use a distant mic technique like you are using? Sure, in the proper acoustic environment (but that room isn't it.)
Can you get decent sound in that room? Sure, with the proper mic technique (which is NOT a distant hyper, IMHO).

If you listen to JUST the sound from the off-camera interviewer's headset mic, how is the signal (speech) to noise (HVAC sounds) ratio?


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Sep 30, 2014 at 12:29:23 am

Got it. Thanks. It was an interview of sorts - an analytic session. The mike was fairly close, about 2 feet. I am shooting with 3 cameras the widest being a mid shot which determined the distance that the mike needs to be. I really want to kill that sound. The room does not have good acoustics or any treatment and you have a well tuned ear. But that fan or hum or whatever it is is the thing that is really annoying. With lots of back ground noise ,like during classes with three teams shooting you really don't notice it much. But after school more serious shoots you can't escape it.

[Richard Crowley] "If you listen to JUST the sound from the off-camera interviewer's headset mic, how is the signal (speech) to noise (HVAC sounds) ratio?
"


still bad and I've tried aiming the hyper at different places in the room to try to find the source or better acoustics and it makes little difference. That's why I though a filter might do the trick.

For dramatic reasons we can't have the mike in the shot. But even with the countryman headset right near the mouth I can hear the b.g. noise. I will try to get our HVAC expert over - I'm wondering if the thermostats are broken. Maybe the fan does not turn off. Maybe an adjacent room could be turned off. The sound reminds me of when a fan in a computer is whooshing through cheap plastic parts and its driving you crazy when you are editing.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index


Craig Alan
Re: Air Duct sound in b.g.
on Sep 30, 2014 at 6:25:26 am

when we were striking today at 8:30 pm we realized the room got quiet. so something is running that can be shut off.

huge difference.

I'll try to get help on that.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

Richard Crowley
Re: Air Duct sound in b.g.
on Sep 30, 2014 at 5:30:40 pm
Last Edited By Richard Crowley on Sep 30, 2014 at 5:33:30 pm

Two feet away is NOT "fairly close" under ANY conditions. And especially in a small, reverberant room. Two feet is rather at the most extreme end of the working distance you could expect. I think you may have unrealistic expectations of what these microphones can do.

I fear you completely missed my question about the headset mic. My understanding is that the headset mic was on the interviewer who was off-camera. When you listen to JUST THE HEADSET MIC (without the hypercardioid mic on the subject), what is the signal-to-noise ratio and quality of the audio? Since the microphone is a few cm from the interviewer's mouth, I would expect the track to be almost completely absent of the room/ambient problems.

Of course, we are assuming that you are recording the interviewer's mic and the subject's mic on separate tracks so you can isolate them and listen to them separately. If you are mixing the mics together during shooting, that is another practice you could avoid to help you deal with recording audio in a hostile environment.


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Oct 1, 2014 at 5:43:41 am

Richard I got as close as I could and still be out of frame. The two mikes were on two different channels and
Listening to just the channel with the headset mike you can still hear the hvac noise . The room is not that small. 51 x 39 feet with a light grid at 15 feet high and ceiling at about 20 feet. But virtually no sound treatment. I've recorded in this room without the noise and at that distance I've been pleased with the audio. I'm sure you could detect less than ideal acoustics. I've never read anywhere that 2 feet from a talent's mouth is too far to place a boom mike. I had the talent on two close ups and a mid shot. The overhead cam was the only one that I could see the mike dipping in a bit on a monitor. I lifted it just out of frame. Even with a quiet voice the mike picked up her voice at decent levels. I can't use a headset on this talent. Now if the headset mike didn't pick up the noise I might start thinking about hiding a lav on the talent. But my need right now is to get the hvac fan to turn off when we are shooting. That won't fix the room acoustics but no one will spend money on doing this since we are designing a new studio and have an audio expert to consult on sound treatment. This studio is EOL. If you thought maybe hanging blankets around the talent or some other make shift treatment would help I'd consider it.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index


Craig Alan
Re: Air Duct sound in b.g.
on Oct 1, 2014 at 6:19:03 am

Sorry. I just took a ruler and measured approximately where I placed the mike and it was closer to one foot than two.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

Richard Crowley
Re: Air Duct sound in b.g.
on Oct 1, 2014 at 12:59:09 pm

It doesn't really matter exactly how far away the mic was. If the resulting audio signal contains such a high ratio of environmental noise, reverb, etc. then the combination is sub-optimal.

But there are a wide variety of factors at play. Such as expedience of production. For example if you are doing "run-n-gun" chasing a corrupt bureaucrat down the steps of the courthouse, there is a different expectation for audio quality. And "reality television" (which is anything but, IMHO) has somewhat changed audience expectations. Although, they go to rather extreme lengths to maintain broadcast audio quality with dozens of wireless body mics, etc.


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Oct 2, 2014 at 1:50:55 pm

Not a fan of reality shows and the fabricated conflicts and plot points that get repeated over and over. We can't do much about the room characteristics except build a better studio. But I am hoping to get the HVAC system fixed so we can shut down that fan noise which is amazingly persistent regardless of mike placement, type of mike, and gain levels. For the no budget films we shoot I've been pleased with the sound quality on some of the shoots. I have a poor ability to estimate distances but I did get the overhead hyper closer on our last shoot and it helped but Hvac noise just seems to reverberate all through the studio. I was told a HVAC contractor was coming to repair it and hopefully get the AC working in the storage room where we charge our batteries. Right now I'm just looking for a post filter to remove much or the HVAC sound that will play nice with FCP X. I'm trying out FC built in noise reduction - not in the audio effects window but I assume that's what it is anyway. It seems that it needs to render before you can hear the final result. So I'll try it on small portions of clips before using it on entire clips. Will try John's suggestion as well.

Since the hyper is aimed down would adding a rug underneath the talent help at all?

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index


Craig Alan
Re: Air Duct sound in b.g.
on Sep 28, 2014 at 4:43:41 pm

[Ty Ford] " I also have had impressive results with FCP X's noise reduction"

what is 'noise reduction' called? don't see it under audio effects.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

Richard Crowley
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 12:54:24 am
Last Edited By Richard Crowley on Sep 29, 2014 at 12:56:45 am

Software noise reduction is only a last-ditch method of salvaging otherwise useless dialog for something where quality is not important. It should NEVER EVER be used as as substitute for recording the audio properly to begin with. That includes selecting a quiet-enough location, selecting the proper microphone for the job, and positioning it at the proper distance form the subject.

Having to apply software noise-reduction in post production is an admission of major failure during production. IME, I categorically reject the very notion of trying to do this as a pre-planned part of any production. If audio is important, then select a location that is not audio-hostile.

If that categorizes me as hard-nosed and inflexible, then so be it. If the producer wants to compromise on the audio track, then they can find somebody else to do a marginal job.


Return to posts index

John Fishback
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 2:16:54 am

I just upgraded to iZotope RX 4 Advanced. It's amazingly good. There's a module that does adaptive dialog noise reduction. You can almost set it and forget it. I believe this module is now available in the regular (and less expensive) RX 4. I recently used the whole program to restore a 60 year-old vinyl recording and while that takes a bit of effort, the results are outstanding. RX roundtrips from Pro Tools, but also is a standalone app. At the moment there's a bug if you want to send from FCPX, but they're working on that. I had slightly boomy sound in a video setup recently and the De-Verb module cleared it right up. It's a great piece of software. BTW, I'm not connected in any way to iZotope, but have used the software since its introduction and it just keeps getting better.

John

MacPro 8-core 2.8GHz, 16 GB RAM, OS 10.9.4, QT10.1, Kona 3, Dual Cinema 23, ATI Radeon HD 5870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCP-X 10.1.3, Motion 5.0.7, Compressor 4.0.7
FCS 3 (FCP 7.0.3, Motion 4.0.3, Comp 3.5.3, DVDSP 4.2.2, Color 1.5.3)

Pro Tools HD 10 w SYNC IO & 192 Digital I/O, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec DSP Monitors, Prima CDQ120 ISDN


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 3:15:35 am

Thanks John. Do you think the noise in my clip can be handled in the lite version? I have a bit of funding left for this year and could cut an item to make room for the lite version. I would need it to round trip with FCP X though. I guess I could export a master of each clip from Final cut. Open it in RX 4 then reimport into FC??? How much of a learning curve? I have not worked with pro tools or any pro audio software.

Can you upgrade if you use the lite version and want to step up? Or do you pay the whole amount for the pro version?

Mean time I'll do what I can to get someone to turn off the system. It's also possible that the ducts are picking up noise from an adjacent room in that building. There is a garage next door. They may have something running in there. We are designing a new studio which will be built in the next two years and we're bringing in an audio specialist to help with the design.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

John Fishback
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 4:21:17 pm

I think it would work very well with your clip. You can get a trial version of RX4. The dialog de-noiser is easy to understand. Other modules are more complex. There are some good tutorials available. You will have to export the audio from your project, import to the standalone app, de-noise, then import the file back to FCPX. There are upgrade paths, but I don't know if you save by upgrading from RX 4.

John

MacPro 8-core 2.8GHz, 16 GB RAM, OS 10.9.4, QT10.1, Kona 3, Dual Cinema 23, ATI Radeon HD 5870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCP-X 10.1.3, Motion 5.0.7, Compressor 4.0.7
FCS 3 (FCP 7.0.3, Motion 4.0.3, Comp 3.5.3, DVDSP 4.2.2, Color 1.5.3)

Pro Tools HD 10 w SYNC IO & 192 Digital I/O, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec DSP Monitors, Prima CDQ120 ISDN


Return to posts index

Craig Alan
Re: Air Duct sound in b.g.
on Sep 29, 2014 at 9:38:59 pm

Thanks John. I'll contact the company and see if how they are coming with the Round trip to FCP X fix.

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.


Return to posts index

David Patterson
Re: Air Duct sound in b.g.
on Nov 25, 2014 at 6:31:39 pm

If the luxury of perfect recording environment acoustics isn't available, definitely consider audio surgery in post. When no other options exist, I employ parametric EQ, noise filtering or audio gate tools in Adobe Audition, and find they can go a long way towards minimizing background noise issues. I think your audio could easily be improved in post.

I advise not trying to remove the background noise completely, as this will encroach on frequencies of the dialog and some natural ambience that you may need to retain. This process requires experimenting with settings to get good results, so do not expect a quick and simple fix. However, in cases where you are stuck with bad background noise, some fixing in post is certainly worth trying.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]