Dealing with noise from lights

[Plunkett Sound]

I've been having a look for threads specifically on this and I couldn't find any. So I thought I'd kick it off:

How do you deal with excessive noise from lights?

 

If a light is giving your trouble, what factors do you check to make sure it is as quiet as possible?

 

What are people's views on the ettiquette of dealing with such problems? How much should you ask for/expect from sparks and camera?

 

The obvious things are to find out whether the lights are on dimmers or not. I've found the Flicker Free setting on certain lights can cause buzz as well. The choke from a light can usually be put around a corner to block its noise, however I've found that the light itself is more often the real source of noise.

 

And how about dealing with massive 5K lights? Granted they're usually outside a window in order in simulate sunlight but that doesn't always mean you can't hear them.

 

So what tricks do people use to deal with noisy lights? I'd love to hear your input.

[David Waelder]

This is a situation where the EQ capabilities of your mixing board may be very useful - not so much to correct the problem as to identify if it really is a problem.

 

Sometimes hum from lights falls right into a voice spectrum and can be a real nuisance. However, much of the hum from lights is fairly high frequency and can easily be remedied by post.

 

Using the high frequency dial on your EQ, try to dial out the offending sound. Check your impressions using the mid-range EQ. The mid-range typically has two dials, an intensity (maximum boost - maximum cut) and a frequency selector. Using those two knobs, you can often identify where the buzz or singing noise falls. Simply set the intensity knob for maximum cut and sweep the frequency knob to find the point of maximum reduction. Or, go the reverse and set maximum boost and try to find the frequency where the noise is most offensive.

 

If the noise is broad-band or falls at 500 Hz, you have a problem. But if the noise falls into a narrow band around 4 kHz, then it is well outside of any normal (not singing) voice and you can be confident that post can successfully remove it.

 

After running these tests, return your EQ settings to normal. You want to investigate the problem, not try to dial it out with your limited equipment. (And without the "UNDO" button available to post.)

 

David

 

Of course, always review the issue with the gaffer. If a more quiet example of an instrument is available, it's always preferable to swap out the noise source rather than rely on "saving it in post."

[Michael Miramontes]

Dang David, that is a great way of dealing with it. 

 

I was just going to say throw a furni-pad over the shitty ballast. 

[David Waelder]

Furni-pads can help tamp down a troublesome ballast but, if you leave the pad on the ballast, it will sooner or later cause it to overheat.

 

Good, maybe, to get a quick close-up, not so good if you need to play the whole scene.

 

David

[chrisnewton]

 Diplomacy. It's a matter of teamwork. If you have a good working relationship with the grip and electric department, they can help solve the problems you describe by swapping out offending ballasts or noisy fixtures, placing the generator at a suitable distance etc. It's supposed to be a team sport, but if the rest of the crew don't see it that way, you are pooched. Experienced crew members will be aware of the challenges to the sound department and help out. Less experienced people may not even have thought about lights causing sound issues. Let them know about your problems. Crew members who know about the problems and refuse to do anything about them, or are too lazy, are dickheads. Let the assistant director (or whoever is in charge on your shoot) know about your problems in a professional manner and you may or may not get the support you need. Always take the high road. As David points out, sometimes the problem  isn't as bad as you think it is. Don't lose sleep over it.

Chris

[RPSharman]

It's usually the old and poorly maintained bigger lights which cause the biggest problems.  Right in the mid range.  Try to get to it quickly and see if they have another on the truck. Our gaffer just smacks it a few times.

 

HMIs should always be on silent when recording dialog.  No reason not to be.  These are often used on commercials, so frequently show up to set already on flicker free setting.  Have a look at the ballast, and if it's set for flicker free, kindly ask an electrician to swap it over for you.

 

HMI ballasts or dimmers with fans should be off set.  There's a reason they come with a head feeder.  It's not so you can coil it up nicely under the stand and keep the ballast on set.  Dimmed lights may be noisy, but taking the dimmer to 100% and back down to the desired setting sometimes helps a bit.

 

Another issue are hand squeezers (consumer dimmers) used on practical lights on set.  These can create noise.  If you find the culprit, ask if they might have a Variac (pro level variable AC dimmer) available to use instead.

 

They know if a light and/or dimmer is noisy just as much as you do.  If you use your best diplomatic skills, there should be no problem finding a solution to a noisy light.  It's only when faced with something they want to use, and will not swap, which makes you have to decide how much of a problem it really is.  Then you have to chat with the DP.  But that's a whole other discussion.

 

Robert

[Philip Perkins]

+1 for diplomacy.  I try to suggest we find a way to get the lighting effect they want in a quieter manner, if that is possible.  It usually is, if there is an atmosphere of cooperation.  (Longer ballast head cables, blocks so equipment is not directly "visible" to mics if possible etc.)   Yes, there are some lighting people who will not hear about any of this and will not help--sorry to say that in my experience they've mostly been from LA!  If you hit a wall like that then there's no use hosing the vibe of the set with a scene--put it in your notes and move on.  I've found that while a gaffer may refuse to countenance any modification to his setup for sound, his assistants may take pity on you and try to help if you haven't been confrontational about it and have been cooperative otherwise (ie the famous "location of soundcart=new location of key light", or you haven't already made them lay a lot of extra banded to get the genny far away).  A lot of the attitude about whether to help sound or not in this way comes straight from the director and the DP.  On commercials, ironically, it is often the clients who first notice an unfixed sound problem from lighting, and then, if you are publicly asked if it's a problem, your diplomacy skills will be on display (ie trying to get better sound without publicly embarrassing other key crew by making them look careless....you have to live in this town, remember?).

 

philp

[Jack Norflus]

Like already mentioned the best way to eliminate the noise is to get rid of the offending light/ballast. Though that may not be as easy as it sounds.
Given that I have eliminated lighting noise with my Nomad by using the notch filters.

I was recently on a show that I had this same issue. The show was going to have no audio post, so my choice was to either leave it there or eliminated it. So I eliminated it. If the show was going to have audio post I could have either eliminated it (depending where it is) or I can find the frequency and note it so post will find it easier to deal with.

With all Zaxcom recorders there is a dual notch filters on the input channels. Each filter can be independently adjusted to provide a notch at two specific frequencies and on Deva and Fusion you can even adjust the Q values. You can dial the notches to the offending frequencies. The filters can provide a 60dB notch that can totally eliminate lighting noises, motors, or most other "constant" noises. The filters can often even be used in the middle of the vocal range without any noticeable change to the audio with the exception of the elimination of the lighting noise.

I personally find it a nice tool to have even though I may not use it that often.
 

[Earmuffs]

+1 on the Zaxcom notch filters. I've used them very well to eliminate generator noise but less successful in eliminating the variac dimmer noise but maybe it was just me. In the end I just had to be diligent in getting room tone.

[Philip Perkins]

Like already mentioned the best way to eliminate the noise is to get rid of the offending light/ballast. Though that may not be as easy as it sounds.

Given that I have eliminated lighting noise with my Nomad by using the notch filters.

I was recently on a show that I had this same issue. The show was going to have no audio post, so my choice was to either leave it there or eliminated it. So I eliminated it. If the show was going to have audio post I could have either eliminated it (depending where it is) or I can find the frequency and note it so post will find it easier to deal with.

With all Zaxcom recorders there is a dual notch filters on the input channels. Each filter can be independently adjusted to provide a notch at two specific frequencies and on Deva and Fusion you can even adjust the Q values. You can dial the notches to the offending frequencies. The filters can provide a 60dB notch that can totally eliminate lighting noises, motors, or most other "constant" noises. The filters can often even be used in the middle of the vocal range without any noticeable change to the audio with the exception of the elimination of the lighting noise.

I personally find it a nice tool to have even though I may not use it that often.

 

It's interesting to hear about those notch filters, and totally eliminating all those frequencies.  When I do this in post, where I have a visual reference of what I'm hearing (reNOVAtor, RX etc) I find that I need to attack far more than 2 frequencies of treatment to begin to get a handle on the offending noise, and I am not using tools that merely reduce a certain frequency zone.   In the case of HMI noise one can see the audible harmonics of the sound laddering up from something like 250 Hz all the way to as high as 15kHz.  This is also very true of motors, fluorescent lights, and other constant noises.   Are you saying that once you've attacked those noises with your 2 filters that I would not see or hear any artifacts of those sounds left in the recording?  And that cutting a notch as deep as 60 db in the middle of the voice range of talent that is wide enough to encompass a noise rich in harmonics has no audible effect on the voice, at all?

 

philp

[Henchman]

Please guys. Don't be using EQ's and notch filters in your recordings.

We can Fx those issues ourselves in the proper environment. The dubstage.

[VASI]

Please guys. Don't be using EQ's and notch filters in your recordings.

We can Fx those issues ourselves in the proper environment. The dubstage.

[stevegrider]

One key element to solving noisy light and ballast problems is walking the set as soon as possible. Many times sitting at the sound cart, you don't know there is a problem until first rehearsal. All the hustle and bustle of a busy set can mask noise until all is quiet. I try to walk around as soon as all lights are up. Giving the crew a little extra time to find a replacement for a noisy piece of gear goes a long way courtesy-wise. Asking them to scramble after first rehearsal is fun for no one.

[Philip Perkins]

One key element to solving noisy light and ballast problems is walking the set as soon as possible. Many times sitting at the sound cart, you don't know there is a problem until first rehearsal. All the hustle and bustle of a busy set can mask noise until all is quiet. I try to walk around as soon as all lights are up. Giving the crew a little extra time to find a replacement for a noisy piece of gear goes a long way courtesy-wise. Asking them to scramble after first rehearsal is fun for no one.

+1

 

philp

[Simon Hayes]

1. During Location Scouts and initial meetings with the Gaffer ask him to have the lighting company supply double header cables on each HMI lamp and let him know you require ballasts to be off the set and never in the same room you are shooting in at a location.

 

2. Ask the DP before testing if he will allow the lamps to be run on their silent setting when shooting 24fps/60hz (or 24fps/50hz in Europe) that is what the 'silent' setting is designed for.Of course,when the camera shoots high speed the ballast can be run at 'flicker free' but usually this is not on sync sound shots.If the DP feels uncomfortable about this (he will only feel worried if he is inexperienced)

then ask him to run tests during the camera testing period to check that at 24fps camera speed there is no flicker.

Assure him that you,the Gaffer and the 1st AC will be responsible for the ballasts being set to flicker free when he shoots high speed.

When he agrees to this speak to the 1st AC and ask him to let you know EVERY time the camera speed is changed.

 

3. If the ballast HAS to go in a room on location that you are shooting in because it is impossible because of access problems to get it off the set then it HAS to be covered with a sound blanket and/or a rubber backed piece of carpet.Put your trainee/intern on the job and explain to the Gaffer that your guy will stand with the ballast and cover it only while the camera is rolling so it does not overheat.

 

4. If the actual head of the lamp is noisy while the ballast is set to 'silent' ask the Gaffer to swap it out,mark it up and send it back to the lighting hire company and get it changed otherwise you will face the same issue the next day...........

You need to establish EARLY if it is noisy,DO NOT leave the conversation until it is too late.

 

5. Sometimes changing the bubble (bulb) of a noisy head will quieten it down,and other times a short sharp smack on the lamps casing from the handle of the boom pole will stop the resonance within in it (especially on tungsten).  *If the gaffer is your friend he may let you try this approach ;-) but you should obviously ask him before engaging in such an activity............

 

 

6. Never EQ it out on set (as David Waelder says).

 

7. Never use EQ or a sound blanket when the correct approach is to move the ballast.Look for a fix,not a 'band aid' to avoid the conversation with the gaffer.

 

8. If all else fails and the head is noisy you can sometimes reduce the noise by flagging the sides and rear of the head with sound blankets.

[Alexander Burstein]

A common theme in these responses is the support from another department. Mostly lighting, sometimes dealing with the DP directly. Since a boom operator is usually your eyes on set, it would help to have a solid boom op on your team with great diplomacy skills.

Many times I get confused looks from inexperienced electricians when I make some of the mentioned notes or requests. In cases like this I ask nicely, and try to explain my problem. Sometimes they react supportively and sometimes as people have mentioned, they don't give a crap.

If you can start as early as location scouting like Simon said i would guess you'll get more results and respect.

[Jim Rillie]

I try to get a very dedicated room tone for post, and put a note in metadata about it.

+1 on Simon's well thought out recommendations.

 

Regards,

 

Jim Rillie

[Marc Wielage]

Dang David, that is a great way of dealing with it.  I was just going to say throw a furni-pad over the shitty ballast. 

 

I've used C-stands placed around the shitty ballast to "containerize" the noise a bit. It will definitely overheat if you just throw the blanket over it.

 

Amen to Simon Hayes' advice -- assuming you have a cooperative G&E department and sufficient time & money.

[Pablo]

+1 for Simon,

I worked in a production some time ago where the hmi 5k was killing me, it was in the 13k-16k neighborhood so I thought that I could record that constant frequency an later on post could phase it out of the original recording. It didn't worked for me.

Talk with other departments.

Make sure G&E has spare cables an they don't put the ballast close to set(or as far as possible)

If nothing works, write it down and talk with the AD

[Sound Dude]

This is such a per-case problem.  Never take away from your EQ!!  Always keep communication open with your gaffer and his crew know their names and know the lights!!!  It always helps to know about the equipment that is causing you problems that way you can quickly tell the gaffer which head or ballast it is.  scout the loctation, stage or off the lot.  Ask them to move ballasts if they are too close.  Never move the equipment on your own or touch the settings this will ruin your relationship with the crew!! 

 

ON STAGE

 - if you are on a stage you should have them run the ballast all the way off stage. that means outside! don't let them bullshit you with line loss Ive had electricians try to tell me that if they run that much head feader it wont work. this goes back to knowing the equipment.  

 

- if its the head that is the problem.  start with the silent mode. from there ask the gaffer to ramp the ballast up and down this will sometimes help with the high frequency singing we all love so much. If that still does not work I will go as far as to ask them to try another head. this all comes from the experience of hearing certain lights and knowing that it should and can be quieter than that. if they dont have another head I will attempt to deflect some of the noise with some grip help at the back end of the light. either a 4x4 
Bounce board and deflect some of the sound away from where we are shooting or positions some 4x4 floppies or sound blankets on the sides and back of the light to try and absorb some of the sound.  dont forget the old tap tap with a hammer or even a heavy fist. seriously that works sometimes with older hmi (ask before doing this)

 

-On Location 

 

- Generators are usually your biggest offender. Asking them to move this on the day of shooting can be a huge deal. going on scouts for TV shows is usually out of the question so get the rigging gaffer on your side so 1.) there wont be a problem on the day and 2.) they dont have to move it.  if it is a problem on the day see if transportation  can park a truck in front of it.  or worst case scenario see if it can be moved without holding up production. if it is a serious problem do whatever it takes to get that thing moved.

 

- not much you can do about heads on outside locations  and I found that I am usually worried more about the other offenders like traffic wind and random yelling and talking dont forget footsteps.

 

- once you have tried all of this and you think you have done all you can without completely ruining your relationship with your lighting department. talk to post production (another VERY important relationship) over the next couple days. ask them if the noise was offensive or if they could fix it.. more times than not they will laugh and say oh that its fine we took care of that in seconds just keep the mic on axis LOL

 

fact is we usually dont have much time to address problems so do what you can and pick your battles wisely

[Simon Hayes]

^ GREAT POST

[AustinHunter]

black wrap on the lamp?

[RPSharman]

Pick your battles wisely is great advice.

It's very important to know what a light should sound like, and that only comes with experience. Experience also tells you what is a problem and what isn't.

For me, I don't want them to get too "casual" when things aren't a problem (exterior scene on radio mics with loud actors), because then they'll think it's ok the next time, when it's not ok (quiet interior scene on the boom). Bad habits are hard to break, so it's important for all of us to help each other by reinforcing the good habits discussed above.

I always thank the riggers when genny placement is clearly for my benefit and well thought out, etc.

Robert

[Simon Hayes]

Good point Robert,i make a point of thanking everyone involved for a good rig.

[Constantin]

On my current shoot I am not allowed to put the hmi's (if they are close to the set) off the flicker free setting. They are shooting with the Epic in HDR mode (I think that's the name) and they claim that's why it needs to be flicker free. Don't know if that's really true. Has anyone else experienced this?

But at any rate, I have found that these things don't really have a silent mode. Flicker free vs 50/60Hz only seems to affect the noise from the light itself (that high-pitchemd tone). This is fairly easy to remove in post anyway. The real problem is the fan noise (and whatever else they emit) at the other end, and the methods described here tend to work well for this.