How can one keep from overloading a camcorder mic
 

I'm using two camcorders mounted inside the cabin of Late Model race cars. The video's great but the environment is so loud it simply overpowers the onboard microphones.

The worst is an old Sony TRV-19. The noise level is so high that it overloads the audio inputs and the audio will periodically cut out. The other is a Panny PV-GS400 which has a menu function where you can set the audio down -30dB and have a limiter on. Even with the volume all the way down it's overloaded. Not hard to do when it's that loud. Doesn't cut out but it's definitely distorting.

I was wondering if there's something you can put over the microphone opening, like tape that would help muffle the sound and not make the audio section run for the exit. Or, would it not help since sound that loud could sneak into the mic area straight through the casing.

Suggestions anyone?

A lot of older camcorders have a small "external mic" jack.

I took a look on-line and the TR-19 and the GS-400 specs both show a mic input.

You can sometimes just put a dummy plug (unwired 1/8" male plug) into that jack and it will cut off the mic circuit.

Worth a try since it's cheap.

Hi Tripp...........
 

A layer or two of pleated rubber carpet underlay should provide a bit of grace.

Won't look Hollywood but sure helps kill the sound.


CS

Hi Chris...
 

Are you on a mission to become my personal mentor? Regardless, I appreciate your help.

I'll give that a go. I don't really care what it looks like. Both the cameras are festooned with bits of tape covering various controls so that someone doesn't inadvertently bump one so a little underlayment will hardly make a difference in how silly it looks.

Bill... I don't want to cut off the audio, just attenuate the volume. I was thinking about using some small external mics and putting a pad in-line to step down the level, but I'm guessing that the intense volume could overwhelm most standard microphone diaphrams.

Yeah, in an environment like that, you're going to have a hard time not overloading your mics. If you use an external, you'll want a dynamic mic that can handle exteremly high SPLs. I'd recommend a mic designed for use on brass or close-micing on a drum kit. The very popular Shure SM-57 might work for you without getting blown out. And you can get an XLR-mini plug adapter. Since its a dynamic mic it won't need phantom power.

Trip,

I don't think it's just a volume issue, but more probably the significant amounts of mechanical vibration you'll be facing. Bolting camcorders and their fixed microphones onto the cage rails will STILL transfer a whole lot of that to the physical mic housing, so I'm not sure that even if you attenuate things properly you'll get great sound. Not when the actual mike armature gap will be shaking around all over hell and back.

I'd also expect tape/heads contact issues, but that's another subject for another time.

In all the auto racing coverage I've seen, particularly with the modern wireless cameras, the "in car" audio is typically just the drivers comm channel overlaid with the track ambience mics. I've never actually heard "in car" audio - and I've always chalked that up to this problem with physical shaking.

But by all means, try it and see what a padded signal sounds like. You might strike gold.

Let us know how things turn out.

Bill... I have no illusions that I'm going to get any sweet audio in car, although it can happen. The networks do get good in-car audio but it's an art form and there's a whole team needed to get it done and I'm a team of, well, one.

Curious that you mention vibration. The TRV-19 would get some video artifacts but the picture was rock steady. Rock steady that is right until the driver got helped into the fence. Tough night for a great guy who was really running well. The picture broke up a bit when he hit the wall hard enough to rip off the rear clip. Kinda suspected that the tape/head contact was compromised. Either that or there's something a bit lose inside.

The GS-400 had no such artifact problems in spite of the fact that it was mounted too far forward on the platform and would cantilever up and down a bit and the sound didn't break up at all.

Clearly it's a harsh environment and there are specialized systems to protect the gear. And I thought shooting on 30 foot racing sailboats was tough.

David... I have a Senheiser dynamic that's worth more than the Sony. Not sure I want to put it in harm's way, especially since I really need a good mounting system that will insulate and protect the mic.

Trip,

One suggestion, you might want to invest in a couple of those really cheap Radio Shack lav mics and try them plugged into the camcorder's mic input.

I'd suspect that gaffer taping them to the headliner somewhere would allow the mic element to "float" and decouple a lot of the mechanical noise from the process.

Just a thought.

Have fun, and remember your ear protection around race cars!

Is it worth $150 to you? That will get you a Senn SM57, an AT8202 in line attenuator and an XLR to mini plug adapter. The SM57 and SM58 are famous for their durability as well as their sound...what Senn dynamic do you have that you worry about knocking around? Anyway, a block of foam from a crafts store, a box cutter and some duct tape are all you need to minimize vibration and protect the mic's body if that's a concern.

That's a thought and would provide a way to muffle the mic without the sound leaking in around the camcorder's case and killing the onboard mic.

Taping the mic baffle to something, like the camcorder, would provide additional insulation against mechanical noise that is probably being transmitted through the camera mount.

If almost a decade of working in radio playing loud rock and roll didn't kill my ears... but I'm older now. I'm almost always wearing over-ear cans when in the pits and recording the races. Not sure it'll help tho since I've been accused of having audioanalitis. (Head so far up butt I can't hear for s#!&)

David... at this point, no. The Shure SM57/8 are extremely durable. I started using them back in the 70s and you can literally do everything but shoot them and they'll still work.

The Sennheiser is an MD46. It ends up in shots so I don't want it looking like it's beat to death.

One car that carried one cam last Saturday hit the wall so hard it caused the cam mount to shift, and the mount was VERY secure. A mike with the mass of a SM57 could break loose from anything but a secure mount and fly around the car or out the window. It might even hit the driver which is out of the question. I think an external lav mic might make more sense, but anything particularly expensive would endanger the profitability prospects of this project.

Your thought's a good one, but I don't think I can make it work in this situation.

FWIW, physics says...
A 284 gram SM57 secured in the direction of travel with three turns of 2" 3M high performance duct tape (tensile strength 36 lb./in) around its center of mass would stay put in car hitting a cement wall head on at 150 mph (67 m/s), assuming the duration of the crash was about 0.02 seconds, which would be the case if the front end were bashed in about 2 feet. Foam between the mic and the tape would reduce the impulse and allow a higher speed. So, if you had a structural member you trust (sufficiently rounded to prevent stress concentration) and you have enough clearance to wrap tape around it ...

...clearly, I have too much time on my hands 8>]