audio hum

Y

Yates

New member
I have a dvx100a that I've barely used but owned for years now. I've just discovered it records a slight hum or buzz at the 15750 frequency. It's subtle enough that I haven't noticed it until now. It's there on the internal mics and if I plug an external in. It's there if I record directly to a computer bypassing tape. It's also on tapes I recorded when I first got it.

Has anyone else seen this problem? Is there somewhere I can download other people's DVX-recorded raw samples (not youtube or edited material)? Like I said it's subtle, and I'm wondering if it just might be normal for this camera. Is there a good fix-it place in NYC if I decide to go that route?

Thank you
 
Couple of questions .. how did you determine it's 15.750 Hz. That's almost 16 thousand herz, it's very high in the audio range and wouldn't be classed as slight hum or buzz, it'd be a kind of high pitched whistle and low level.

It'd be too high and out of the range of a DV tape recorded on a DVX100A. What are you hearing it with, speakers, headphones? Most of those will have trouble reproducing that frequency.

I'd take your DVX across town to B&H NY, they're a sponsor here and always very helpful.

Cheers.
 
Thanks for responding. I can't hear it, which is why I haven't noticed it until now. So why do I care? Having worn out old man ears I am concerned someone else with better ears might hear it and be bothered by it. I can see it quite easily on a frequency spectrum display.

It'd be too high and out of the range of a DV tape recorded on a DVX100A.
Click to expand...

Don't they record at 48kz? That would be able to play 24kz accurately, wouldn't it?

I didn't know B&H did repairs. I might have to check that out if I decide to have it looked at.
 
You're right, a DV tape records 48kHz, which allows up to 24kHz of real audio, as it were. It's no coincidence that 15750 is 525 (number of scanning lines) multiplied by 30 (your frame rate - I assume you are NTSC). Dogs, small children, and teenagers who don't go clubbing every week will be able to hear it. My son used to be able to hear it until he reached about 18. I doubt that it's a fault with your camera. I'll take a look at the audio off my 100B and check if I can see it - if I can then it's probably there for everyone.

EDIT: Just checked and I get the same thing, with both internal and external mics. I don't think it's a camera fault.
 
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If it's just noise and you want to be rid of it, you could probably filter something like that out using a narrow-band EQ, or possibly a low pass filter.
 
Not sure what you use to edit your audio, however, taking a look at SoundSoap Pro 2 might be something worth considering. It remove hums, clicks and all types of noise from your audio. From my experience, hums aren't really an issue for this software. It's not too hard to learn since it's very straight to the point; you might have to fiddle with it 2 or 3 times but after that it can be a life saver in most cases. It's around $350 - $400 but it will pay for itself, especially if you can avoid taking your camera to get fixed.

http://www.bias-inc.com/products/soundSoapPro2/

-B
 
If you want to remove it you need a notch filter (essentially a very narrow band EQ) where you can specify a precise frequency. Depending on which video editing software you have, you may already have a notch filter. I suggest don't use a low-pass filter - even though you're removing frequencies you can't "hear" you'll do audible damage to your audio (because harmonics that you can't hear have an impact on those that you can).

But to be honest, if you can't hear the TV whistle, don't remove it.
 
Thank you for the responses. It's good to know the camera is working the way it should. Although, strangely, I think channel 2 is a little worse than channel 1 on mine. I am using Soundtrack Pro right now to remove it from a project I'm working on. It has a tool to select exact frequencies in the spectrum display and delete them. But maybe I should leave it. I guess I'll try to not worry so much about it in the future.
 
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