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Calibration tone

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Rodney M
Calibration tone
on Jun 7, 2007 at 11:47:40 pm

I thought I would share a little secret that I've used for the last couple of years, that some of you may already be using, but if not, this could be helpful. And that is, changing your calibration tone from 1kHz to 400Hz (or whatever is available on your mixer, if at all). I own the Sound Devices 442 which allows you to choose from 3 (I think) different tone frequencies. They come defaulted to generate 1kHz , which has to the most awful, annoying pure tone they could come up with. I think many of us in our pre-Sound Devices days have temporarily blasted our ears with 1k tone, not realizing our headphones were turned up as loud as they were (the 442, and I think the 302, automatically attenuates the headphone output level when tone is activated). 400Hz is much less piercing, even at higher volumes. So even if you're headphones are turned up too loud, you won't be throwing them off of your head because your eardrums are being assaulted.

Also, many cameras come with tone generators built in these days. So when the camera operator selects bars, the camera will automatically insert it's own tone if the audio inputs are selected to internal/front. This bit me on my first shoot with a Vari-cam (which I didn't know had this feature). We were in a hurry to get started and I handed my audio cables to the cameraman for him to connect from my mixer to the camera. He connected them but forgot to switch the inputs on the camera to rear. So I turned on my tone at the mixer and listened to the return from the camera and heard 1k tone, which was what my mixer was set for. I figured I was good to go. But when the interview started, I heard the front mic on the camera and realized there was a mistake. If you select 400Hz as the tone on your mixer, then you will know if you are connected to the camera correctly just by listening. If you hear 400Hz in the return, then the camera's inputs are set to rear. If you hear 1kHz, the camera is set to front.

I also learned to always, ALWAYS connect my audio to the camera myself - even if I am working with an experienced cameraman (which I was that day). Don't trust somebody to do it for you.

So, change that tone to 400Hz. Your ears will thank you and you might keep yourself from getting hosed when you least expect it.



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Ray Palmer
Re: Calibration tone
on Jun 8, 2007 at 2:22:30 pm

Rodney,
Thank you for taking the time to post this and for possibly making me look good in the future by knowing this ahead of time.

All the best.
Ray





Ray Palmer, Engineer
Salt River Project
Phoenix, AZ
602-236-8224 office
There are three types of people in this world, those that can count and those that can't.


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Stephen Muir
Re: Calibration tone
on Jun 8, 2007 at 2:51:38 pm

Good advice, thanks for the tips.

My PSC M4 mkII generates 600 Hz tone, and I've certainly found it to be easier on the ears.



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JC Boulay
Re: Calibration tone
on Jun 12, 2007 at 4:13:14 pm

Even though 400 and 600 Hz may be easier on the ears, they are not reference tones per se. The main level tone for any reference level is and always will be 1kHz. Other frequencies should be used to assure alignment along the whole frequency range between two system. Since the end of analog tape, the 20, 150, 400, 600Hz and 10 and 20 kHz tones see almost no use. They are still available on certain machines, though.

400 and 600 will be pretty damn close to 1kHz on the VUs anyhow, and this won't create any problems in practice, but any sound engineer getting your stuff down the line will not be super-impressed. Standards exist for a reason, and the 1k tone is one of them. Even if this all works in practice, don't be surprised if you hear back from a studio engineer wondering what the hell you were doing. I'd scratch my head for sure.

JC Boulay
Audio Z
Montreal, Canada
http://www.audioz.com


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Rodney M
Re: Calibration tone
on Jun 12, 2007 at 8:38:55 pm

Well, it's a good thing I'm not trying to impress anyone now is it?

I understand full well that 1kHz tone has always been the MAIN reference tone, but it certainly isn't the ONLY reference tone. There are some mixers available (Sound Technologies) that have 400 Hz tone as the default tone. As long as the said tone is 0dB (-20db digital) reference level, then I see no real problem using 400, 600 or 1000, unless that client has specified reference levels ahead of time (ie, 1kHz at 0dB, 400Hz at 8dB below reference, etc.). In the absence of analog tape machines that need multiple frequency alignment everytime you record, I see little point for your argument.

I've been using 400Hz for a couple of years and have heard no comments from anyone "down the line" which means that it works well enough to not cause any problems. Trust me, if there was a problem our clients would let me know - QUICKLY. I understand different tones exist for a reason, and though I don't propose to know it all (far from it), I do have a pretty good idea what works in a post house (I worked in one, as an audio mixer) - 400Hz has never been a problem.

Maybe you could point me to some resources that will convince me to not use 400Hz. If I'm wrong, I'll change my mixer back to 1kHz and will post an apology and the correct info. I certainly don't want to be guilty of propogating incorrect information and practices that are detrimental to our industry. I've worked too hard to make a name for myself as a competent audio engineer to let that happen.



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HowDoYouDoThat
Re: Calibration tone
on Jul 31, 2007 at 2:42:05 am

I apologize for jumping late.

But I couldn't let this one go.

First, why the heck are you listening to tone? Set it, check it, record it.

1K is the defacto standard for the industry. Has been for the 28 years I have been in the business.

Just because 400 is easier on the ears doesn't make it right.

Standards exist for a reason, to keep the work flow consistent across the industry. That way when I shoot a tape and uplink it to where ever or give it to an editor, they will ALWAYS set the tape to bars and 1K tone! (standards).

I'd be careful posting misinformation. Some new sound guy might listen. Then he'd look awfully dumb.
Good luck!



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