I'm sorry, but I can't figure out what you are doing.
1/ You can use a parabol with a OMNI mic connected to one stereo channel.
2/ you can have the SAME type of omni connected to the other stereo channel.
3/ you can connect the headphone output, so that one of the channels is
inverted, and the two channels into mono. (you will need 2 transformers
to do this, or electronics doing it)
4/ Now you can have the parabola on a tripod, and by random, move the outer
mic around until you get "best" noise reduction. This process cannot
be predicted or calculated, as you have no facts to base your prediction on.
5/ The frequency you will filter out, will be dependant on the wave length
vs. the distance between the mics. If the noise is broadband, you will
filter only a part of
it.
I don't know what happens if you try to do this with directional
microphones. It feels like you are going into a total chaos of parameters
which you can never get control over.
Using an outer mic for noise cancelling, is VERY experimental, only.
Klas.
At 00:50 2002-02-11 -0000, you wrote:
>Ok I tried this in cool edit. I took a Mono track, converted it to
>Stereo, inverted one track, and reconverted it to mono. Sure enough
>there was no signal left.
>
>Now I run a ME 67 long shotgun over my 32" dish. My original thought
>was to be able to aim my narrow 32" dish and cya when I overrun the
>preamp on a loud recording received by the dish. But I also see that
>I can pivot my shotgun because of the way I mounted it and will be
>able to point it at single source noise problems, invert and cancel.
>
>How far away can I have the diaphrams of the two mics before I can no
>longer use this technique? Is 24" to far?
>
>--- In Klas Strandberg <> wrote:
>> Using a mono parabol, you can have an extra omni outside of it and
>connect
>> it antiphase. By moving it, you can "tune" your filtering to the
>noise which
>> is present. The remaining noise is the noise which is reflected by
>the
>> parabol "only".
>>
>> Klas.
>>
>>
>>
>> At 14:21 2002-02-10 +0100, you wrote:
>> >> Date: Fri, 1 Feb 2002 09:39:46 EST
>> >> From:
>> >> Subject: Re: noise filtering 101
>> >>
>> >> Jeff,
>> >>
>> >> You audio sounds pretty good after being filtered. Here is a few
>things I do.
>> >> When I have recordings with car noise, I first use the FFT
>filter to do a
>> >> 85dB rumble cut for anything below 120Hz. That gets rid of wind
>noise too.
>> >> When I use noise reduction, I get the profile from the sample,
>manually
>> >> select a line just over the green noise signal, and reduce noise
>by 80dB. I
>> >> noticed your settings are at 40dB. I usually keep the noise
>reduction level
>> >> slider on the low side. Overdoing noise reduction ruins the
>quality of the
>> >> audio, so you might have to play around a little. Cool Edit Pro
>has a hiss
>> >> reduction plug-in that seems to work better than noise
>reduction. There are
>> >> other noise reduction programs available, such as Algorithmix
>> >> (http://www.algorithmix.com), that may work better than Cool
>Edit. I gave up
>> >> trying to get quality audio anywhere near highways, railroads,
>and airports,
>> >> but sometimes that is a luxury that can't be often found.
>> >>
>> >> The only thing you can do about faint recording is to either get
>closer to
>> >> your subject or get a preamp for your mic. For noisy
>environments, getting
>> >> close to your subject is critical for quality recordings. Did
>anyone ever
>> >> think of putting a mic with a long cable on a remote controlled,
>camouflaged
>> >> model boat? Sounds like it could work.
>> >>
>> >> Bruce
>> >>
>> >
>> >I experience a continuing growing problem with noise.
>> >Because of growing population there is always some kind of
>> >unwanted noise somewhere. You can name them all, plains,
>> >trains, highways, farmers with machines or a loud radio on
>> >some populair station. Is it the right way in using all
>> >kinds of systems afterwards? I experience the same problems
>> >with overdone or degrading the wanted sound too much by
>> >cutting too much. With computers today all kinds of
>> >unbelievable filters can be used. But with severe cutting
>> >you degrade the wanted sound often too much. I'm wondering
>> >if it might work when you use a hightech filter between the
>> >mic and the recorder or by using a shotgun with an out of
>> >phase random mic for noise canceling. I suppose its not an
>> >easy task because you have too set the equipment to a
>> >certain level so your ready for recording instantly. Whats
>> >your opinion about this?
>> >
>> > Joop Nijenhuis
>> >
>> >
>> >
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>> >
>> >
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