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Re: noise cancelling

Subject: Re: noise cancelling
From: Lang Elliott <>
Date: Mon, 11 Feb 2002 12:57:11 -0500
Klas:

I use a monaural Telinga with an MKH 20 mike. So all I'm doing is using a
Y-connector to add an additional mike (in this case another MKH 20 omni) to
the input of the tape recorder. I'm also re-wiring the XLR cable to this
omni in order to reverse the phase. I can then move the second omni around,
placing it within the reflector, along it's edge, or wherever to get the
optimal noise reduction.

Lang

> 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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>>>> 
>>>> 
>>>> 
>>> This outgoing e-mail is scanned for viruses with Norton 2002
>>> 
>>> Telinga Microphones, Botarbo,
>>> S-748 96 Tobo, Sweden.
>>> Phone & fax int + 295 310 01
>>> email: 
>>> 
>> 
>> 
>> 
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>> 
> This outgoing e-mail is scanned for viruses with Norton 2002
> 
> Telinga Microphones, Botarbo,
> S-748 96 Tobo, Sweden.
> Phone & fax int + 295 310 01
> email: 
> 
> 
> 
> 
> To unsubscribe from this group, send an email to:
> 
> 
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> 
> 
> 



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