Can someone help me with a nyquist filter? ??

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Can someone help me with a nyquist filter? ??

Permanent link to this post Posted by rudolph172000 » Fri Nov 28, 2014 3:39 am

I'm not sure if this is the right place to ask this, or if I'm asking this properly - so I apologize if I'm too wordy


several people enter my home and experience severe ear discomfort. My uncle loses hearing aid reception when he comes in. at times, weird sounds are heard by those who visit. I experience odd radio sounds from time to time. Others notice nothing. I'm not sure if something is going on with my phone/cable/wifi or it's a satellite thing, etc.

but I'd like to get a better idea of what I'm working with. ...as it's become fairly prevalent.

I don't know a lot about audacity, but I got the zoom h5 and recorded the silence and uploaded my files back to audacity and put on spectrogram - - -


there is a full range of audio from 0 hz to about 10000 hz.

but the majority of my audio seems to peak between 20 hz and 120 hz. -- when I try to play back I can see that there is activity, but no sound. When I amplify loud enough to hear, it's too clouded by noise to make out what I'm hearing.


Can someone make me a nyquist filter that will make these frequencies loud enough to hear, and cut out the outside noise
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Re: Can someone help me with a nyquist filter? ??

Permanent link to this post Posted by steve » Fri Nov 28, 2014 3:48 am

rudolph172000 wrote:Can someone make me a nyquist filter that will make these frequencies loud enough to hear, and cut out the outside noise

No need, the filter is already included in Audacity. Look below the divider in the Effect menu for "Low Pass Filter".
Try setting it to 48 dB per octave, 150 Hz. Apply the same filter twice (Ctrl+R to repeat the last effect). That will take out almost all sound above about 180 Hz.
Then apply the Amplify effect (default settings) to boost the signal back up to full scale.
You'll need some big speakers to hear sound below 50 hz. Small / medium size speakers will just rattle.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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Re: Can someone help me with a nyquist filter? ??

Permanent link to this post Posted by kozikowski » Fri Nov 28, 2014 7:22 am

several people enter my home and experience severe ear discomfort. My uncle loses hearing aid reception when he comes in. at times, weird sounds are heard by those who visit.

None of those are caused by low frequency sound. Those are all high frequency effects. Ultra-sonic tones will give you a headache and overload hearing aids. The third symptom may be young people that can actually hear the tones. Does the effect break down that way — do young girls (terrific hearing) complain about weird sounds?

"Mum?? What's that screaming sound?" [just before starting to cry]

Do you have a dog or cat? I bet you don't.

You can probably attack this with technology, but I'd find one of those people who can hear it and start turning off electronics and electrical services in your house or apartment. I got as far as completely shutting down my property once to prove that the neighbor was generating interference.

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