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Topic: Antidote To Subwoofer Noise Nuiscence (Read 832 times) previous topic - next topic
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Antidote To Subwoofer Noise Nuiscence

I am having problems with a neighbor playing low volume drumming music in garden which can be for up to 8 hours  whenever we have a sunny day. Complained to local council plus Environmental Health but they won't help so may have to move.

Whilst I was reading upon noise cancelling headphones using frequency inversion, I wondered if same theory could provide a solution for me, noting that it can be used on a larger scale for industrial noise etc.

Plan A: Initially I thought of using a microphone, amp and sub woofer to replay the drumming noise inverted, thus cancelling it out (providing of course that there is equipment available to invert the source audio).

Plan B: Then I read another article about stereo speaker being out of phase causing the resultant audio level to be very much reduced. Maybe if I just replayed the drumming noise through a standard amp & subwoofer but tweaked the speaker polarity so it was out of phase with the source one hopefully cancelling it out.

Either of the above would be preferable to moving house but would appreciate any expert feedback before I start experimenting thanks.


Re: Antidote To Subwoofer Noise Nuiscence

Reply #1
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Plan A: Initially I thought of using a microphone, amp and sub woofer to replay the drumming noise inverted, thus cancelling it out
In the real world that won't work.  :(  You need the exact-same volume, exactly inverted.   It could  work to some extent if you could put a microphone near the offending noise, and if you didn't move once you get the sound waves cancelling.

It works with headphones because the microphone is close to your ear but outside of the headphone so it can pick-up external noise (exactly what you ear would hear) without picking-up the "cancellation sound" from the speaker inside the headphone.

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(providing of course that there is equipment available to invert the source audio).
That part is easy!    You can just reverse the connections to the speaker. ;)  (Or, it can be done electronically or digitally.)

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Plan B: Then I read another article about stereo speaker being out of phase causing the resultant audio level to be very much reduced.
If you reverse the connections to one stereo speaker the bass will be almost completely canceled.    Plus  you'll get a "spacey" "stereo widening" effect as the other frequencies (shorter wavelengths) bounce-around the room combining in and out of phase, depending on the room acoustics and where you are in the room.  

...If you just play a regular (in-phase) high-frequency stereo test tone, the distance between your ears means there's a phase difference between the left & right speakers and slight movements of your head will make drastic volume changes as the left & right (and reflected) soundwaves go in-and-out of phase.   i.e. 10kHz has a wavelength of about 1.3 inches (3.3cm) so half that difference is 180 degrees. 


Re: Antidote To Subwoofer Noise Nuiscence

Reply #2
If you limit your effort to, say, <200 Hz, then:
1. Timing is a lot less critical (at 48kHz sampling, you can "do stuff" for many samples and still be at a similar phase of a 200Hz sine)
2. Placement is a lot less critical (a low frequency signal entering your apartement and another stemming from your subwoofer) will be out of phase for a lot larger area at 200Hz than at 10kHz).

That being said, my hunch is that you will end up with an interesting hobby project, but probably not something you would actually use outside of novelty.

At low frequencies, rooms tends to be "modal". I am not sure how you would go about creating the desired acoustic waveform using your subwoofer without room reflections messing that up.

Have you tried active noise cancellation headphones?

-k

Re: Antidote To Subwoofer Noise Nuiscence

Reply #3
Just sue them, you may not even need a lawyer. www.nolo.com
Quis custodiet ipsos custodes?  ;~)

 

Re: Antidote To Subwoofer Noise Nuiscence

Reply #4
Bag End actually makes one of these called the E-Trap. It's designed as an active bass trap for correcting room acoustics. I don't think it's been updated in quite sometime as all the circuitry appears to be analog. In any case, it would be useless for your application because it would only work when the bass trap was on axis with you and the drummer (preferably between).

 
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