Anyone here have experience using active noise cancellation to soundproof a home/room? The idea would be to utilize an outdoor or indoor microphone to read low frequencies, and broadcast the inverse into the room using a speaker, thereby cancelling the noise.
I don't believe that the low frequencies are what we associate with "noise".
Noise usually occupies a wide band on the frequency spectrum, but it's the lowest frequencies that have the easiest time entering our homes. And they are also the hardest to block. Engine noise, motorcycles, lawnmowers, airplanes, etc. The higher frequencies get blocked easily by walls and windows.
Lower frequencies are higher energy. Eliminating them with noise cancellation would take an equal amount of energy with an inverted phase. Eliminating them with sound blocking material(s) is probably a better choice.
Not always possible, even with the best intentions. For someone like me, who has gone through the trouble of blowing additional insulation behind my drywall, and applied extensive room treatment in the form of bass traps and other sound absorbing material, it still fails to block the lowest frequencies. The next step is the "nuclear option" of tearing it all down and building a room-within-a-room. Very expensive and time consuming.
Some startups are trying to tackle whole home active noise cancelling but it's still in its infancy. Some cars have had active noise cancelling for years now. The idea is that active home noise cancelling would mostly address the hardest to tackle frequencies, the lowest ones.
Though the sound pressure is higher for low frequencies outside, it's much quieter indoors and wouldn't take a lot of volume, with an appropriately sized subwoofer for instance.
Here's one such company:
Practically impossible to do outside a narrow listening 'zone' because it comes from all directions, bouncing off all kinds of surfaces.
That's why it works best with headphones, as the headphone mic picks up the incoming sound directly at your ear and generates the inverse amplitude at that same spot. Same principle for cars (as you don't generally move much beyond the seat position). Imagine a system trying to track your position through 3D space (and that's only for 1 person, then imagine what it might take for 2, 3, 4 .... people).
If you are taking about a music listening room then it would be feasible to soundproof a singe chair, However it probably would be counterproductive as the ANC would also interfere with the music.
Ultimately, I wouldn't say it was completely impossible, it's probably doable (but only to an extent) with a massive mic array, motion trackers and computer power.
Yes, I think below a certain frequency it might not work because the wavelength of a particular frequency would be long enough to result in the locational issues you describe. For instance, a 100hz tone has a wavelength of about 11.3ish feet, which would be easy to be in the wrong place in a smaller room.
However, higher frequencies might work out better here. You'd have to move extremely fast to outrun the inverse wavelength of a 10,000hz frequency... or... or perhaps it would be nearly impossible to match up an inverse 10Khz wave with itself in a large space.
Seems experimentation is necessary...
It's not about "outrunning" the frequency. You have to measure the precise mix of audio signals and frequencies at the location you are standing at (at your ear preferably) and then generate the inverse amplitude of the sounds in order to arrive at your ear at the same time in real time. This is a non trivial exercise and that's why it's limited to the narrow range of applications that the system you link to is capable of fulfilling. This is a problem that has not been solvable (at least in a commercial setting) for decades AFAIK.
Much easier to passively soundproof your room TBH.
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