As someone with disposable income working in an open office, I desperately want to know if this can be used to build something to cancel out human voices more completely than Bose QC-35s.
For voices you need passive sound isolation, not active noise cancelling. Try these: Howard Leight by Honeywell Sync Stereo MP3 Earmuff (1030110), Black https://www.amazon.com/dp/B004U4A5RU/
They also give off a very strong “I’m busy” vibe
If that’s still somehow not enough, wear these concurrently (this is great for planes too): Etymotic High-Fidelity Earplugs, ER20XS Standard Fit, 1 pair, Polybag Packaging https://www.amazon.com/dp/B00RM6Q9XW/
Also recommend the above with these foam tips for longer wear, I’ve done up to 16 hours with only a little discomfort: Shure EABKF1-10M Medium Foam Sleeves (10 Included/5 Pair) for E3c, E4c, E5c, E500PTH, i3c, i4c & SE Earphones (Black) https://www.amazon.com/dp/B0015PN3W6/
How about for lower frequencies: motorways, busy roads (no individual car noises; a solid background roar)? They make having the window open here a nightmare.
Not a fan of the QC-35. I find their ANC headache-inducing, and while the overall sound signature is very good, it's only because of built in DSP doing EQ. The distortion is unbearable.
Thus I use the audio-technica MSR7 at work. At home, I don't need isolation, so I enjoy sennheiser's HD600.
The trick with this material is that it pretty much reflects sound waves. On the way back, these reflected sound waves then crash into the upcoming soundwaves and they cancel each other out.
Headphones with active/acoustic noise cancelling use the same trick, except that they pick up the upcoming sound waves with a microphone and then use a speaker to generate those "reflected" soundwaves.
Actually-reflected soundwaves cannot be as strong as the upcoming soundwaves, so they're never going to fully cancel out the noise. Those generated soundwaves can.
One point is that there's most likely less latency for a soundwave to get reflected vs. picked up by a microphone and then generated by a speaker.
However, to my knowledge our human senses have even more latency than both of those, so I don't think that matters.
Don't extrapolate our slow reaction time to mean more than just that! :) Low latency still matters. Think about latency when scrolling/dragging on a touch screen for example. There's a large difference in feel depending on latency, even if the latency is lower than your reaction time.
This is a very bad meme that's been propagated so much across the internet.
1. The latency is active noise cancelling systems is very low; much less than the frequency of most sounds.
2. Noise cancelling is ineffective at higher frequencies because the space between the speaker driver and the ear becomes large enough that the destructive interference becomes imperfect.
3. The feedback has to come from somewhere, and once the frequencies become high enough, the phase shift caused by the physical distance between the driver and microphone start to affect the feedback loop.
4. Because of these issues at higher frequencies, they just lower the feedback gain at higher frequencies. This effectively makes the active noise cancellation system be not sensitive to higher frequencies.
5. This is very much akin to frequency compensation in other topics like buck converters and op amps--the additional phase shift in the feedforward path that often increases as frequency goes up becomes problematic to compensate, so they just make the feedback loop insensitive to that region.
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the quick way to debunk this is two tests:
1. Play some bandlimited noise (https://www.youtube.com/watch?v=5qV5j9wD5e8) really loudly and I guarantee you any shitty ANC headphone will cancel this out just fine. Noise by definition is non-repetitive.
2. Play a high frequency sinusoid (https://www.youtube.com/watch?v=TRKB5kWs7KE) really loudly and it will go straight through any ANC headphone. A sinusoid is as repetitive as it gets.
I've found that musician earplugs under ear defenders essentially cancels all sound, including human voice.
It's not something I would recommend. It makes me feel uneasy. A dozen people could walk up behind you and watch you work, and you'd never know until they tapped you on the shoulder. If you have any anxiety at all about this, true silence will make it far, far worse.
Noise isn't the only problem with open office layouts. It's just a convenient way to describe it to people who don't understand. If you think it's hard to talk to business people about the problems caused by excessive sound levels, imagine how difficult it is to talk to them about how you feel.
At some level, though, they do know this. Your CEO doesn't have his desk facing the door of his office because that position is the quietest. Try do-si-do'ing his desk one day and see how long that lasts.
Since you mention disposable income, if you can tolerate in-ear monitors I would suggest getting custom-fit silicone IEM. Used with even a very low level of music (or even some white noise generator) they dampen noise like nothing else in my experience. Successfully tested in a work environment with endless yammering, bleeping computer equipment, that mandatory 'shout-speaking' colleague, and even once a guy who let a 1U server running on his desk for a week for testing purposes (because why not).
The only down-side for me was that they are not as quick to pop on and off as regular headphones.
Careful with those Bluetooth headphones, a colleague of mine managed to pair her laptop with her speakers rather than her 'phones, and then promptly proceeded with listening to a (veee-eeery) adult audiobook.
Apparently, it can be quite difficult to determine whether the sound comes from your phones or outside them if you haven't turned the NC on.
