If you fly much or work in a loud office, you know that noise-canceling headphones can be a sanity saver. Wouldn’t it be nice if you could just have noise-canceling without the headphones? Apparently, a lot of people think that’s a good idea and funded a project called Muzo. [Electroboom] borrowed one and — mystified how such a device could work — set out to test it. Along the way, in the video below, you can see him do a neat demonstration with two speakers canceling each other in his closet.
Based on [Electroboom’s] tests and the tests from other users, it doesn’t appear that Muzo does much to reduce noise. It might add some noise of its own, but that’s a far cry from what people expected the unit to do.
In theory, the device senses vibrations in a flat surface like a piece of glass or a table top and then vibrates the surface to oppose the noise. At least, that’s one of its modes. It is also supposed to be able to mask sound you make, creating a sort of privacy bubble around the device. It can also generate sleep noises, which — of course — might mask other noise, but won’t cancel it.
While it is a great idea, it is hard to imagine how a device like this could arbitrarily cancel complex sounds for all listeners with just a single device located some distance away. With headphones, the sound beams right into your ears and there is a lot of passive noise blocking, as well. There are other special cases where “in air” noise canceling can work
If you want to stick to headphones, you can get good results passively. Amazon, by the way, has an interesting patent filing related to noise cancellation.
Electroboom! He’s awesome. His videos are like science class for adults, not the evil teacher that made you hate your favourite subject. The cool one that told you not to play with asbestos, and let everyone hold dinosaur poop, and electrocuted the whole class with an old telephone dynamo. :)
inb4 full bridge rectifier
I think less of people who use the term electrocute for non death causing electric shocks.
My woodworking teacher zapped the whole class using the spark plug on an an old washing machine engine. It was quite hilarious to see everyone scream at the exact same time.
Too bad every one of his videos is an advertisement for something now. I understand he has to make a buck, but it’s not subtle.
I guess I’m the Munroe lackey now.
xkcd 368
This technology is the McGuffin for a Left Behind parody story that I wrote a while ago.
http://emlia.org/pmwiki/pub/web/VeryDifferentPlaces.VeryDifferentPlaces.html
It reminds me of the Fenton Silencer from Arthur C. Clarke’s “Tales of the White Hart”.
Sounds vaguely familiar…
If I remember correctly, the device was placed in a theatre or some such venue with the expected results. Except for the bit at the end where it exploded violently when the protagonist went to retrieve it as he’d forgotten to consider just where all that lovverly sound energy would end up.
Mind you, I could be mistaken. It’s been a very long time since I read those and I’m too bone idle to try looking it up :)
Tried. Couldn’t get it to work, processing too slow, not even enough performance to block noise through a single window and made noise of it’s own. Inspired by Sony having some success along those lines, though just in ductwork. I gave up, turned the equipment around the other way, had enough processing to phase the speakers and stayed in bass, 3 point cal good enough for array out in the yard, could “pet” squirrels and cats. Good laugh at first but they caught on fast and wife gave “that glare!”. Hauled all the speakers back to goodwill.
I’ll just leave this here.
https://www.youtube.com/watch?v=0cVlTeIATBs
Exactly 50 percent of people hooking up two speakers without paying attention do this all the time. in phase or not!
When I go to a show and the PA is out of phase that’s when I leave with my money.
Seriously when someone gave me a pair of those phones I checked them out without music, wow less ambient noise! Then it hit me, that one little AAA cell powered amplifier will not have as much power and probably quality as the smartphone I play thru them. So I loose power in the music vs. my phone yet alone a board or PA monitoring audition situation.
Most importantly it takes as much power at the frequencies around 20 to 200/500 Hz to drive the phones as the loudest noise that is to be canceled. You can not cancel loud rumble with a pair of tinny tiny phones. I give these frequencies as active noise canceling is very difficult at higher ranges because wavelength comes into play. Fortunately passive protection works well at higher ranges. Flat response across the noise band is necessary to ensure even canceling, otherwise cheap phones or speakers will be rough even louder at some frequency ranges.
Noise cancelling headphones are not regularly powered by an AAA cell. It’s more common for them to be bluetooth and so include a lithium ion battery. My phone does not include a headphone jack and even previous ones that have have had poor quality audio (it’s hard to jam a good amp alongside a noisy CPU). Noise cancelling headphones commonly offer some passive isolation reducing the volume of anti-noise required to cancel noise from outside. Noise cancelling headphones commonly feature a circumaural design allowing for drivers that’re 40 or 50mm in size, this means they’re effective at cancelling low frequency sounds, more so than high range ones.
Try a better pair of NC headphones, something like the Bose QC35s, though they do sound a bit naff without power so don’t consider them to be the last word in NC.
My headphones will never have blurtooth or need a power source of any kind. I have high def files on my phone no MP3’s. I feel sorrow for your loss of hearing with that arrangement. CPU noise, that’s in any digital device. Good design can make a line level audio amp in a phone, just don’t ask for AM radio.
Ironically compression and MP3’s increase the noise level in your audio at the loud end of things. If worried about noise exposure, filter a lot of treble out of what you listen to after blurtooth transmission.
Yeah…you seem like a lot of fun.
> Then it hit me, that one little AAA cell powered amplifier will not have as much power and probably quality as the smartphone I play thru them.
It depends on manufacturer, but that amplifier CAN have more power than your phone. Quality can be high enough too, unless you go for cheapest cancelling headphones. Good ones will be over $100-200, but even those high-end ones sometimes have bad quality sound. I have audio-technica ATH-ANC33iS and they sound better than “raw” in-ear headphones when powered (but I won’t call them high quality).
There are noise cancelling systems used in open plan offices already. They require speakers to be placed in the ceiling at certain intervals with a corresponding microphone. The speaker then plays back the anti-phase of the microphone to cancel the sound. I saw a demo system for propeller aircraft at Southampton university some years ago that used this system too to cancel engine noise in the cabin, at the time I was told it was only suitable for propeller planes and not jets. The waveforms produced by a jet aircraft were apparently to complex for this type of system to work properly.
Snake oil? Wavelength of 4KHz sound is less than 10cm. You need the microphone within a fraction of that in order to cancel, so 1cm from the ear would be OK but not great. The system simply can’t cancel for two people with one microphone. In fact, it can’t cancel for one person with one microphone.
If you know where the sound comes from and how it propagates, can you lower noise in a plane cabin? Yes, if the cabin is not too big and the sound is very low frequency, on the order of the cabin size being 1/4 wavelength or so, meaning less than 60Hz. Propeller speeds are in the 20 to 40Hz range.
I’m just reporting what I saw 10 years ago, it wasn’t my research. It seems to have worked good enough though as many propeller aircraft now use active noise cancelling systems.
this link provides some information on the work they were doing:
https://cdn.southampton.ac.uk/assets/imported/transforms/content-block/UsefulDownloads_Download/AF0ACA41AA0B43BDA83AF2C8643EC62B/Read%20more%20about%20identification%20and%20active%20control%20of%20multiple%20sources%20of%20sound.pdf#_ga=2.86805656.188433409.1511873165-2031999437.1511873165
or if you can access research papers this might be informative too:
https://www.sciencedirect.com/science/article/pii/S0022460X96900784
https://www.sciencedirect.com/science/article/pii/0022460X90905244
Can it beat the cone?
http://www.perreaux.com/images/dmImage/StandardImage/Get%20Smart%20Cone%20of%20Silence.jpg
Haha love that :)
That would be so trivial with one more dimension.
Thanks, I would like to build the experiment for students. What app should I download?