I bought a $30 set a while back just to check them out. They seemed only to add a light layer of “white noise” - I could still hear background noise. More recently, however, I asked a fellow passenger on a roaring loud plane if I could try theirs - and it was amazing how the roar disappeared with a click of the switch. What gives? Do the more expensive models (an assumption, as the borrowed pair was from someone in business class) really work? And if so, how?
Well, you need a good microphone (two, actually) for a noise-cancelling headphone to work, and they cost money. $30 is dirt cheap even for a normal pair of headphones.
The electronics of the unit are also crucial and will determine if all you hear is an added noise or actually the phase-inverted outside noise. The effect of the noise cancellation depends on the type of background noise. Airplane noise is very uniform, doesn’t have many transients and is usually situated in a low frequency band, all of which makes it easier to be masked. The physical effects of well-insulating headphones are another factor - more expensive phones will cover your ears better, which makes for a better attenuation even without the electronics. The list goes on, but you get the idea?
FYI, this is how noise cancelling headphones work. They contain one or more microphones that pick up the noise around the user’s head. The rebroadcast that sound through the headphones. ideally 180 degrees “out of phase” with the original ambient sound. Sound waves are additive, so if one wave is generated at the same moment as another, opposite one, they will add up to a net zero and no sound will reach your ears.
There are a lot of places where this scheme can fail. First, the first wave can’t be entirely cancelled, because it takes time to analyse and generate a counter-wave. For pretty much the same reason, sudden and non-repetitive sounds can’t be entirely suppressed. The system works best in situations with background noises characterized by a steady drone or hiss, since as the waves repeat the earlier ones can be used to continually generate the waves that cancel out the later ones.
I can’t tell you why your set failed. Possibilities – Crappy microphone that doesn’t get a true reading of the exterior noise. Crappy little speakers that don’t accurately reproduce the waves picked up by the mic. Crappy processor that doesn’t properly reverse the phase, or feeds it to the speakers with bad timing so the waves don’t fully cancel each other out. Or – some combination of these things.
I have a pair of Bose QuietComfort 3 headphones, and they do a great job of diminishing background noise, especially on a plane. I say “diminishing” rather than “blocking,” because for example, if someone is speaking to you, you can still hear their voice somewhat, but sometimes not enough to tell what they’re saying.
I’ve never seen a $30 pair of noise-canceling headphones. I have seen cheap noise-reducing headphones, most often as in-ear buds which simply block noise the way earplugs would. There’s no way you can put enough effective electronics in a $30 pair of 'phones to make anything like worthwhile noise-canceling headphones.
Often the cheap headphones will say they have passive, rather than active, noise canceling. All that means is the foam blocks some of the outside noise from getting to your ears.
sure you can. The circuitry for a $30 set and a $1000 set is going to be a computer chip and a few miscellaneous off-the-shelf electronic components. the cost to make that is going to be the same. You’d be hard pressed to justify the difference in the cost of materials (gel earpads, head band, microphone, speaker, etc…). Yes there will be a difference in the latest design specs but the production costs will be minimally different.
Not to undermine the actual differences between a $30 set and a $1000 set but the the basic components are the same minus the most recent chipset. I’ve updated the guts of my aviation headset to make them noise cancelling and there isn’t much to it.
I am skeptical about what you posted. Years ago I owned stock in a company [that I think was called] Noise Cancellation Technologies. They were working on the science of noise cancellation and seemed to have a real future in the time when tech stocks were high flyers. The stock tanked and I dumped it and then lost track of them. I think the company and it’s patents got sold. Maybe Bose picked them up but I don’t know.
It’s entirely possible that the $30 headphones were just introducing white noise and the expensive headphones have state of the art, patented, noise cancelling ability. The technology is more than just a computer chip. Some pilots use noise cancellation headphones that are very expensive. They are not just glorified $30 headphones.
To start with the op talked about noise canceling headsets from the mindset that they eliminated noise in general when that is not their function or within the realm of their function. As has been pointed out, they are capable of eliminating cyclical noise such as the drone of an aircraft engine.
While I admit there is a difference between a $400 headset and a $1000 headset it’s not a component issue. They all do basically the same thing. Aviation headsets are a low volume commodity with lots of competition. Bose is at the top end of the price scale and I stand by my assertion that while they may be marginally better than the lower cost units the difference in price is not a function of the cost of the internal components.
When you open them up they’re all basically the same, microphones, speakers and a little bit of electronics. My little 23" inch LCD TV is exponentially (by many many multiples) more complex than a Bose headset yet is a fraction of the cost.
I’ll add that your investment was a modern example of the ability of countries like China to swoop in and reverse engineer new technologies. Sound cancelling technology is, IMO, almost a purely intellectual technology. It is applied software that is easily deconstructed and reinvented in a patentable way.
I too would have invested in it given it’s original application possibilities but I lacked the funds to do so. I thought it had tremendous potential by eliminating noise from trains and other noisy industrial equipment.
The problem is, it only works with headphones. There may be some very narrow fields of application without, but you’re just not going to get the soundwaves aligned unless you put both the microphone and the speaker within an inch of your ear. You would take one step to the left, and the wave that was out of phase a second ago is now perfectly aligned and therefore even louder than before. While the idea of silencing trains sounds very appealing, it’s not physically possible.
The world is moving on. Researchers in Cambridge have produced a system that uses phased-array steerable speakers to focus a stereoscopic sound image on the ears of a listener identified using a video camera (or, more probably, a Kinect sensor). A personal 3D soundfield, if you like. And they can do this for (currently) up to 8 people at once. The concept of using this sort of technology to cancel the noise of a train in a particular space (like a station platform, or a room in a nearby house) is getting much closer.
And the cost of high quality active noise-cancellation equipment is falling, as more powerful general-purpose CPUs (cheap in volume) take over the job, as compared with custom Digital Signal Processors used in earlier systems.
Si
Obviously I can’t really say anything without looking at their research, but the problem is the wavelength of sounds. At 5 kHz, wavelength is less than 3 inches, so if you as much as turn your head, you get a full addition instead of the desired cancellation. This, of course, is different for every single frequency. I’m not sure those systems work that accurately. Lower frequencies up to maybe 100Hz or so might be more feasible. So while I’m sure that research in that field is being done, I won’t hold my breath.
No, it’s not restricted to headphones. When I first heard about the technology they talked about applying it directly to the source. GM is apparently doing it with a carbut this article doesn’t state how.
Wikiarticle talks about the technology applied directly to the source.
"Antinoise is used to reduce noise at the working environment with ear plugs. Bigger noise cancellation systems are used for ship engines or tunnels. An engine’s cyclic nature makes FFT analysis and the noise canceling easier to apply.
The application of active noise reduction produced by engines has various benefits:
The operation of the engines is more convenient for personnel.
Noise reduction eliminates vibrations that cause material wearout and increased fuel consumption.
Quieting of submarines"
duplicate post
I have a piggy-back question on this:
When I wear my noise canceling headphones, does the sound that is canceled have any effect on my hearing? In other words, is the next effect of the additive sound that there is no sound, or is it just that I can’t hear it. I suspect it’s the first but wanted to be sure.