Tell me about Noise-Cancelling Headphones

[adk]

I'm not looking for recommendations, but I'm wondering more how they work. I understand that they generate frequencies opposite to the ambient noise, but does that mean that these sounds wouldn't hit my eardrum, or would both the noise and the cancelling-out noise hit my eardrum? Basically what I'm wondering is whether the noise disappears or if it is doubled but just becomes inaudible to me?

 

[yg17]

I'm not looking for recommendations, but I'm wondering more how they work. I understand that they generate frequencies opposite to the ambient noise, but does that mean that these sounds wouldn't hit my eardrum, or would both the noise and the cancelling-out noise hit my eardrum? Basically what I'm wondering is whether the noise disappears or if it is doubled but just becomes inaudible to me?

I think it's a combination of both. Most of them are pretty big and surround your ear to block out the sound, and then the opposite frequencies are generated to cancel out whatever gets through.

 

[Victor ch]

I have a pair of Bose's QC2 headphones that I absolutely adore. They work monitoring the surrounding sounds (they have a mic in each ear-cup) and digitally process it, sending and opposing frequency thus canceling the sound. I found they work fantastically well with low rumbles e.g engines, air conditioning rumble and almost every low frequency sound. They won't cancel the voices or high pitched sounds with just the cancellation circuitry on, but if you combine the noise-canceling plus the music trust me you won't hear a thing. They use what is called "active noise-canceling" and mildly include passive cancelation due to their cirum-aural nature, the "active" does require additional power usually from AAA batteries. Others use preset frequencies to cancel the sound giving worse results whilst the Bose have mics that monitor outside sounds. The "hiss" is very faint and you can tell when it is amplified if you do some sound as they will produce an opposite reaction. When you first use them you will feel this weird "pressure" that is mostly psychoacoustic since your not used to it, after a few hours of use you will stop noticing it. They will make low rumbles and things they can cancel without music completely inaudible and I do not what you mean by hitting your eardrum. I can tell you they work as I have made my dad go berserk a couple of times when he asks me for some favor and Im drooling away in my music unable to hear him.

As for the music quality, they surprised me. It is common for Bose products to be excessive in bass and poor in the highs; this ones are not. They have a very deep yet well controlled bass, very clear mids and precise highs, completely different sound to other Bose products.

I have only 2 cons for them (the QC2): 1- their $300 price tag and 2- once your out of battery you can't use them as only audio (without cancelation) headphones; although they can run for 40hrs with one single battery. I have used Sony's version of these headphones and even though they're much cheaper they are very poor in performance when compared to the QC2s. Another very good pair is Senheisser's 450 series, but as their name infers are worth 450 bucks and is like putting on a helmet.

Hope this helped,
-Victor

 

[LethalWolfe]

I tried a pair of Sony's once (don't remember the model number) and they gave me vertigo. I couldn't wear them more than a few minutes w/o feeling nauseous.


Lethal

 

[ethernet76]

I'm not looking for recommendations, but I'm wondering more how they work. I understand that they generate frequencies opposite to the ambient noise, but does that mean that these sounds wouldn't hit my eardrum, or would both the noise and the cancelling-out noise hit my eardrum? Basically what I'm wondering is whether the noise disappears or if it is doubled but just becomes inaudible to me?

Neither hit your ear drum.

Since sound travels in waves, it is possible to measure that wave, create the inverse and have them cancel each other out.

Fun example. Take a slinky and stretch it out to 20-30 feet. Have a person on each end jerk their hand to the right at the same time using about the same force. When the two meet in the middle the slinky should be completely straight.

Sound works the same way.

That doesn't change the fact in-ear monitors are better at noise cancelation than any active system like the Bose QC2s.

 

[Victor ch]

...
That doesn't change the fact in-ear monitors are better at noise cancelation than any active system like the Bose QC2s.

I know, also they don't require additional power. But, Im not a big fan of sticking small earbuds into my ear canal. I have a pair of in-ear headphones (non canceling) and I find them to be the most comfortable in-ears I've tested, still they fall short in comfort compare to the QC2. I mean boy they are easy to wear, I used them for several hour straight and they didn't make me uncomfortable, something other headphones I testes can't match. And if for example you find the airplane's rumble to be annoying you can't just pause the music (in the in-ears) and expect them to cancel out that rumble, many of the active ones can. One advice though (to adk) if you end up getting the Bose QC2 or QC3, or for that matter any Bose supra or circum aural headphones do not use any EQ (or use Flat) since they have a technology that auto adjusts the music for better performance (it really does work best with eq off or you'll find yourself with an "overcharging" of sounds that can lead to distortion)

-Victor

 

[Mammoth]

But rest assured, headphones that eliminate noise by just blocking it works better. Noise-canceling headphones need power, and that has to come from somewhere. Shures isolate noise exactly like earplugs so their models and similar designs are unparalleled.

 

[monke]

I tried a pair of Sony's once (don't remember the model number) and they gave me vertigo. I couldn't wear them more than a few minutes w/o feeling nauseous.

I waited nearly two months to get my hands on a pair of Sony Noise Cancelling headphones once. I put them on, played about 30 seconds of a song and returned them the next day. I can't stand the white noise in music.

But rest assured, headphones that eliminate noise by just blocking it works better. Noise-canceling headphones need power, and that has to come from somewhere. Shures isolate noise exactly like earplugs so their models and similar designs are unparalleled.

Shures are amazing. I returned my Sony noise cancelling headphones and paid the extra bit for Shures and I've never looked back. The sound isolation is nothing like noise cancellation. It's like having an earplug in your ear or an ear muff with somebody whispering. There's really no comparison in my mind.

 

[JNB]

Non-active 'phones or earplugs don't eliminate noise, they attenuate it. It's still there, but the amplitude is reduced across all frequencies (not perfectly equally, but close enough for the discussion).

Active noise cancellation is fairly selective, and in my experience provide the benefit of canceling the more irritating (and damaging) low-freq, steady noise, but I can actually carry on a conversation while wearing them. It really depends on your specific need as to which method ends up better.

I've had QC2's for three or four years now, and they've been with me on about 500 flights so far. I've tried a plethora of other methods and brands, and in that particular environment, nothing works better. On my motorcycle, though, simple disposable foamies are better. Like I said, it depends on the activity & need.

 

[Mammoth]

Shures are amazing. I returned my Sony noise cancelling headphones and paid the extra bit for Shures and I've never looked back. The sound isolation is nothing like noise cancellation. It's like having an earplug in your ear or an ear muff with somebody whispering. There's really no comparison in my mind.

The cable on my Shures broke. There's something messed in the area where the cable splits and my warranty is through this spring. I better act soon.

 

[Drumjim85]

One thing you have to keep in mind is phase, and when the headphones add noise, which these do, its going to affect how your medium (music, movies....) sounds.. I can't deal with knowing I'm listening to an altered medium. So I prefer noise rejecting over noise cancelling.

 

[motulist]

It's basic Physics 101. If it sounds less loud, then you are actually receiving less sound energy in your ears.

If 2 sound waves entering the air around your ears at the same moment are at the sound wave levels of

(+2 in the X direction)

and

(-2 in the X direction)

then

+2 - 2 = 0



I've obviously simplified things a huge amount, but that's the basic principal of what happens with noise canceling headphones.

 

[JNB]

One thing you have to keep in mind is phase, and when the headphones add noise, which these do, its going to affect how your medium (music, movies....) sounds.. I can't deal with knowing I'm listening to an altered medium. So I prefer noise rejecting over noise cancelling.

The active sets (at least the Bose) sample exterior noise sources. The interior sources (from an iPod, stereo, TV, whatever) are unaffected.

 

[Victor ch]

Non-active 'phones or earplugs don't eliminate noise, they attenuate it. It's still there, but the amplitude is reduced across all frequencies (not perfectly equally, but close enough for the discussion).

Active noise cancellation is fairly selective, and in my experience provide the benefit of canceling the more irritating (and damaging) low-freq, steady noise, but I can actually carry on a conversation while wearing them. It really depends on your specific need as to which method ends up better.

I've had QC2's for three or four years now, and they've been with me on about 500 flights so far. I've tried a plethora of other methods and brands, and in that particular environment, nothing works better. On my motorcycle, though, simple disposable foamies are better. Like I said, it depends on the activity & need.

Glad to see that QC2's can last so much, I got mine for christmas. I find that if you combine music (with volume just a little bit over half) and their cancelation circuitry you will hear nothing. I mean, I put my QC2 put some tunes and find myself drooling away in my music unable to hear outside noises unless they're very loud (like a car horn or someone yelling pretty loud). Something that for me is one of the key factors is comfort, in-ear can hurt my ears after 2-3 hours of use while the QC2 can stay there for a very long time.

-Victor

 

[motulist]

The active sets (at least the Bose) sample exterior noise sources. The interior sources (from an iPod, stereo, TV, whatever) are unaffected.

"In theory, there's no difference between theory and practice, but in practice, there is." - Yogi Berra

In theory, noise canceling headphones would only produce sound waves that are the exact inverse of the ambient sound waves that would otherwise enter your ear, and thus perfectly cancel out the ambient sounds and prevent you from hearing them.

In practice, the headphones are only able to cancel out some of the ambient sounds that would otherwise enter you ear, and any waves it produces that are not exactly inverse of the incoming ambient sound waves will instead just be extra noise that gets added to what you hear.

disclaimer: I've never used noise canceling headphones myself, I'm simply clarifying the ideas expressed in the posts above.