If you are not aware of the BH-905i, check my Unboxing gallery and my First impressions post.

BH-905i

The Nokia Bh-905i that i have been playing with for a while, has a very interesting feature, which is the USP of this device imho.Its called Active Noise cancellation (shortened as ANC).I am going to discuss this feature in detail after the break.

Now what is active noise cancellation ? Simply put, it cancels the surrounding noise that affects you, in realtime. Note that it doesn’t actually cancel ANY noise, but only ambient noise that is persistent around you, but in a wide range of frequencies.

so,how do you activate it ?

Active noise cancellation switch

The Active noise cancellation switch is present near the charging port of the BH-905i. So just push the slide switch to activate the ANC(the LED near the switch turns green),and when you do that , multi array mics present in the BH-905i get activated. Note that it will take a few seconds to start the process, you may find out why soon, below.

Now,lets see what Nokia has to say, about this technology :

Wolfson AudioPlus[TM] Ambient Noise Cancellation technology uses
patented signal processing technology and advanced acoustic design
expertise to deliver class-leading active noise cancellation for stereo
headsets and headphones.
This novel feed-forward technology cancels more decibels of noise
across a wider frequency range than traditional feedback technologies,
providing a peaceful and tranquil environment for users wherever they
happen to be. As Wolfson’s advanced technology does not process the
playback audio stream, your music comes through in untouched hi-fi
quality stereo.

So according to Nokia, it is also called Ambient noise cancellation, which sounds more truthful to its doings.And it does not process your playback audio, it comes untouched. Intriguing to know how, right ?

From the above quote you can notice that it uses Feed forward technology to cancel the ambient noise. So, what is feed forward technology which plays a key role in this whole ANC thing ? i asked my friend Wikipedia and the good ol’ myself in college(being an engineer) for help and this is what i inferred :

First, let’s see what feedback is.In Control systems, for example, lets take a user interactive system, a process(the input) goes through some operations to give the output, the sample of the output is taken back to the input for reference and thus feedback is implemented. So, the difference between the input and the output is taken as feedback . Now, the exact opposite of this is feed forward. What happens is,the processing is done before the input and thus you get pre-defined set of operations which doesn’t act according to the output. This is what exactly happens in the Noise cancellation of BH-905i, the operation of eliminating the noise happens pre-defined, and so it does not touch the audio that plays through your headset.According to nokia, this setup is far better than older feedback based noise cancellation techniques, and i can see why.And since it pre-processes the noise cancellation, it takes 2-3 seconds for activation in realtime, now you get it, right ?

Now that we know what active noise cancellation is, let’s see some practical usage scenarios.

If you happen to travel a lot, using public transport , the ANC may prove very useful. For example, while traveling in my city transport bus, i preferred to use the BH-905 i, just pushed the ANC switch and bang! immediate silence.And while riding as a pillion on a bike, the ANC caused a lot of noise, quite the irony,eh ? while trying hard to cancel the noise, it lets in some whisshing sound of air , surely ambient noise is canceled but sadly, the effect is spoilt while riding in an open vehicle.

One more intriguing use of the ANC is its offline capabilities, i mean without being connected to the phone, you can use the ANC, just like that. Well,if you are in a noisy surrounding, and not in the mood for a song, just push the ANC switch and have a drink, in peace.

So, thats it from my side, about the Bh-905i’s USP ,the active noise cancellation. I have told you what i know. Now i need feedback from you.

Like the article ? What more features of BH-905i should i cover in the full review?

Comments section is open for discussions 🙂

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Comments on: "Active Noise Cancellation – BH-905i [Feature]" (4)

  1. […] Before you start reading this, just make sure you have read these :- BH-905i Unboxing , BH-905i First impressions , Active Noise cancellation feature. […]

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  3. I have bought the BH-905i recently. The premise I had in my mind to justify for buying this high-priced headphones was that it would kill 99% of the background noise as advertised by Nokia. To me this seemed revolutionary; being able to talk in the noisy city traffic and the other person also believing that I am strolling through some reserve park or something.

    However, I am far from impressed with the Active Noise Cancellation capabilities (be it feed forward or whatever):

    1) Receiver side noise cancellation: This is supposed to create a cancelling sound field around the ear exactly opposite in phase to the background noise. This should allow you to hear clearly in busy streets. However, BH-905i does not truly kill 99% if background noise as advertised, it merely reduces low frequency hummimg noises effectively (like the aircraft engine, the air-conditioner noise, or the the din of an office). It effectively does not reduce high-frequency noise or varying noise such as car horns, or sudden noises. On the contrary, it introduces an audible hiss in the sound stream. You can understand this by just flicking on then ANC switch in & off without connecting the headset to audio / voice. I believe that the hardware is not fast enough to create anti-noise in the correct phase, so the stuff works well for constant low power humming noises only, That’s not what I was expecting considering the price. The same effect can be achieved by much cheaper passive noise cancellation techniques (in year headphones or over-the-ear type of headphones).

    2) Noise Cancellation for my Voice: This is supposed to filter out my voice from among the background noise and deliver it to the listener on the other end (the person who I have called). BH-905i does a very lousy job in cancelling noise. The person on the other end is barely able to hear my voice and the background noise remains high. In fact, I have to talk very loudly so that the other person is able to make out my voice from the background noise. In the same location, I have used my Samsung Galaxy S2 handset directly, and it has given astonishing results. The phone has a dual mic for noise cancellation and is very effective (most of the times the person on the other end is unable to make out whether I am at my home or in a busy intersection). Unfortunately, BH-905i fails miserably on this front.

    3) Cancelling noise in the voice (eliminating noise from the voice signal of the other end): Suppose the person who has called you is in a busy street and you are in your office. If your headset is able to use DSP based noise filtering algorithms to enhance the voice quality and reduce the background noise, it would have been a great thing. BH-905i does not attempt to do this (i am not aware if there are others which do this).

    Overall, the ANC for this product is not as good as it is advertised. Let me know what is your experience with BH-905i.

    • Hi.. Thanks for the most elobarative comment. As for the issues you have mentioned, i didn’t quite notice them.

      1. I don’t think thats how it works. It cancels the ambient noise very well, but i agree it adds a hissing noise when activated, not so noticeable under noisy situations though.

      2. During calls, i am not sure if it does noise cancellation for your voice. Because that is not the function of noise cancellation in BH-905i. It is plainly used to cancel the ambient noise when you listen to music. A luxury perhaps. However i acknowledge your point, it is valid indeed, my N8 has better noise cancellation during calls.

      3. That is not possible i think.

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