Two better than one, at least in the case of microphones !

Well many of you might have noticed an extra microphone on the top or backside of your smartphone , and might be quite curious about why this have been placed there , or why is it even existing in spite of having a primary microphone ?

Well the answer is noise cancellation !!  

Even though much technological advancements have been made in the field of smartphones, it does not really become a smart piece of thing when it lags in its most fundamental and basic use, for the purpose of communication. Often we face this problem that when we are outside, the noises around tend to effect the voice signal by a very significant amount. The other end receives a signal that is mixed up of noises around along with the feeble voice of the caller which gets heavily attenuated due to those external disturbances.

The answer to this was to design a noise cancellation technology. Out of the many alternatives, this passive system of two microphones on a smartphone is till date the most effective and simple option.

Basically, a secondary microphone is installed in such a place so that it is at a distance from the user’s primary microphone, which the user uses to make phone calls. Being open to the outside, the secondary microphone can very effectively pick up the external disturbances.

When the user speaks in the primary microphone, the primary microphone receives an input signal of voice along with the noises. Whereas, the secondary microphone is only picking up the noises. By a simple differential calculation within the phone’s processor, a smart piece of software can easily eliminate those noises by taking the reference level as the input of the secondary microphone. This result in a much more clear sounding voice, and also the noises gets heavily attenuated, so we can speak naturally on a busy road in the same way as we speak in our home.

This passive way of noise cancellation is present in the lower mid-range smartphones to even some of the flagship products.

Another interesting use of the secondary microphone is that, it doubles up as a set of stereo microphones in conjoint to the primary one, when we capture video in a landscape mode. Also the same thing is done when we turn on sound recorder. It provides a better depth of the audio signal and it feels more realistic.