When we talk about PC microphones , many times we see that they have the characteristic of having noise cancellation , be it active or passive. This ability is especially important in streaming devices since they manage to eliminate or alleviate background noises, but do you know how this noise cancellation works? In this article we are going to explain it to you so that you understand its importance.
Whether it is for amateur or professional streaming, or simply to be able to talk with your friends when you play or to hold meetings while you telecommute, having noise cancellation in the microphone is very important to have a good quality and experience of communication. Next, we are going to explain how this interesting feature works.
How does noise cancellation work on microphones?
The principle of this feature is that there are really two identical microphone elements within its encapsulation, connected to each other and staggered as you can see in the following figure.
Any sound coming from afar reaches the two elements as a pair of practically identical acoustic excitations, each one being picked up by the two elements and processed to generate an electrical output. The principle of noise cancellation is that when the audio source is detected to be far away , one of the two elements of the microphone will generate a normal output, while the other will generate it the same but inverse . Due to their arrangement in phase, the two output signals oppose and cancel each other.
This is what is called active noise cancellation .
However, if the acoustic excitations emanate from a nearby sound source and each arrives outside of the microphone pick-up axis, the stimulations of the two elements are uneven and their outputs can only be partially canceled. As a result, there is an electrical output signal in response to the nearby sound, and in other words, if the sound is detected to be close it will not be canceled.
The underlying assumption is that a nearby sound source is coming from the human speaking into the microphone, and therefore does not want it to be canceled. Although there is always some critical axis that would cause the cancellation to occur, this is very small and the manufacturer already takes it into account when positioning the microphone encapsulation, so it is not something we have to worry about. general way.
The bottom line of all this is that noise canceling microphones actually have two microphones; When it comes to processing the signal, if it is captured that it is coming from far away because they enter the microphone practically on the same axis, one of the microphones generates an inverse signal to cancel the other, eliminating background noise. If, on the other hand, the sound arrives in different axes, it is detected that the source of the sound is close, it is assumed that it is the human being speaking, and therefore the signals are not canceled, then generating the correct electrical signal.
Passive Cancellation
Some microphones also have noise cancellation but do it passively, although this is more common in headphones. It really is a fancy way of calling the effect you get when using the device, as it depends solely on the physical characteristics of the microphone, such as the design and materials used.
For example, the manufacturer can install an internal pop filter (which almost completely cancels the effect of the “wind” that we expel through the mouth when speaking) and considers this to be “reduction” of noise, or they can integrate the condenser microphone in the center at a certain distance from a mesh that only allows certain frequencies to enter, canceling out the others. This type of cancellation is relatively better at filtering out irregular high-frequency sounds, but it is certainly not as effective as the active one that we explained in the previous section.