Automatic noise cancelling microphone *systems* for consumer devices typically involve 3 carefully placed DMIC's (digital microphones) and a lot of DSP. 73 de AI6KG
On Sun, Aug 5, 2018 at 2:09 PM, Jim Brown <[email protected]> wrote: > On 8/5/2018 10:48 AM, ANDY DURBIN wrote: > >> Many/most aviation headsets use noise cancelling microphones but they are >> not active. They simply sample most of the voice signal on the mouth side >> of the element and most of the noise on both sides of the element. >> Effective noise cancellation requires the microphone to be close to the >> lips. >> > > Not quite -- it's the cancellation of the output of two closely spaced mic > capsules, and as you describe operation, it depends on the mic being right > at the lips. This is the proper definition of a noise cancelling > microphone. Noise cancelling microphones tend to sound varying degrees of > awful. Many years ago, Shure, one of the better mic mfrs, tried to build a > noise cancelling mic aimed at drummers. I tested a prototype in a high > quality recording setup, and it sounded pretty bad. They never marketed it. > > Note that this definition is VERY different from a cardioid microphone, > where a single capsule as two openings, one from the front and one from the > rear, and the two types behave VERY differently. Cardioid mics have a > property called "proximity effect" which boosts bass response when the mic > is very close to the sound source, making it sound rather muddy. When mics > like this are used for singers and speech, their low frequency response is > heavily rolled off. In some mics the rolloff is built in (the Shure SM57 > and SM58 are examples), in some it is built in but switchable (the Shure > SM81 is an example), while in others it is not built in, but applied in the > mixer for sound reinforecment or recording. > > I mention this because many mfrs of headset mics falsely describe their > cardioid mic as noise cancelling, which it is NOT. It IS a directional mic > that rejects sound coming from directions other than the front. > > 73, Jim K9YC > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
