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Chris2591
5th Aug 2019, 21:10
Hi all,

Firstly, apologies if this is not the correct place to post this question.

I have a Sennheiser HME100 headset. Recently it appears to have developed an issue where the mic is transmitting the ambient sound of the cockpit back to myself and passengers. In some aircraft, the noise is constant and in others the noise is on and off. It is rather annoying and such a distraction. Apart from this, the headset works great.

The issue is only internal, the PTT works as normal.

My question is, is there something on the headset that could be causing the issue? Does the mic need a certain volume to "activate"?

Your help is greatly appreciated.

kind regards,

Chris

ampclamp
6th Aug 2019, 01:00
Sounds like it has a VOX (Voice operated transmit) or open mic happening. VOX operated mics will work if there is sufficient background noise. I'm not familiar with the model. Is there a VOX feature?

In a quiet cockpit I assume there is no unwanted audio being transmitted, but it will transmit if there is louder background noise?

Tried it in other aircraft? Another headset in the one you are flying?

Uplinker
6th Aug 2019, 04:00
Do you use a microphone windshield? (a foam cover)

Many pilots do not, so as well as being difficult to be understood by ATC owing to audio distortion caused by plosive sounds, the microphone gradually fills up with crud. Aviation microphones have a passive noise cancelling feature which reduces cockpit background noise from the mic - as long as the mic is clean internally, has a windshield and is placed very close to your mouth. If crud builds up inside the mic, the noise cancelling feature stops working and your mic puts more and more background noise on your transmissions, which sound noisier and noisier.

This noise might be what is triggering the VOX of your intercom, (if fitted). If so, there might be an adjustment control of the VOX switching threshold on the intercom unit.

hoss183
6th Aug 2019, 11:38
Noise cancelling mics have 2 microphones, one which picks up the ambient sound another your voice, and it subtracts one from the other. It could be its faulty and the wrong mic is feeding through, but i've also seen models where the ambient mic is on the back of the boom, if you have it rotated the wrong way voila.