Beyerdynamic HS 400 buzzing noise
 

Hi everyone,

I'm using my personal Beyerdynamic HS400 as headset in the A320, on some aircraft I have a really loud annoying buzzing noise. I get this noise when talking, or just when the interphone is active. It's a lot louder when I come closer to the windshield so I think the problem is with the 400Hz static noise coming from the window heating...?
In the pictures below you can see that I have a converter from 2 pins to the airbus XLR 5pin, however, when i opened op the converter I see that 1 pin is not connected?

Do you have any solution how to fix this?

https://i.imgsafe.org/e81a5e9589.jpg
https://i.imgsafe.org/e81a6bb9dc.jpg
https://i.imgsafe.org/e81a799622.jpg