I have replaced the noise filter and checked the jacks. It does not matter what headset or jacks are used. I replaced the audio panel and had the radio serviced. When I transmit all I hear is a low screech. Others simply reply to transmissions with a simple I cannot understand anything.
Two people can talk inside the airplane with no noise and reception is clear. I have also checked voltage and connections going to the radio as well as installed a new high quality line filter. Both push to talk switches cause the same noise, I have tried flipping things on or off running the trim etc. no change.