Here's what I use on the "Bus" to protect my hearing from co-workers who turn their speakers up to 120db because they are already half deaf or to minimize the wind noise at 320 KIAS. Below 18 I use the existing aircraft headset. Then I use an old school Telex headset (from my Boeing days) with just an ear mold to fill one of my ears while an ear plug fills the other. The Telex plugs in with just one plug below the existing aircraft headset jack(most guys don't know this) for audio only and I use the hand held microphone to talk. Simplifies donning the O2 mask as well, no headset to remove and no speaker required to hear. Depending on how interesting my co-worker is to talk to is how deep I insert my ear plug.