Totally agree with you, I continually have a battle between "this R/T level is too loud, better turn it down", followed by "what did he just say?, better turn it up again". Some guys on my fleet refuse to go above 280kts in order to keep the noise level down, even if the FMC says 196etc. Anything above about 270 is pretty loud. Once had to do a 1 1/2 hour flight having been level capped at FL190 - 310kts all the way was painful.
There is probably nothing stopping you getting a noise attenuating headset - you can then put it on both ears, use the intercom if required - it may not be needed. Flew with a guy the other day who had one. He could hear me even with the headset on both ears. However, at £400 not cheap. Also, to really work, both guys need to wear them with intercom.
Believe BA 747-400 guys use them with intercom.
I guess we'll have to wait until someone loses there med-cat due to the noise and sues their airline. Unfortunately, only then is something likely to be done. Noise attenuating headsets cost money, and if they don't have to, they won't spend.
Why don't you have a word with health and safety - it's their job to know about these things. If you find anything out, let us know.