Here are some screenshots from a sound meter app I used on my phone. My phone has mics on both ends of the phone so I just placed it between the earcup on each phone set. I waved a gold wedding band, penny, and dime across the coil (with pauses in between) and recorded the resulting audio graph. The phones tested were: The ML wired phones that came with the 600The LS.Pelso WP Phones from KellycoThe ML WP PhonesCustom modified GG AmphibiansResults: LS.Pelso's best volume, sound quality, sound iso