pirates of the Caribbean on bluray...lpcm

I have a question regarding lpcm audio at 6.9 mbps on this bluray versus the DD 640 Mbps audio.I am using HDMI from bluray to reciever and its easy to compare the two going back and forth between the audio surfing my tests in various scenes.My question is why is the lpcm audio of a lower volume and seem to lack micro details that you can clearly hear in the DD track via my back and forth tests?

Thanks for any input