I have 2 Sharp aquos tv's and our 42" lcd has sound issues. The TV is not hooked up to any receivers but the sound is wrong.
What i experience is hearing background music or crowd sounds at sporting events that seem to over play the announcers voices. My 32" Sharp does not do this. I can't figure out why it does this and find it very annoying.
Today for example watching football I could barely hear the play by play announcers over the crowd sounds.
You should also check your source device (i.e. cable set-top box) to ensure that both TVs are set to use Stereo output and not 5.1. If the STB connected to the 42" TV is set to output 5.1, then it would explain what is happening, since the TV wouldn't have a dedicated center channel (where the announcer's voice would be coming from).