MDP to HDMI: No Sound

hello,
purchased 27in imac last week! bought minidisplay port hdmi adapter sound monoprice. unfortunately, cannot sound come out of tv no matter try. have tried changing resolution of screen, changing sound setting hdmi plug (it recognizes it...), nothing seems work. sound comes though imac speakers, no matter options choose. have insight?

 

and reset pram command, option, p, , r. doesnt recognize hdmi, , when plug in, screen flashes blue several times.

 

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