I don't use Netflix, but is there an audio settings option in Netflix you can try changing.
If you are just using the TV's speakers you could try looking in your TV's audio menu and maybe change either the HDMI audio format or Audio format to something other then Dolby Digital, switch it to PCM or stereo if you have that option, or check if there is a sound setting like clear speech, sport, music or cinema setting that has been turned on.