RCA surround sound system goes silent on quiet noises

[Shalak]

For the audio of my PC setup, I am using an RCA (the company, not the cable) surround sound system that my friend gave me, which is technically designed for TVs. It generally works fine, except whenever I am watching something that has quieter noise in the background, during which the system doesn't pick up on the sound unless it is using an HDMI connection. This is the case when connected to a TV as well. I've tried using an HDMI cable for sound, but my PC won't recognize it, so I have to use an auxiliary cable, which causes the speakers not to pick up on the quiet audio. Any thoughts?

 

[jFiveNYC]

What cable are you using if not the HDMI cable? What output jack of the computer are you using to send audio to the RCA audio system?

Typically movies and television that have been mixed for surround sound setup, will designate certain audio for the rear speakers in the surround sound system. If nothing is receiving rear audio channels or mixing the stereo 2.0 audio to accommodate for a lack of true surround input, those channels could be lost. An HDMI cable and connection with a spec of 1.3 or newer, will carry true digital 5.1 and 7.1 surround sound.

Would you please supply the model of the RCA audio system AND either your computer, dedicated sound card or motherboard with integrated audio?