Kirwan on Can't turn off sound

Hello, 

I have an Elite 16ch DVR, and two 8MP dome cameras with sound.

I bought these a year ago, but I can no longer find them for sale on the site.

The SKUs are CDE8E3W2-A and PE16P4N8-I.

I would like to turn off the sound completely. I see options for recording sound which you can turn off, and there is a mute button for each camera in the live video feed screen. However, that mute setting doesn't stick. It defaults to the on state at every startup which happens every day for me.

Thanks