Thunderbolt to Firewire adapter - weird noise?

I added a Thunderbolt to Firewire adapter this weekend and started to do recordings. My first camera is the primary shot and the secondary one is a stationary wide shot. I turn camera 1 off and sometimes it’s doing a “buzz” in the audio. The CPU monitor never goes above 25% - this is on a 2011 iMac with the i5 processor and a 500G drive and 4gig of memory. Any thoughts/ideas?

Ours used to do that, I have concluded that it happens when you have the audio and the video coming thru the firewire cable. I have then switched to only the video coming thru the firewire and the audio coming thru a line in. It seems to me that it gets weird when you have so much data coming thru the pipe of a firewire cable, but yet thats what firewire was designed for. Anyway hope that helps, you might wand to try that if it will work in your situation.

@HeartlandTech: What do you mean by “turning the camera off”? Are you using the “Audio Only”-Layer? In a multi cam setup we recommend to set the “audio input” at the camera sources to “none” and create a single audio source that is attached to the Audio Only layer, so that a camera switch don’t affect the audio channels in any ways.