I have an audio popping sound on channel 567 in the Ottawa area. I have never heard this pop on any other channel. It is completely random, and can be very loud or very slight. This issue has existed since I started watching channel 567 back in April 2011. I have a SA8300HD box connected via HDMI to Denon AVR-591 receiver.

Could it be some kind of electrical interference?
Bad HDMI cable?
Why would audio pop only occur on this channel?

Thanks for reading.