Can anyone identify this noise coming from my water heater?

We have been hearing a clicking/scratching sound coming from our water heater for quite some time. The clicks are pretty evenly timed and I can't tell what causes it. It happens in the middle of the night when the water is off as well as during the day when we are using hot water. The sound travels through the pipes and we can hear it throughout the house but it is loudest at the water heater.

Here is a link to a recording I made at the water heater: http://picosong.com/fWjG

Can anyone help identify this sound and what causes it?

Thank you so much in advance.

For sounds...........You need a tech to look at it! but I can give you some insight if this makes any sense? Possibly temperature issues with the condensation? or piping expanding and contracting? Or it can possibly be a air issue or a small leak. with an air issue you would need an expansion tank but you really need to have someone come by and take a look, "Free if possible.

Thanks for the reply, did you have a chance to listen to the audio file I posted?

Loose ball check on the inlet or check valve in the system. Could be a malfunctioning PRV. Might not be the water heater at all. Sound traveling through plumbing can be very deceiving.

Even with the recording, this may be near impossible to diagnose without a pro being on site.

Okay, that makes sense. I'll have to get someone to come out.

I appreciate your time!