Why does my insert sing?

[traviswalken]

I recently purchased a Hampton HI300 and am really enjoying it. However, I am perplexed by one of its quirks...or maybe all insert do this.

I typically get the fire started and leave the door ajar for about 3-5 minutes, close door with air open (10 minutes +/-), then reduce air. When I reduce the air it typically makes a high pitched hum that sounds like someone blowing onto the top of a pop bottle. It is almost as loud as the fan on high. It typically lasts for a minute or two.

A couple evenings ago, it lasted about 10 minutes. When I messed with the air controller it didn't stop. It finally stopped when the fan kicked on.

This isn't a big problem, just wondering if this is typical.

I am guessing it is related to air being reduced.

 

[midwestcoast]

I had what is likely the same problem with the Hamptons cousin, I-2400. Several other Regency/Hampton owners have had this issue & it generally turns out to be from the "EPA hole". Hopefully it's in the same spot as mine: To find it you need to detach the blower, then look over on the right side directly across from the hole that the air adjustment rod goes through. Try plugging the hole while it's making the noise to see if it stops.
If yes there are basically 2 options. #1 is block it with something non-combustible. I used a magnet, but tinfoil or whatever would work. Option #2 is to get a little file in there & smooth out the edges of the hole, especially the inside edges. Burred edges on the hole are supposedly the problem
To pick an option you need to know why the hole is there. It is there because EPA mandates that the fire must always get enough air to burn cleanly (in theory) even with the air shut fully. So the manufacturers set the stove up to get enough air to satisfy the requirement during a test. If you block the hole even partially you are reducing the amount of air the fire can get and so you must never close the air control fully or you'll end up with lots of smoke & creosote but no fire. Do that enough and you're headed for a chimney fire.
Only down-side to smoothing the edges of the hole would be that it's probably a tight place to try to file anything.

 

[traviswalken]

Thanks for the info midwestcoast. I'll take it apart in the near future and confirm the source of the noise.