Mystery noise in flue (no, it's not a critter)

  • Thread starter Thread starter DaveC426913
  • Start date Start date
Click For Summary
SUMMARY

The forum discussion centers on a peculiar noise emanating from a chimney flue, described as a sharp, rapid "whamming" sound occurring 10 to 15 times per second. The noise is suspected to be linked to the recent switch of the forced air furnace from heating to cooling, potentially involving a malfunctioning damper or an active flap within the chimney. Various theories are proposed, including the possibility of a woodpecker or a mechanical issue related to the HVAC system. The discussion emphasizes the need for further investigation, such as using an inspection camera to explore the chimney's interior.

PREREQUISITES
  • Understanding of HVAC systems and their components, particularly dampers and flaps.
  • Familiarity with chimney structures and potential wildlife interactions.
  • Knowledge of sound frequency and resonance principles.
  • Experience with inspection tools, such as sewer inspection cameras.
NEXT STEPS
  • Investigate the functionality of the chimney damper and its connection to the HVAC system.
  • Learn about chimney inspection techniques, including the use of inspection cameras.
  • Research the behavior of woodpeckers and their potential impact on chimneys.
  • Explore sound resonance in hollow structures to understand the noise characteristics better.
USEFUL FOR

Homeowners experiencing unusual chimney noises, HVAC technicians diagnosing potential system issues, and wildlife specialists addressing animal interactions with residential structures.

  • #31
I confess I do hear a similar noise a little bit when there's rain or wind. It's not the same fast whamwhamwham - it sounds just like a flapper you'd hear weakly opening and closing with a pressure change in the house.

So my best theory is that there's a butterfly valve that can be gently disturbed by pressure changes, but it also has a motor attached or something that whamwhamwhams it about at certain times - presumably when the A/C turns on.
 
Engineering news on Phys.org
  • #32
Remember a clarinet is just a tube with a flap valve (the reed) at one end. The resonance comes from the tube length of the air. My alternate model is more like an harmonica where the resonant frequency comes (mostly) from the reed springy-ness .
Maybe you can put in a keyboard and serenade the neighbors. Sort of a big basso profundo Alpenhorn. Golly I wish my house was musical.......when we annex our 51st state perhaps I can buy one.......(small sardonic joke)

/
 
Reply
  • Haha
  • Like
  • Informative
Likes   Reactions: Klystron, Rive and DaveC426913
  • #33
DaveC426913 said:
No, I get what resonance is in a pipe, but of what?
My thought is, that the frequency is too high for a butterly valve or such to be flapped by just airflow. Something more forceful might be needed, like a tube-length resonance rattling that flap.
hutchphd said:
Remember a clarinet is just a tube with a flap valve (the reed) at one end.
 
Reply
  • Like
Likes   Reactions: hutchphd
  • #34
at our house the northern flickers sound exactly like that.
 
  • #35
Heheh it's not a bird

So, another piece in the puzzle: it is making the same tone during rain. This time, rather than the mechanically perfect beat, the beat is raindrop-random.

So, raindrops are hitting what certianly must be a baffle.

I assume the baffle has some sort of open/close solenoid that's operated by the central air system, but it is perhaps poorly calibrated (badly positioned microswitch), so it "thrashes" for a few seconds before settling to its proper state.
 
  • #36
DaveC426913 said:
So, raindrops are hitting what certianly must be a baffle.
You don't have a cap/top on your chimney?

1751751047251.webp

https://www.amazon.com/YITAHOME-Chimney-Cap-Stainless-Adjustable/dp/B0BX7SDHWG?tag=pfamazon01-20
 

Similar threads

Medical Experiencing a Clicking Noise in My Right Ear - Any Advice?
  • · Replies 14 ·
Replies
14
Views
6K
Undergrad A busy and interesting night sky in Mackinaw City
  • · Replies 1 ·
Replies
1
Views
2K
Can large static discharge cause vision to see white flash?
  • · Replies 8 ·
Replies
8
Views
5K
Did the 1883 Krakatoa Explosion Leave Ships in Peril?
  • · Replies 16 ·
Replies
16
Views
7K
High School Can someone please identify what I saw? (lights in the night sky)
  • · Replies 25 ·
Replies
25
Views
5K
High School What Could Explain the Mysterious Red Pulsing Light in the Sky?
  • · Replies 13 ·
Replies
13
Views
4K
Building a noise detecting circuit
  • · Replies 54 ·
2
Replies
54
Views
11K
News Should I Keep My Bird Feeders After a Tragic Woodpecker Accident?
  • · Replies 42 ·
2
Replies
42
Views
10K
Finding broken wires underground
  • · Replies 28 ·
Replies
28
Views
33K
Structure of the Galaxy: 6 Questions Confirmed
  • · Replies 31 ·
2
Replies
31
Views
4K