pnichols wrote:
We have an automatic thermostat controlled attic fan that makes a low hum that changes/goes away in different parts of the house. Do you have one powered by some breaker that's not getting turned off?
Is the hum caused by the roar of the burner in your gas water heater?
Could it be the wind blowing through your home's crawl space that's allowed due to the outside wall ventilation vents in the crawl space?
Do you have automatic outside sprinklers that may be coming on ... sometimes water running in pipes under the house as they feed outside faucets/valves can almost make a humming sound in the pipes?
Is the step-down power transformer on the power pole that feeds your house humming?
I've ruled out all of that; The hum occurs when the water heater is off; the sprinklers only come on 3 times a week in the early morning; there are no power poles in the neighborhood.
I considered the wind blowing through an outside bathroom exhaust vent, creating a harmonic in the exhaust pipe. I sealed off the vent with masking tape temporarily so no air could get in and it made no difference. I really don't think it is wind related though I considered that. The pattern of when it occurs does not seem related to any wind movement.
I've realized it's more prevalent in the afternoon and rarely occurs in the morning, though it has in the past. It's 7:30 am right now and it's silent in the bedroom. Seems like it was louder than usual yesterday afternoon.
Neighbors on the other side of our block wall in the back yard have a pool and you can hear the pump running from time to time but when the pump is off, the hum is still there.
Somebody mentioned something about a Fire Station and we do have one about 3/4 of a mile away.
