I am hearing a jackhammer like sound in my house. It's happened twice now. One per week around the same time. It happens from 6:20AM and stops around 6:35AM. It pulses for about 3 seconds, then stops. Then repeats in about a minute. It's louder in the upstairs on my house. Sounded like it was coming from the attic so I looked around up there--heard the sound, but it didn't sound any louder, nor could I identify it.

Noises and smells are the hardest to track down if we're not there to see for ourselves.
Luckily you have one of the easier ones. Noise = vibration and the louder the noise the more forceful the vibration. Can you feel any vibration starting where the water enters your house? Somewhere it's going to be stronger then other places. That's where to start checking. Good luck, Tom

Jackhammer sounds like air in heat do you have steam?do you have a heartford loop on system? That is a must in steam system

Someone suggested it could be a woodpecker on my chimney, downspouts, or gutters. Seemly awfully loud to be a woodpecker but could be. It only loud upstairs in my house.. Nowhere else.
No Steam.

Lol don't laugh that's what I get early part of spring it is a woodpecker pecking on the ceder shake lol on the upstairs bedroon wall you hit it right on the head.