I occasionally hear an odd popping/knocking noise from my laptop. It happens only once per few minutes and is very quiet. It seems to happen more during boot. Sometimes there are long periods without the noise.
Ah. I have discovered the source of the noise I’ve been hearing. It’s made by a combination of the power supply and the fan itself, every time the fan starts. So only when the CPU load is low enough to let the fan stop… eventually enough heat builds up that it starts again.
I think it’s a pulse width modulation-related “chirping” noise from the fan. Especially audible at low speeds, or when the fan turns on and turns off right away. I hear a faint chirp occasionally on my Framework laptop too, but it’s not loud enough or frequent enough to be bothersome.
Yep, this is correct. It’s pulse stretching/PWM chirping as the fan figures out how to spin itself up. We’re not really happy with the behavior, and it’s something we plan to change the next time we source a fan. In the meantime, with 3.03 firmware we’ve reduced the extent that the fan spins up and down to make it more rare to hear the noise.