As every new ones first time try any of this ROM family, first and common bug they found is this sound static, squeaking, cracking or whatever you say, is that can be a lifehack fix when any sound play like if you press volume button, and that volume button sound, that instantly fix unless you disable that, to make sure this able in setting->sounds->more sound.
In my case one bug automatically fix that, as with alarm bug, if you have set alarm not matter what time, whenever reboot, alarm start trigger ringing irrespective to time and automatically disappears in seconds, no need to dismiss, well this bug fix static, cracking sound,
man i love this bug! dont fix untill you get fix for static sound.
well, but those isn't solution! everyone knows!
Cheap Solution is if Dev put a startup sound during booting up animation, i know most of us hate startup and shutdown sound, even i hate that, but i am talking about a fake sound, a silent and very low volumed beep sound is enough
hope this helpful