Electrostatic, Electromagnetic, temperature differences, thanks to that also arising pressure differences underground - "unexplainable" sounds may appear weeks after lightning.
Umemetuamo, sumakuumeme, tofauti joto, kutokana na kwamba pia kutokana shinikizo tofauti chini ya ardhi - "hayaelezeki" sauti inaweza kuonekana wiki chache baada ya umeme.