Sometimes its the wiring inside that makes the vibration. Do you have an aftermarket sound system installed? Thats also a problem for me, still thinking of a solution sans having to install sound insulation (medyo mabigat kasi kaya nagaalangan pa).
*M54 Powered
random kasi pag nagkakaron ng noise e. usually habang umaandar biglang magkakaron. after a few seconds, mawawala. maya maya iingay nanaman. hindi naman malakas vibration ng engine especially when idle kaya mas nakakainis lalo kasi maririnig mo yung noise hehe.
*ILuvDetailing
stock lang yung sound setup ng ek civic ko e..
maingay interior ko kapag nalulubak.... wala nako makita problema.... kahit yung rb10 ko (pioneer box add on) secured naman. Must be the amount of audio cable in my dash? dami eh. hehe....
check mo lahat kasi baka may mga loose bolts and nuts sa interior mo lalo na pag lagi kang nalulubak.. yung mga plastic tabs minsan nagloloose din yun tapos while you're at it palitan mo na rin yung weather strips mo kung sa tingin mo hindi na ok...