Huwag direcho ang butas. Butas ka muna sa isang wall, tapos padadaanin mo ang cables sa loob ng wall. Labas yun sa isang wall about 1.5 meters ang layo from bawat butas. Fill the inside with glass fiber. Better, instead of using snake cable, use a conduit, about 2" radius, then insert the cables inside. Fill the mouths with glass fiber so that sound can be absorbed and it will be somewhat soundproofed. Otherwise, your conduit will be a medium where sound can pass.
FWIW