dependent pa rin sa material (actually, construction) pero malaki effect ng size and shape. IIRC, sa Mechanical Engineer's Handbook makikita 'to on chapter regarding mufflers. sa Electronics Engineer's Handbook meron din ata on chapter regarding Baffles.
kaya kailangan ng trial and error kasi hindi ka pa rin sure kung tama yung parameters ng unang test "landmine". you're circuit maybe working right but the "landmine" may not resonate at that frequency.
I think the best person to consult with this would be a physicist, or a mechanical engineer.