Look at it two ways if you wanna put it in the interior. The first is the noise as was said before and the second is the performance. The noise "hum" is the resonant frequency emitted in the form of electronmagnetic inference. Take this interference into account when installing because I know mine gave some serious radio noise. I put a noise filter in series with it, went to town with dielectric grease on all my ignition contacts, upgraded to better plug wires, and even went and regrounded everything I could and still got some serious radio noise. I think mounting the box as far away from any speaker wires and the local area of your radio should be a good idea when desiding on interior installation as well as it being in the engine bay if you have other items that could be affect by electromagnetic interference.