[wanderfowl]

For what it's worth, this only works if the source of hearing loss is conductive (e.g. eardrum or the ossicles). If your cochlea or any sub-element (e.g. inner hair cells) are damaged, bone conduction will be no different. In fact, the comparison between acoustic and bone-conduction hearing tests is a key element of audiological testing.

[alecst]

True. The classic tuning fork test: hit the fork, hold it up in front of your ear. Can you hear it? Then gently press the end of the (still vibrating) fork against your skull. Can you hear it now? If no/yes, the loss is conductive. If no/no, it's sensorineural.