David Harbin:

>I took my revenge by playing the battle scene from Struass' Hero's Life
>VERY loudly (RSNO/Jarvi)and this stunned the little brat into silence for
>about an hour.

To send the same message, you might consider playing the same piece each
time this happens.  The risk you are taking is that, if the problem is
callousness, rather than unawareness of the thinness of walls, the offender
may escalate.  Also, there is the possibility that a third neighbor might
intervene by calling the authorities.  The best course might be simply a
polite, direct discussion with this person.  Sometimes that works.

Jim Tobin - who recalls past torment of this sort.