This practice produces incredible sexual stimulus but be warned that it also leads to some very nasty infections. Even using sterilised sounds (rounded metal probes) I have had more than a few bladder infections over the years. It is something you would do to yourself but not something that you would want to let someone else do to you - the likelihood of damage to the urethra or bladder is extremely high as the other person has no idea of where the sound is or how deep it has penetrated.
