Invite people to your house, give them a tour and briefly mention the shelf before scurrying them on. Watch their faces contort but don't give them the opportunity to ask any questions.
EDIT: I have a vague guess at what could have gone wrong with your adaptor. It might have had OK L and R contacts but a broken G contact. You would then hear the difference between the L and R channels, which most often sounds like garbage. Music would be weird (entire instruments/vocals disappear) and mono audio would be silent or near-silent (so you'll have to turn it up a lot and will hear noise).