I've long wondered about skipping the speaker and just going for a method to create long-waves to vibrate everyday environments. In sync after tuning it could be like a 360 earthquake internally.

If it works for microphones to catch radiant sound (as I learned in on-set film production) then it probably works the other way too (as I learned when in the booth watching a DJ friend plugged his headphones into the mic jack and used one earpiece to talk to the crowd).