Although vibration motors are common in Mobile phones, procuring button sized vibration motors were the ultimate challenge. (There were a couple of good ones on ebay, but couldn’t find one at this point of time)
But once that was resolved, one of the leads of the vibration motor was connected to the headphone jack and the ground of the headphone jack to the other lead.
Now square wave signals are played through the headphone jack using Audacity. Although one can feel the motors vibrating, using an operational amplifier such as LM324 helps to intensify the vibrations. ( Power source to LM324 – Battery/Arduino )
One of the weirdest but yet satisfying experience with the vibration motor is when you connect the vibration motor through the audio jack without any amplifier. You can hear the music being played through the vibration motor. The motors seems to be dancing to the music being played. We tried so hard to capture the phenomenon but the sound was too feeble to be picked up. That shouldn’t stop you from giving it a shot.