the 50mm vibration transducer  produce sound through direct vibration of the bones in the head or are capable of converting surfaces into speakers via vibration when placed on materials such as desks, walls, doors, and many other materials.

 Creates sound through vibration transmission 
• Turns nearly any surface into a speaker 
• Cushioned stand keeps your surface scratch-free 
• Wide 300 to 20,000 Hz frequency response 
• 4 ohm impedance and 20W power handling