Sympathetic vibration

- [Instructor] The fundamental physical principle … at the core of this conversion is sympathetic vibration. … Although there are all sorts of different ways … to complicate the explanation of sympathetic vibration, … it's really pretty simple. … Consider a timpani. … If the head is tuned to the note F … and the orchestra plays the note F, … (orchestral music) the timpani head … will sympathetically vibrate in response … to the acoustical F from the orchestra … without ever being struck by the timpanist. … A guitar string tuned to E in exactly … the same way will vibrate without … (guitar music) being struck when it hears … that note acoustically. … This phenomenon is exactly what happens … to our eardrum in response to acoustic sound. … The tympanic membrane, the eardrum, … sympathetically vibrates in direct correlation … to the acoustical sound wave it hears. … We could also say that the acoustical sound … resonates the eardrum. … Now consider the microphone. … At the core of the microphone capsule is a surface …