In an electroacoustic transducer, the part that initiates the radiation of sound vibration. A speaker cone or an earphone diaphragm are examples.
"We just wanted to send a great big thank-you for the GREAT job you did on our transfer. My husband loved this particular Christmas album and it is not available in any other format. The job you did transferring it to a CD is amazing. The sound clarity is more than we could have hoped for in a transfer. We will sure look to you for other jobs in ..."