Aiming at the problem that the acoustic signal is weak and easy affected by the outside noise or electromagnetic signal interference

when it is converted into electrical signal

the polyvinylidene fluoride（ PVDF）is adopted as piezoelectric thin film to convert the acoustic signal to differential electrical signal. The acoustic sensor with high sensitivity is design as cone by copper to form closed environment and amplify the original acoustic signal with the rule of gas compression rule. The random noise interference

and electromagnetic interference are shielded and the signal to noise ratio is increased

so the acoustic signal is stable and accurate.The differential signal is amplified by the low noise amplifier and sent to the module of Bluetooth. The mode of synchronous connection-oriented is adopted in Bluetooth to transmit the signal. The hardware circuit board is designed as circle and welded double side. It is embedded into the acoustic sensor to transmit the acoustic signal wirelessly.