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Stethoscope Microphone



Stethoscope Microphone

Along with narrowly focused and wired remote microphones, there are devices that record vibrations of walls, ceilings, stacks, air shafts, etc. These devices are called stethoscopes microphones. They are a rather complex device. Therefore, the device that can serve as a prototype of a microphone-stethosco- pa and the principle of its operation are described below . The schematic diagram of the device is shown in Fig. 2.45. The audio amplifier is assembled on a DA1 type K140UD6 chip. Resistors R 1 and R 2 set the mode of operation of the chip. The gain is determined by the resistance value of the resistor R 3. The VT 1 transistors of type KT315 and UT 2 of type KT361 are switched on according to the emitter follower circuit and amplify the current output signal . The amplifier is loaded with TZN-2 head phones . The vibration sensor is made of piezoceramic head 81, taken from an old player. Vibration oscillations are transformed by a piezoelectric sensor into electrical ones and amplified by an amplifier DA 1. Can we use a piezoelectric transducer of the type ZP- i , ZP-2 as a piezoelectric sensor 2? and the like from electronic watches and toys. They reproduce well the frequencies in the range of 800–3000 Hz, which mainly covers the speech range of frequencies. If necessary, you can enhance the signal to the desired values ​​using an additional audio amplifier . The signal comes from the output of the operational amplifier DA 1. A similar sensor can be successfully used as a burglar alarm sensor. For example, PE-1, GZP-308 and others can be used as piezoelectric transducer B 1 .