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Stethoscope Microphone



Stethoscope Microphone

Along with narrowly focused and wired remote microphones, there are devices that record vibrational vibrations of walls, ceilings, stacks, ventilation shafts, etc. These devices are called stethoscopes microphones. They are a rather complex device. Therefore, the device, which can serve as a prototype of the 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 DA 1 chip of the K140UD6 type . 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 the KT315 type and the UT 2 of the KT361 type 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 amplify the signal to the desired magnitudes using an additional audio amplifier . The signal to it 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 .