Principle and application of sound sensor

A sound sensor, which may also be referred to as a sound sensitive sensor, is a device or device that converts mechanical vibrations propagating in a gaseous liquid or solid into electrical signals. It detects signals in a contact or non-contact manner. There are many types of acoustic sensors, which can be divided into piezoelectric, electrostrictive, electromagnetic, electrostatic, and magnetostrictive according to the measurement principle.

The noise sensor is built into a sound-sensitive capacitive electret microphone. The electret face is opposite to the back electrode, and there is a very small air gap in the middle to form an air gap and an electret as the insulating medium. The metal layer on the electrode and the electret constitutes a plate capacitor as two electrodes. There is an output electrode between the two poles of the capacitor. Due to the free charge distributed on the electret film. When the acoustic wave causes the electret film to vibrate and shifts; the distance between the two pole plates of the capacitor is changed, causing the capacitance of the capacitor to change. Since the number of charges on the electret is always constant, according to the formula: Q = CU When C changes, it will inevitably cause a change in the voltage U across the capacitor, thereby outputting an electrical signal, and realizing the conversion of the sound signal to the electrical signal. Specifically, the total charge amount of the electret is constant. When the plate retreats under the sonic pressure, the capacitance decreases, and the voltage between the two poles of the capacitor increases inversely. On the contrary, the capacitance increases. The voltage between them will decrease inversely. Then, the voltage across the capacitor is taken out by the field effect with very high impedance, and amplified at the same time, so that the voltage corresponding to the sound can be obtained. Since the FET is an active device, it requires a certain bias and current to operate in an amplified state. Therefore, the electret microphone must be added with a DC bias to operate.

As we all know, the emergence of sensors has greatly changed our lives, and the convenience created for everyone's life is also comprehensive. From heat-sensitive components, light-sensitive components, gas-sensitive components to acoustic-sensitive components, etc., it has been seen how great the powerful and magical sensors are. Just like a device equipped with a sound-sensitive component, it can react with our language. Does it feel quite fun? At the moment, the technology of sensors is constantly improving innovation, but the variety, complexity and power, so that many people know very little about the sensor, not to mention its scope of application.

1. The application of sound sensor in the military

Sound sensors have been widely used in ground sensor reconnaissance monitoring systems, and their great advantage is their strong resolution. If the target is a person, not only can the voice be heard directly, but also the nationality, identity, and conversation content can be ascertained according to the voice; if the target is a vehicle, the vehicle type can be judged based on the sound. For example, a device called "audio buoy" that can be hung on a tree used by the US Army detects a distance of 300 to 400 meters, which is close to the human hearing range.

2. The application of sound sensor in medical treatment

The fiber-optic microphone has a natural anti-interference ability to the magnetic field and can be applied to the communication of magnetic resonance imaging. It is a microphone that can communicate between the patient and the doctor during the MRI scan.

3. The application of sound sensor in life

Acoustic Intrusion Detector: In addition to the portal control that can be used for the portal, it can also be used to monitor the area where an intruder appears. The outstanding advantage is that it can be used to identify the cause of the alarm. In addition, sound sensors are involved in car anti-theft and aerial detection, and the sound sensor's improvement on the sonar system also contributes. A wide variety of voice-activated switches also shine. Japan has developed a voice-activated TV that can store two people's voice commands, including booting, switching channels, changing colors, and turning off, all of which can be controlled with voice commands.

4. Sound sensor in industrial applications

The acoustic wave sensor uses the positive and negative piezoelectric effect of the lead zirconate titanate PZT piezoelectric ceramic to convert between electric energy and mechanical energy. When an electric signal is applied to the piezoelectric ceramic, mechanical vibration is generated to emit ultrasonic waves, and the ultrasonic wave propagates in the air. When the obstacle is immediately reflected back on the way, when it acts on its ceramic, there will be an electrical signal output, and the distance between the vehicle and the obstacle is calculated by the data processing time difference ranging. This kind of sensor is used as a car reversing anti-collision alarm device; most of the sewing equipment manufacturers have used the electronic detection instrument to test the sound where the machine is the source of the loud sound source, and measure the force and vibration of the parts.