The sound is amazing. All the different noises we hear are caused by the tiny pressure difference in the air around us. Surprisingly, air transmits these pressure changes over a relatively long distance and is so accurate.
If you have read the working principle of CD, you will know the first microphone. It is a metal septum attached to a needle, and this needle has a pattern on a piece of metal foil. When someone speaks to the diaphragm, the pressure difference in the air moves the diaphragm, the diaphragm moves the needle, and then it is recorded on the foil. When the needle comes back to the foil later, the vibration of scratching on the foil will move the diaphragm and regenerate the sound. The working principle of this purely mechanical system indicates how much energy can be generated by vibration in the air.
All modern microphones try to accomplish the same things as the original, but do so electronically rather than mechanically. The microphone hopes to take different pressure waves in the air and convert them into different electrical signals. Several different techniques are usually used to accomplish this conversion. Check out the next page to learn more about different types of microphones-including the first one invented by Alexander Graham Bell.
10. Liquid microphone
The liquid microphones invented by Alexander Graham Bell and Thomas Watson were among the first microphones developed, and they were the pioneers of condenser microphones. Early liquid microphones used metal cups filled with water and sulfuric acid. Place the septum on the cup with a needle on the receiving side of the septum. Sound waves cause the needle to move in the water. A small amount of electric current flows to the needle, which is modulated by sound vibration. The liquid microphone has never been a particularly useful device, but it is a great scientific experiment.
9. Carbon microphone
The oldest and simplest microphone uses toner. This was the technology used in the first phones and is still used in some phones today. The toner has a thin metal or plastic film on one side. When sound waves hit the diaphragm, they compress the carbon dust, thereby changing its resistance. By passing current through the carbon, the change in resistance changes the amount of current that flows.
8. Fiber optic microphone
Fiber optic systems use ultra-thin glass bundles to transmit information instead of traditional metal wires, and in recent years have revolutionized the field of telecommunications, including microphone technology. What's the big deal? Unlike traditional microphones, which are usually large and send electrical signals, fiber optic microphones can be very small, and they can be used in electrically sensitive environments. They can also be produced without metal, which makes them very useful in magnetic resonance imaging (MRI) applications and other radio frequency interference issues.
7. Dynamic microphone
Dynamic microphones use electromagnetic effects. When the magnet moves over the wire (or wire coil), the magnet induces current to flow in the wire. In a dynamic microphone, when sound waves hit the diaphragm, the diaphragm moves the magnet or coil, and the movement generates a small current.
6. Electret microphone
The electret microphone is one of the most widely used microphones on the planet. Because they are cheap and relatively simple, electret microphones are used in cell phones, computers, and hands-free headsets. An electret microphone is a condenser microphone in which the external charge is replaced by an electret material, which by definition is in a state of permanent electrical polarization.
5. Ribbon microphone with ribbon
In ribbon microphones, a thin ribbon-usually aluminum, duralumin or nano-film-is suspended in a magnetic field. The sound waves move the ribbon, thereby changing the current flowing through it. Ribbon microphones are bidirectional, which means they pick up sound from both sides of the microphone.
RCA PB-31 is one of the earliest ribbon microphones. It was produced in 1931 and changed the audio and broadcasting industries because it set new standards when it was clear. Several other microphone manufacturers have also made comparable models, including BBC-Marconi Type A and ST&C Coles 4038.
4. Laser microphone
The working principle of the laser microphone is to capture the vibration under the aircraft, such as window glass, for example, and send the signal feedback to a photodetector, which reflects the laser beam and converts it into an audio signal. When sound hits the window glass, it will bend and bend the laser beam, which can be converted into sound using a photoelectric tube. In recent years, scientists have been developing a new type of laser microphone that works by passing smoke through a laser beam, which is aimed at a photocell and then converted into an audio signal.
3. Condenser condenser microphone
Condenser microphones are essentially capacitors, and one plate of the capacitor moves in response to sound waves. This movement changes the capacitance of the capacitor, and these changes are amplified to produce a measurable signal. Condenser microphones usually require a small battery to provide voltage to the capacitor.
2. Cardioid microphone
If you want to record sound in front of and on the side of the microphone-but not behind it-a cardioid microphone is for you. The polar coordinate of the cardioid gain is cardioid (hence the name), and the highest sensitivity is directly in front of the microphone, slightly less on the side. Therefore, cardioid microphones are very suitable for recording live performances without excessive crowd noise. Many handheld microphones used to amplify human voices are cardioid microphones.
1. Crystal microphone
Certain crystals change their electrical properties when they change shape (see an example of how a quartz watch works). By connecting the diaphragm to the crystal, when sound waves hit the diaphragm, the crystal will generate a signal.
As you can see, almost all imaginable technologies are used to convert sound waves into electrical signals. One of the most common things is the diaphragm, which collects sound waves and generates movement through any technique used to generate signals.