A microphone is an electronic appliance that converts sound waves into electrical signals in order to record audio. This signal can then be amplified or transformed into a digital signal, which can then be interpreted with the help of a computer or any other digital audio system. So, how does a microphone work?
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Microphones work as transducers, that are devices that are used to convert energy from one form to another. They convert sound waves into audio signals. In other words, the mechanical energy produced by an object is converted into electrical energy.
Let’s break this down a bit. The modern microphone has seven components: a windscreen, diaphragm, coil, capsule, magnetic core, body, and output.
Sound waves are generated by our voices when we speak. These bring energy into the microphone as we talk. The sound that we hear is energy carried by vibrations in the air.
The diaphragm is a microscopic membrane that functions similarly to human eardrums. When sound hits the microphone, it passes through the diaphragm and causes the vibration. And this vibration is later converted into an electric signal. As sound travels through the diaphragm, it causes the coil to vibrate.
The coil will vibrate between two magnets. A magnetic field is generated by the permanent magnet, which cuts through the coil. An electric current travels through the coil as it passes back and forth through the magnetic field. The microphone sends an electric current to an amplifier or sound recording unit. And that is how a microphone works.
What are the types of microphones?
Microphones come in a variety of shapes and sizes, and although their basic function (to convert sound waves into electricity) is the same, they do it in slightly different ways. What we just described is known as the dynamic microphone which is also the most popular microphone. They are basic in nature, consisting of a magnet wrapped in a metal coil.
On the front end of the magnet, a thin layer called a diaphragm transmits vibrations from sound waves to the coil. The sounds are then transferred to electrical wires, which then transmit the sound as an electrical signal. Dynamic microphones are usually very robust and do not require electrical power due to their simple nature.
Another kind of microphone is the ribbon microphone. The fidelity of ribbon microphones is well established. A thin ribbon of aluminum, duralumin, or nanofilm is suspended in a magnetic field in these devices. The ribbon vibrates as a result of incoming sound waves, producing a speed of the vibration that is proportional to the voltage. An electrical signal is used to relay this voltage.
Modern ribbon microphones have replaced the magnets with stronger ones that provide better signal – in some cases even stronger than dynamic microphones – while early ribbon microphones needed a transformer to increase the output voltage. Despite the fact that condensers have increasingly replaced ribbon mics, some models are still manufactured and used today.
The condensers are widely used for audio recording. Their sensitivity and flat frequency response are well-known. A front plate (the diaphragm) and a backplate that is parallel to the front plate are used in any condenser microphone. The diaphragm vibrates as sound waves strike it, changing the distance between the two surfaces.
An electrical signal is used to communicate this transition. Condensers, unlike dynamic microphones, require electricity to operate. This current can come from an internal battery, but it’s more likely to come from a 48-volt “phantom power” source like a preamp or mixing console.
How is a microphone designed?
A diaphragm of thin plastic is connected to a coil of voice in a dynamic or moving-coil microphone. The voice coil is made up of several turns of wire of copper that is insulated with a bobbin of small diameter wound.
A magnet that is permanent surrounds the speech coil. The diaphragm vibrates in response to sound, causing the voice coil to rotate on its axis.
And this movement causes a voltage to be generated in the coil, and the audio signal is this induced current.
Two plates of metal are slightly spaced apart in a condenser or capacitor microphone, and both of these plates work together to form a capacitor. To let you know, an electrical charge-storage device is known as capacitor. A diaphragm is formed by the front plate. An electric current is generated in the wires that are attached as the diaphragm vibrates, generating an electric signal among the two surfaces.
A ribbon microphone’s diaphragm is made of a thin ribbon of corrugated aluminum that is about 2-inch long and 0.5-inch thick and is suspended through a strong field of magnet. The ribbon slices through the magnetic field when sound pressure changes displace it.
What is the origin of the microphone?
In the year 1876, Alexander Graham Bell invented the first microphone as a telephone transmitter. It was a liquid unit that was inconvenient to use. The first practical carbon microphone was invented by Thomas Alva Edison in 1886. Carbon microphones were widely used in radio transmissions and telephone transmitters until they were replaced by piezoelectric ceramic components in the 1970s.
The carbon microphone’s frequency range was small, so it couldn’t effectively replicate music. E. C. Wente of Bell Laboratories invented the condenser microphone in 1916. To pick up the subtle signals, the condenser microphone needed an amplifier built into the microphone. Radio broadcasting and the first generation of sound motion pictures have used condenser microphones.
In 1931, Wente and A. C. invented the dynamic microphone which is known as one of the most significant event of modern science and technology of microphones. In a way, it reshaped the world of modern microphones.
While we use microphones every day, we seldom take the time to wonder how they came to be, and how they function. We hope this article helped solve the mystery of how microphones work, even if just a little bit.