How does a microphone capture sound? Simple explanation

15 Tem 21:24

The classic way dynamic mics work is this: a thin diaphragm picks up tiny vibrations in air pressure, and it's connected to a coil behind a fixed magnet. When the coil moves back and forth in the magnet's magnetic field, a tiny voltage is generated thanks to Faraday's law—that's the signal. In condenser (capacitor) models, the distance between the diaphragm and a fixed plate changes, and the change in capacitance produces a voltage. If it sounds slow to you, it's because pressure waves in the air are actually moving super slowly; I remember seeing this on an oscilloscope during my internship and thinking, "Is this really what sound looks like?"

15 Tem 22:56

As we all know, there's a flexible diaphragm behind microphones, just like our eardrums. When sound waves travel through the air and hit the microphone's diaphragm, it starts to vibrate. For example, in my old XM8 model, this diaphragm was made of a super thin material, almost as sensitive as a strand of hair. The vibrations are converted into electricity through an electromagnetic principle: most microphones have a coil wrapped around a fixed magnet. The diaphragm's vibration moves this coil, changing the magnetic field, and ultimately producing a weak electrical signal. So, it's actually the combination of the diaphragm that "hears" the sound and the magnetic system that converts it into electricity that does the job. The same principle applies to an old Shure SM58, it just captures the sound in a slightly more "robotic" tone—I love that sound when listening to recordings from the 60s.

16 Tem 01:12

You can actually compare a microphone's diaphragm to an electric analog clock. The thin membrane (diaphragm) of the microphone vibrates when exposed to pressure changes from sound waves, much like the pendulum of a clock moving back and forth to drive the hour and minute hands. These vibrations activate the magnet system (coils and magnets) behind the diaphragm — as the coil moves within the magnetic field, an electric current is generated. Similarly, the working principle of a simple speaker is the exact opposite: there, an electric signal is converted into vibration, whereas here, vibration is converted into a signal. As for the process of converting to digital data, you can compare it to a simple digital camera. The microphone's weak analog signal (just as the sensor detects light) is first amplified by the sound card, and then, through the ADC (Analog-to-Digital Converter), this continuous waveform data is converted into binary code of 1s and 0s that the computer can understand. Ultimately, when you record a 'hello' from your throat in digital form, you're actually converting it into a sequence of numbers.

16 Tem 03:01

Hah, I was also researching "how does a notebook capture microphone sound" when I was buying a new notebook, and I thought to myself "oh yeah, it's the diaphragm, right?" 😅

16 Tem 05:01

Sound wave to electrical signal conversion systems may seem deceptively simple at first glance, but they're actually deeply rooted in physics. In short, a microphone contains a thin, vibrating component called a *diaphragm*. When exposed to sound waves, this diaphragm vibrates much like the skin of a drum. If you're wondering, "How exactly does it vibrate, professor?"—remember from physics class: sound waves compress and rarefy the air, creating pressure changes that cause air molecules to strike the diaphragm, making it vibrate. Behind the diaphragm lies an electrical mechanism. In dynamic microphones—the most common type—a thin wire loop (a coil) is suspended within the magnetic field of a circular magnet placed just behind the diaphragm. As the diaphragm vibrates, the coil moves with it, sliding back and forth within the magnetic field. According to the principle of electromagnetic induction, a current is generated in a conductor moving through a magnetic field—and that current is the moment the sound is converted into an electrical signal. In condenser microphones, static electricity comes into play: the diaphragm is a thin metal layer, paired with a fixed plate nearby, with a voltage applied between them. When sound pressure causes the diaphragm to vibrate, the distance between the plates changes, producing a signal proportional to the change in capacitance. The next step is that this analog signal continues to fluctuate, but to be understood by digital equipment, it passes through a circuit called an ADC (Analog-to-Digital Converter). The ADC samples the continuously changing signal at regular intervals and converts it into digital values (such as 16-bit or 24-bit), turning it into data that can be processed by speakers or computers. So in essence, a microphone is like a *detector of air vibrations*. It converts pressure changes in the air first into electrical current via the laws of physics, and then into digital data—truly a collaboration of physics and electronics.