A microphone converts sound waves into electrical signals through various transduction methods. This essential audio device serves as the foundation of modern sound recording and amplification technology.
Historical Development
The journey of microphone technology began in ancient Greece with acoustic megaphones. In 1876, Alexander Graham Bell and Elisha Gray made breakthrough advances with their “liquid transmitter” design. The first practical microphone emerged when David Edward Hughes developed the carbon microphone, which Thomas Edison later refined into his carbon-button transmitter in 1886.
Core Technologies
Dynamic Microphones
The dynamic microphone uses electromagnetic induction with a moving coil attached to a diaphragm. When sound waves hit the diaphragm, the coil moves within a magnetic field, generating an electrical current. The Shure SM58, introduced in the late 20th century, exemplifies this robust technology.
Condenser Microphones
E.C. Wente invented the condenser microphone at Western Electric in 1916. These microphones use a thin metal diaphragm and a fixed metal plate to form a capacitor. Sound waves cause the diaphragm to vibrate, changing the capacitance and creating an electrical signal.
Ribbon Microphones
Ribbon microphones employ a thin metal ribbon suspended in a magnetic field. The ribbon responds to air velocity rather than sound pressure, producing a distinctive bi-directional pickup pattern. RCA pioneered significant advances in this technology.
Modern Applications
Professional Audio
Recording studios and concert venues rely heavily on high-fidelity condenser and dynamic microphones. These environments demand precise sound capture and reliable performance.
Consumer Electronics
Modern devices incorporate MEMS microphones – tiny silicon-based sensors that integrate directly with digital circuits. These power billions of smartphones and computers worldwide.
Specialized Uses
Fiber-optic microphones serve in unique environments like MRI facilities, where conventional microphones would fail. Laser microphones enable long-distance sound capture through window vibrations.
Technical Characteristics
Polar Patterns
Microphones exhibit distinct directional sensitivities:
- Cardioid: Heart-shaped pattern, ideal for vocal performance
- Omnidirectional: Equal sensitivity in all directions
- Figure-8: Bi-directional pickup, common in ribbon microphones
Power Requirements
Condenser microphones need external power, typically supplied as phantom power through the microphone cable. Dynamic and ribbon microphones operate without external power, making them more suitable for live performance environments.
The evolution of microphone technology continues to shape how we capture and transmit sound, from the simplest telephone call to the most sophisticated recording studio setup.
A microphone, colloquially called a mic (/maɪk/), or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones, for recording sounds, speech recognition, VoIP, and other purposes, such as ultrasonic sensors or knock sensors.
Several types of microphone are used today, which employ different methods to convert the air pressure variations of a sound wave to an electrical signal. The most common are the dynamic microphone, which uses a coil of wire suspended in a magnetic field; the condenser microphone, which uses the vibrating diaphragm as a capacitor plate; and the contact microphone, which uses a crystal of piezoelectric material. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced.