What is a Microphone?

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A microphone is a device that converts sound vibrations in the air into electronic signals and records them to a medium or transmits them over a loudspeaker. Microphones are used in many types of audio recording devices for purposes including communications, music vocals, speech, and sound recording.

Microphones can be standalone or built into devices such as headsets and telephones.

The History of Microphones

The following is the timeline of microphone evolution −

• 5th Century BC (Greece) − The earliest devices to amplify the human voice were acoustic megaphones. These included theater masks with horn-shaped mouth openings used to acoustically amplify the voice of actors in amphitheaters.
• 1665 (England) − Robert Hooke, an English physicist, experimented with the "lovers' telephone" made of stretched wire with a cup attached at each end, marking an early exploration into the medium of sound transmission beyond air.
• 1856 (Italy) − Antonio Meucci, an Italian inventor, developed a dynamic microphone that generated electric current by moving a coil of wire through a magnetic field. This method of modulation would later influence telephone technology.
• 1857 (Italy) − Meucci described his device, which used a vibrating diaphragm and an electrified magnet with a spiral wire. The diaphragm’s movement altered the current, creating vibrations that were transmitted to a receiving diaphragm, reproducing the sound.
• 1861 (Germany) − Johann Philipp Reis, a German inventor, built the "Reis telephone," an early sound transmitter using a metallic strip attached to a vibrating membrane, producing intermittent current.
• 1876 (USA) − Alexander Graham Bell and Elisha Gray achieved better results with the "liquid transmitter" design in early telephones. This system used a diaphragm attached to a conductive rod in an acid solution but produced poor sound quality.
• 1870s (England/USA) − David Edward Hughes invented the carbon microphone, independently developed by Hughes, Emile Berliner, and Thomas Edison. Although Edison was awarded the patent, Hughes is credited by historians for demonstrating the device earlier. This microphone was critical to the development of telephony, broadcasting, and the recording industries.
• 1886 (USA) − Thomas Edison refined the carbon microphone into the carbon-button transmitter, which was used during the first radio broadcast at the New York Metropolitan Opera House in 1910.
• 1916 (USA) − C. Wente of Western Electric developed the first condenser microphone, marking a significant breakthrough in microphone technology.
• 1923 (UK) − The first practical moving coil microphone, the Marconi-Sykes magnetophone, was developed by Captain H. J. Round and became the standard for BBC studios in London.
• 1930 (UK) − Alan Blumlein and Herbert Holman released the HB1A moving coil microphone, which became the best standard of the day.
• 1923 (USA) − The ribbon microphone was introduced, an electromagnetic type developed by Harry F. Olson. RCA advanced the development of this microphone, improving its directionality and making it a key tool in television and film production.
• 1963 (USA) − Electro-Voice developed the shotgun microphone, which won an Academy Award for its advancements in microphone pattern control and directionality.
• Late 20th Century (USA) − The Shure Brothers released the SM58 and SM57, both of which became highly popular microphones due to their reliability and sound quality.

How Do Microphones Work?

The most common type of microphone, the dynamic microphone, utilizes a coil suspended in a magnetic field, which can be attached to multiple membranes for extended frequency response.

Dynamic microphones use electrical energy through induction to generate the audio signal. These microphones are ideal for stage performance.

The microphone capsule contains a small diaphragm connected to a moving coil. When sound waves hit the diaphragm, it vibrates, causing the coil to move back and forth in the magnet's field, generating an electrical current.

However, how a microphone operates ultimately depends on its intended purpose.

One of the main considerations, aside from the type of device, is what is being recorded. The directionality of microphones is another important factor in microphone design.

Types of Microphones

Lets now explore a few different types of microphones based on their intended use.

1. Omnidirectional Microphones

Omnidirectional microphones are designed to record all sounds in an area but are not effective at focusing on a single subject amid background noise.

An example of an omnidirectional microphone is the Lavalier microphone, which is often used in television production.

2. Directional Microphones

Directional microphones, also called unidirectional, are better at picking up sounds from a particular direction and are useful in environments with significant background noise.

Shotgun microphones are a type of directional microphone often used in film and television production to capture audio from a distance.

Cardioid microphones are another type of directional microphone commonly used for live music recordings and performances.

3. Bidirectional Microphones

Bidirectional microphones are designed to pick up sounds from two directions, making them ideal for recording conversations.

An example of a bidirectional microphone would be those used in dictation machines.

4. Condenser Microphones

Condenser microphones use the varying electrical charge of a capacitor, with a diaphragm acting as one of the capacitor plates. The plate is biased by a fixed charge, often from a battery, which also amplifies the signal.

The capacitance varies with the diaphragms movement relative to the other plates, providing the means to record the sound into the electrical signal.

For example, electret microphones are used in cell phones and computers as a type of condenser microphone that uses a polarized ferroelectric material.

5. Laser Microphones

Laser microphones use the vibrations of surfaces affected by sound waves to capture sound from a distance. The lasers return at different angles due to the vibration, and these changes are interpreted and translated into sound waves.

Laser microphones are used in situations where sounds need to be captured from a distance.

6. Ribbon Microphones

Ribbon microphones consist of a thin strip of conductive metal suspended in a magnetic field. The ribbon is usually made from aluminum, duralumin, or nanofilm.

When sound waves hit the microphone, the ribbon vibrates, which generates an electrical signal.

Ribbon microphones are often used in studios for recording music, as they tend to produce a smooth, natural sound.

Microphones vs. Speakers

The following table shows the differences between microphone and speaker −

Evolution of Unified Communications

The development of microphone technology helped lead to the invention of the telephone and has remained integral to telephony and communications ever since.

With advancements in microphone design, many different types of microphones are available to suit various applications.

Digital microphones have become more popular in recent years due to their improved sound quality and durability. Additionally, wireless microphones are now commonly used in various settings, from live concerts to television production, though analog microphones are still widely used due to their affordability and availability.

In any case, microphones are a vital piece of technology in today's world and will continue to be important in the future.