Microphone

Lore & Background

The earliest devices to increase the volume of the human voice were acoustic megaphones, with examples from fifth-century-BC Greece using theater masks with horn-shaped mouth openings. Between 1664 and 1685, Robert Hooke experimented with a medium other than air, inventing an early telephone made of stretched wire with a cup at each end, now known as a tin-can telephone. In 1856, Antonio Meucci developed a dynamic microphone based on generating electric current by moving a coil of wire in a magnetic field, writing in 1857 of a vibrating diaphragm and an electrified magnet with a spiral wire. In 1861, Johann Philipp Reis built an early sound transmitter using a metallic strip attached to a vibrating membrane, and better results came in 1876 with the liquid transmitter design in early telephones from Alexander Graham Bell and Elisha Gray, though these gave poor sound quality.

The first microphone enabling proper voice telephony was the loose-contact carbon microphone, independently developed by David Hughes in England and Emile Berliner and Thomas Edison in the US. Edison was awarded the first patent in mid-1877 after a long legal dispute, but Hughes had demonstrated his working device years earlier, and most historians credit him with its invention. The Berliner microphone found commercial success through use by Alexander Graham Bell for his telephone.

Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886, employed at the first radio broadcast in 1910. In 1916, E.C. Wente developed the first condenser microphone. The first practical moving coil microphone was built in 1923, and the Marconi-Sykes magnetophone, developed by Captain H. J. Round, became the standard for BBC studios in London, improved in 1930 by Alan Blumlein and Herbert Holman with the HB1A. Also in 1923, the ribbon microphone was introduced, believed to be the work of Harry F. Olson, and RCA made large advances in pattern control.

The Neumann U 47 of 1949 was the first studio condenser microphone to use a large dual-diaphragm capsule with switchable pickup patterns and a vacuum tube amplifier. Electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. The Shure SM57 of 1965 used the Unidyne III capsule to deliver clear and distortion-free sound, with a compact and rugged design allowing close placement to drums and amplifiers.

From Sound Wave to Electrical Signal

A microphone is, at its core, a transducer — a device whose entire purpose is to translate the pressure variations of a sound wave in air into an electrical signal that machines can process, store, or transmit. This single conversion underpins an enormous range of technologies we encounter daily: telephones, hearing aids, mobile phones, broadcast studios, and recording equipment all depend on it. Beyond these familiar applications, microphones appear throughout consumer electronics broadly, making them one of the most quietly ubiquitous pieces of technology in modern life.

Three principal transducer designs dominate current use. The dynamic microphone relies on a coil of wire suspended within a magnetic field; the condenser microphone treats its vibrating diaphragm as one plate of a capacitor; and the contact microphone harnesses a crystal of piezoelectric material. Whichever principle is employed, the raw signal typically must pass through a preamplifier before it is strong enough to be recorded or played back.

Echoes in Bronze and Wire: The Ancient and Early Modern Quest

Long before electricity entered the picture, human societies grappled with the simple problem of making a voice carry across a large space. In fifth-century-BC Greece, theater masks were crafted with horn-shaped mouth openings that acoustically amplified an actor's voice so it could fill an amphitheater. Centuries later, between 1664 and 1685, the English physicist Robert Hooke experimented with a medium other than air for transmitting sound, building a device of stretched wire with a cup at each end — what we now recognize as the tin-can telephone. The nineteenth century brought the first true electrical attempts.

In 1856, Italian inventor Antonio Meucci constructed a dynamic microphone that generated current by moving a coil of wire through a magnetic field, a modulation method that would prove foundational to telephone technology. In 1861, German inventor Johann Philipp Reis built a transmitter using a metallic strip on a vibrating membrane to produce intermittent current. By 1876, Alexander Graham Bell and Elisha Gray had refined the concept with a liquid transmitter — a diaphragm attached to a conductive rod dipped in acid — though the sound quality remained disappointingly poor.

The Carbon Microphone and the Birth of Telephony

The breakthrough that finally made voice telephony practical was the loose-contact carbon microphone, developed independently by David Hughes in England and by Emile Berliner and Thomas Edison in the United States. Edison received the first patent in mid-1877 after a prolonged legal dispute, yet Hughes had already demonstrated his working device before numerous witnesses several years earlier, and most historians credit him as the true inventor. Berliner's version found commercial traction when Alexander Graham Bell adopted it for his telephone, and Berliner subsequently joined Bell's employ.

The carbon microphone proved critical to the growth of telephony, broadcasting, and the recording industries. Edison later refined the design into his carbon-button transmitter of 1886, a device so effective that it was used for the very first radio broadcast — a performance at the New York Metropolitan Opera House in 1910. This single component, a simple arrangement of carbon granules whose resistance changed with sound pressure, became the backbone of an entire global communications infrastructure.

Studio Revolution: From Condenser Capsules to the SM57

The twentieth century saw a rapid succession of microphone designs that transformed recording and broadcasting. In 1916, E. C. Wente at Western Electric created the first condenser microphone, a design that would eventually become the go-to choice in laboratories and recording studios due to its exceptionally light diaphragm mass. In 1923, the first practical moving-coil microphone was built, and Captain H. J. Round's Marconi-Sykes magnetophone became the standard in BBC London studios. That same year, the ribbon microphone appeared, believed to be the work of Harry F. Olson, who adapted the principle of a ribbon speaker to microphone construction.

RCA later made major advances in pattern control, giving ribbon mics true directionality. The Neumann U 47 of 1949 marked a turning point: the first studio condenser with a large dual-diaphragm capsule, switchable pickup patterns, and a vacuum-tube amplifier, setting a new benchmark for warm, detailed vocal and instrument capture. As television and film demanded greater fidelity, Electro-Voice answered with their Academy Award-winning shotgun microphone in 1963, and Shure followed in 1965 with the SM57 — a compact, rugged dynamic mic whose Unidyne III capsule delivered clear, distortion-free sound close to drums and amplifiers, going on to become one of the best-selling microphones ever made.

Reader's Guide

Microphones are categorized by their transducer principle (condenser, dynamic, etc.) and by their directional characteristics (omni, cardioid, etc.). The condenser microphone, also called a capacitor or electrostatic microphone, was invented at Western Electric in 1916 by E. C. Wente. Its diaphragm acts as one plate of a capacitor, and audio vibrations produce changes in capacitance.

Condenser microphones span from telephone mouthpieces to high-fidelity recording microphones, generally producing high-quality audio due to the very small mass moved by the sound wave. They require a power source, provided as phantom power or from a small battery. Some condenser microphones have two diaphragms that can be electrically connected to provide a range of polar patterns, such as cardioid, omnidirectional, and figure-eight, and some allow continuous pattern variation. There are two main categories: DC-biased microphones and radio frequency (RF) or high frequency (HF) condenser microphones.

In DC-biased condenser microphones, the plates are biased with a fixed charge, and the voltage across the capacitor changes with vibrations. The capacitance of the capsule (around 5 to 100 pF) and the value of the bias resistor (100 MΩ to tens of GΩ) form a filter that is high-pass for the audio signal and low-pass for the bias voltage. The Shure SM57 of 1965 revolutionized the recording of instruments and amplified live music, becoming one of the top selling microphones in history.