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What Is a Digital Microphone?

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  • Written By: Mal Baxter
  • Edited By: Daniel Lindley
  • Last Modified Date: 04 December 2016
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A digital microphone is a device for picking up analog sound waves and converting them into electronic signals through the use of digital technology. Where conventional microphones operate on a principle of electronic processing of voltage differences caused by sound vibration against metal surfaces, digital microphones use dielectric wafers or thin film transducers to capture sound. This permits small construction, effective immunity to noise, and more precise sound reproduction. Digital microphones appear in low-grade and high-end applications, including toys, computers, telephones, and sound studios.

One large market for digital microphone technology is the mobile telephone industry, as this technology offers a number of strengths, like noise cancellation, low power consumption, and low production costs. The technology is typically found in computers and tablets as well as in conventional microphone designs. Desktop microphones sit on a stand and are used for conference calls or dictation. Headset microphones are often used for gaming or chatting online. Studio microphones enable quality recording for music, podcasts, or professional voice recording.

Most digital microphone technologies work by converting analog audio sound waves to digital signals. Essentially, a digital sensor receives wave vibrations and translates them into electronic signals. It does this by slicing a wave into a series of digital values that can be easily processed, filtered, or reworked for effect. Microphones connect via cables with jacks or universal serial bus (USB) ports.

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Micro-electro-mechanical systems (MEMS) transducers use thin film to detect capacitance changes caused by sound. Complementary metal-oxide-semiconductor (CMOS) wafers employ metal-dielectric structures etched into a diaphragm, functioning like a digital eardrum. Both methods digitize signals and permit a multitude of processing options.

Digital Analog Converters (DACs) are chips found in sound cards, players, or speakers. These transform digital data back into the voltage, current, or electric charge of an analog signal. Speakers work on similar principles as microphones, but in reverse.

MEMS devices use a silicon pressure-sensing diaphragm etched into silicon. While easy to produce, these components have narrower bandwidths, and are costlier and more fragile than those in electret condenser microphones (ECM). MEMS components often employ a tried-and-true junction gate field-effect transistor (JFET). This transistor impedes and regulates electric current, and functions as the microphone's preamp, a component that boosts its output signal from the minute sound waves of analog input: for example, a voice.

CMOS innovations offer a number of advantages over MEMS diaphragms. These can include reduced harmonic distortion, improved gain settings, and direct digital output. With such technical distinctions, it becomes clear that a microphone is not necessarily a true digital microphone just because it has a digital display.

As the development of digital microphone technology has continued, prices have fallen and quality products have become more available. Microphones become more capable of capturing true sound without extraneous noise or inconsistencies. Digitization affords users of all skill levels many creative options. Portable devices function better in noisy environments, and users develop more professional-grade media at consumer prices.

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