Audio technology

Audio technology covers the capture, processing, storage and reproduction of sound as electrical or digital signals. Sound itself is a pressure wave in air, and a microphone converts that wave into a varying voltage, an electrical analogue of the original. A loudspeaker reverses the process, turning an electrical signal back into air movement. Between the two lie the many stages of an audio system: preamplifiers, mixers, equalisers, power amplifiers and the cabling that connects them, each meant to convey the signal with as little distortion and added noise as possible.

Quantities in audio are often expressed in decibels, a logarithmic measure that suits the wide range of levels the ear handles and roughly matches how loudness is perceived. Related figures such as dBm and dBV reference the decibel to fixed power or voltage levels, while signal-to-noise ratio (SNR) describes how far a wanted signal sits above the background noise. Other practical concerns include frequency response, dynamic range, and forms of degradation such as hum, distortion and, in digital systems, jitter.

Modern audio is largely digital. An analogue signal is sampled and quantised into numbers that can be stored and processed without further loss, manipulated by digital signal processing (DSP), and compressed for storage or transmission. Lossy schemes such as MP3 discard sound the ear is unlikely to notice to save space, while multichannel systems such as Dolby Digital (AC-3) and Dolby Pro Logic distribute sound across several loudspeakers for surround reproduction. Acoustics, including room behaviour and loudspeaker placement, shapes the final result as much as the electronics do.

Frequently asked questions

Why are decibels used in audio?

The decibel is a logarithmic ratio that compresses the very wide range of audio levels into manageable numbers and corresponds reasonably well to how the ear perceives loudness.

What does signal-to-noise ratio tell you?

It indicates how much stronger the wanted audio signal is than the underlying noise; a higher ratio means a cleaner, quieter background.

How does MP3 reduce file size?

MP3 is a lossy format that removes audio detail the ear is unlikely to detect, shrinking the data while keeping the sound acceptable to most listeners.