1. The recording and reproduction of sound: When the children listened to the audio, they could hear their parents talking about Christmas!
2. The part of television or movie equipment that has to do with sound: The audio for making films is not the same as the visual portion (video) that is also part of a film.
3. The broadcasting, reception, or reproduction of sound: The elements related to audio are especially important in high-fidelity reproduction.
4. A sound signal: We lost the audio during the radio broadcast.

The part of any wave or signal whose frequencies are within the audible range: Sandy wondered if the audio components were strong enough for her to receive the program she wanted to listen to.

Any of a wide variety of computer components that accept or produce sound: The audio device Jenny had on her computer was important for her to receive some very nice radio music!

A sound frequency between 20 and 20,000 cycles per second, or hertz: Audio frequency refers to the frequency of oscillation able to be detected by the ear of a human.

Audio-frequencies are those of electrical, sound, or other wave vibrations coming within the range of normal human hearing.

Computer output in the form of simulated or recorded spoken words: The sound coming from the audio output was muffled and so Jack had to find a specialist to repair his device.

A small flat case containing magnetic tape on two reels, used to record and play back sound and video material: "Very few people are using audiocassettes these days since the introduction of such music sources as Apple i-Tunes and other places that provide on-line music."

Any of various instruments used to measure the frequencies of sound waves that are audible to the human ear: Linda learned in her engineering class that one type of audio-frequency meters was a resonant-reed frequency meter.

The portion of the acoustic energy spectrum: The audio-frequency range is from about 20 to 20,000 vibrations per second, or that which can be detected by a human with normal hearing:

A reference to the reproduction and transmission of sound stored in a digital format.

This includes CDs as well as any sound files stored on a computer. In contrast, the telephone system (but not ISDN) is based on an analog representation (system that represents changing values as continuously variable physical quantities) of sound.

In sound recording and reproduction systems, digital audio refers to a digital representation of the audio waveform for processing, storage or transmission. When analog sound waves are stored in digital form, each digital audio file can be decomposed into a series of samples.