AAC (Advanced Audio Coding) An encoding format that is of higher quality and broader frequency ranges than MP3. Used by iTunes to encode music.

Analog sound (See Sound Reproduction.)

Bandwidth The amount of data that can be transferred in a given period, as in bits per second (bps).

Blog (short for weblog) A Web site on which groups or individuals regularly post opinions, diaries, and/or actual information. In an audioblog, most of the content is spoken. A videoblog (or vlog) is mainly video.

Bit The most basic unit of information. Bits are either “on” or “off” and represented by a one (on) or a zero (off). (See Byte)

Bit rate How many bits can be transmitted in a second. The more bits an audio file has, the higher the quality. Music MP3s may have a bit rate of 128 Kbps (kilobits per second), a podcast might only have half that. (FM radio sound is the equivalent of 64 Kbps.)

Byte A set of 8 bits.

Codec (compressor/decompressor) A set of rules that converts data from analog to digital and back. (See Compression.)

Compression Reducing the size of a file by taking out some of the information. With audio files, this mostly means frequencies that humans cannot hear. (See lossy.)

DAP Digital audio player.

Digital sound (See Sound Reproduction.)

DRM (Digital rights management) Technology used to restrict the use/resale of music or other digital content.

Feeds Lists of podcasts and descriptions of their contents. (See RSS and Podcatchers.)

Formats Digital files of all kinds are stored in formats, such as MP3, txt, or QuickTime.

Frequency The rate at which a sound vibrates. It is stated in cycles per second (Hertz, or Hz).

GB Gigabyte, one billion bytes.

Kbps Thousands of bits per second.


Lossless compression Keeps all the original data (e.g., zip files, tiff photos).

Lossy compression Throws out some of the original data (e.g., MP3 music, jpeg photos).

MB Megabyte, one million bytes.

MP3 (MPEG-1 audio layer 3) A lossy audio-compression format that can reduce a file to as little as one-tenth of its original size.

MPEG-4 Audio and video coding standards for broadcast television, streaming audio, and other mediums.

Narrowcasting The distribution of very specific content, e.g., New Zealand nature sounds.

Podcatchers Sites that list podcasts and their content, such as Podcast Alley or PodOmatic.

Protocol Rules that describe how data is transmitted between computers.

RSS (Really Simple Syndication or Rich Site Summary) The most popular type of feed.

Sampling When an analog signal is converted to digital, it is measured at precise intervals and encoded as numbers. For example, music for CDs is sampled at 44,100 times a second.

Sound Reproduction Microphones convert changes in air pressure into variations in electrical voltage or current so they can be recorded or transmitted. These analog signals are turned back into variations in air pressure produced by loudspeakers, telephone receivers, or other means. Digital recording invoves converting analog signals into thousands of numbers per second, ensuring absolute accuracy and making it possible to store a large amount of information in a relatively small space. Digital signals must be turned back into analog signals to be played through a speaker.

Speedcast A podcast with faster speech but without a higher pitch.

Tag A word or phrase used to identify a digital file and make it easier to find on-line. For example, a podcast about the Acropolis might be tagged Athens, Parthenon, architecture, and real old buildings.

A small flash-memory podcast player
Small flash-memory MP3/podcast player (self-knotting cord is standard equipment)