ARPABET

ARPABET is a phonetic transcription code developed by the Advanced Research Projects Agency (ARPA), a U.S. Department of Defense agency, and later used by the Speech Assessment and Recognition (SAR) project. It represents English phonemes using a string of characters, typically ASCII.

ARPABET assigns a unique symbol to each distinct sound (phoneme) in American English. Unlike standard English orthography, which can have multiple pronunciations for the same letter (e.g., the "a" in "cat" and "father"), ARPABET aims for a one-to-one correspondence between symbol and sound. This makes it useful for speech synthesis, speech recognition, and other computational linguistics applications.

The ARPABET character set includes letters, numbers, and punctuation marks. Many of the symbols correspond directly to IPA (International Phonetic Alphabet) symbols or English alphabet letters representing similar sounds. For sounds not easily represented by existing characters, ARPABET utilizes numerical suffixes and punctuation to create distinct symbols.

While ARPABET was originally intended for representing American English, its principles can be adapted to other languages as well, although different phonetic transcription systems specific to those languages may be more appropriate. The core goal remains consistent: to provide a unambiguous and machine-readable representation of pronunciation. The system is often used in conjunction with pronunciation dictionaries for text-to-speech (TTS) systems.