The Pattern Playback is an early talking device that was built by Dr. Franklin S. Cooper and his colleagues, including John M. Borst and Caryl Haskins, at Haskins Laboratories in the late 1940s and completed in 1950. There were several different versions of this hardware device. Only one currently survives. The machine converts pictures of the acoustic patterns of speech in the form of a spectrogram back into sound. Using this device, Alvin Liberman, Frank Cooper, and Pierre Delattre (later joined by Katherine Safford Harris, Leigh Lisker, and others) were able to discover acoustic cues for the perception of phonetic segments (consonants and vowels). This research was fundamental to the development of modern techniques of speech synthesis, reading machines for the blind, the study of speech perception and speech recognition, and the development of the motor theory of speech perception.
To create sound, the Pattern Playback uses an arc light source which is directed against a rotating disk with 50 concentric tracks whose transparencies vary systematically in order to produce 50 harmonics of a fundamental frequency. The light is further projected against a spectrogram whose reflectance corresponds to the sound pressure level of the partial of the signal, and is then directed towards a photovoltaic cell by which the light variation is converted into sound pressure variations.
The technique of pattern playback also now refers, more generally, to algorithms or techniques for converting spectrograms, cochleagrams, and correlograms from pictures back into sounds.
Digital pattern playback 
In the 1970s, digital pattern playbacks began to supplant the earlier version. In early prototype was developed at Haskins Laboratories which combined a "Ubiquitous Spectrum Analyzer" for automatic spectral analysis, along with a VAX GT-40 display processor for graphic manipulation of the displayed spectrogram, a form of "synthesis by art", and subsequent re-synthesis using a 40 channel filter bank. This hybrid hardware/software digital pattern playback was eventually replaced at Haskins Laboratories by the HADES software system, designed by Philip Rubin, and implemented in Fortran on the VAX family of computers. A more modern version has been described by Arai and colleagues.
See also 
- Caryl Haskins
- Haskins Laboratories
- Alvin Liberman
- reading machine
- Robert Remez
- Philip Rubin
- motor theory of speech perception
- speech synthesis
Cooper, F.S., Liberman, A. M., & Borst, J. M., The interconversion of audible and visible patterns as a basis for research in the perception of speech. Proceedings of the National Academy of Science, 1951, 37, 318-325.
Cooper, Franklin S., Delattre, Pierre C., Liberman, A. M., Borst, J. M. & Gerstman, L. J., Some experiments on the perception of synthetic speech sounds. The Journal of the Acoustical Society of America, 1952, 24, 597-606.
Cooper, Franklin S., Some instrumental aids to research on speech. In Report of the fourth annual round table meeting on linguistics and language teaching. Washington, D.C.: Institute of Languages and Linguistics, Georgetown University, 1953, 46-53.
J. M. Borst, The use of spectrograms for speech analysis and synthesis, J. Audio Eng. Soc., 4, 14-23, 1956.
Liberman, Alvin M., Some results of research on speech perception. The Journal of the Acoustical Society of America, 1957, 29, 117-123.
Remez, Robert E., Adaptation of the category boundary between speech and nonspeech: A case against feature detectors. Cognitive Psychology, 1979, 11, 38-57.
Malcom Slaney. Pattern Playback from 1950 to 1995. Proceedings of the 1995 IEEE Systems, Man and Cybernetics Conference. October 22-25, 1995, Vancouver, Canada.
Malcolm Slaney, Pattern Playback in the 90's, in Advances in Neural Information Processing Systems 7, Gerald Tesauro, David Touretzky, and Todd Leen (eds.), MIT Press, Cambridge, MA, 1995.
T. Arai, K. Yasu and T. Goto, Digital pattern playback, Proc. Autumn Meet. Acoust. Soc. Jpn., 429-430, 2005.
T. Arai, K. Yasu and T. Goto, Digital pattern playback: Converting spectrograms to sound for educational purposes, Acoust. Sci. & Tech., 27(6), 393-395, 2006