Software Emulation of a Hardware Voice Synthesiser


The aim of this project was to develop a fully functional emulator of the Speech Plus CallText 5010 hardware voice synthesiser used by Professor Stephen Hawking. Successful completion of the project would allow him to preserve his voice and would greatly reduce the complexity of the communication system he had been using. There were only two fully working hardware boards in existence, and these were already showing major signs of wear. The goal was to retain the exact characteristics of the voice and all the functionality of the original board. It was achieved by reverse engineering the Digital Signal Processor chip present on it, developing an emulator of the chip and merging it with an already existing custom-made CPU (Central Processing Unit) emulator. The operation of both emulators was carefully verified and validated at all stages of development by comparing it with hardware and making sure that the results are bit-perfect. The origin of the project dates back to 2010 and the final result is a collective effort by a number of people. There have been numerous attempts to copy the behaviour of the synthesiser in the past; however, the emulator created as a part of this project was accepted for use by Professor Hawking. More technical details of the project and audio samples can be found at


voice synthesiser, software emulator, engineering, electronics, Stephen Hawking, Intel

How to Cite

Wozniak, P., (2019) “Software Emulation of a Hardware Voice Synthesiser”, Fields: journal of Huddersfield student research 5(1). doi:


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Pawel Wozniak (University of Huddersfield)





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