The Man Who Gave Steven Hawking His Voice

Stephen Hawking’s voice was very popular it rivalled his revolutionary theories on quantum physics, black holes, and theoretical cosmology. Hawking, who is regarded as the most well-known theoretical physicist of his time, significantly improved our comprehension of black holes by foreseeing their capacity to generate heat radiation (now known as Hawking radiation).

Hawking’s voice and appearance, however, captured the public’s attention as a genuine representation of the victory of the mind over matter. It is commonly known that in his twenties, Hawking received a diagnosis of Motor Neuron disease, also known as amyotrophic lateral sclerosis, a condition affecting the brain and spinal cord nerve cells responsible for voluntary movement. Hawking fully lost his capacity to talk after undergoing an emergency tracheotomy in 1985, as he detailed in his autobiography:

For a time, [after the tracheotomy] the only way I could communicate was to spell out words letter by letter, by raising my eyebrows when someone pointed to the right letter on a spelling card. It is pretty difficult to carry on a conversation like that, let alone write a scientific paper.

Hawking received a diagnosis of Motor Neuron disease, a condition affecting the brain and spinal cord nerve cells responsible for voluntary movement

This is where American scientist Dennis Klatt’s work entered the picture. Klatt, a pioneer in voice synthesis, contributed to numerous developments in the automated production of high-quality human speech. For instance, researchers working to synthesize speech sounds still utilize his formant synthesis software, which was published in the Journal of the Acoustical Society of America in 1980.

The “KlattTalk” TTS (text-to-speech) system, which is a text-to-text speech system, was also developed with help from Klatt. People with disabilities used this frequently, especially those with impaired vision who utilized it to read computer text aloud. Klatt, sometimes known as “Perfect Paul,” who rose to fame as Professor Stephen Hawking’s voice, was one of these voices.

Klatt, sometimes known as “Perfect Paul,” who rose to fame as Professor Stephen Hawking’s voice

When offered newer models, like the Speech Plus synthesizer in 1988, Hawking decided to stick with Klatt’s because he grew so attached to it and thought of it as a part of his identity. As a result, technology allowed Hawking to speak, as opposed to suffering from locked-in syndrome, a condition that causes a person to be confined to their body and unable to express themselves. Hawking gave the device high ratings in his autobiography:

This system allowed me to communicate much better than I could before …Using this system, I have written a book, and dozens of scientific papers. I have also given many scientific and popular talks …I think that this is in a large part due to the quality of the speech synthesizer.

The Creation Of Klatt’s Creation

KlattTalk was used by additional technicians and researchers to build a portable computer for Professor Hawking’s wheelchair. Notably, Digital Equipment Corporation created KlattTalk for commercial use in 1983; it later adopted the name DECtalk. Initially, Hawking’s speech was managed by a hand switch that let him choose words by navigating menu selections on his computer screen.

Later improvements solely responded to his head and eye movements and used infrared beam switching. Before switching to a newer system that produced a more realistic-sounding voice, the Speech Plus Call Text 5010 synthesizer, in 2014, Hawking used the DECtalk speech synthesizer.

the Speech Plus Call Text 5010 synthesizer, in 2014, Hawking used the DECtalk speech synthesize

He continued to use Perfect Paul’s voice despite the system change: “I keep it because I have not heard a voice I like better and because I have identified with it.” Hawking even granted permission for Perfect Paul to be used in his 2014 biography, The Theory of Everything, because his voice had grown so recognizable. Numerous tracks, including “Keep Talking” by Pink Floyd and “Fitter Happier” by Radiohead, feature recordings of his voice.

Klatt’s Legacy Lived On

Hawking’s voice came to be recognized as his own, although Perkell always equated it with Klatt. He said, “Wow, I’m watching Stephen Hawking and out comes Dennis’ voice,” according to Witness History. Unfortunately, Klatt was given a thyroid cancer diagnosis in the early 1980s, and his laryngeal tissues eventually stopped working as a result of the treatment.

Ironic, I say. He lost himself in his attempt to mimic his natural voice, according to Perkell. Despite his illness, Dr. Klatt kept working and persevered with optimism until his death in 1988 at the age of 50. But his voice continued. It was never the case, according to Perkell, that I didn’t think of Dennis when I heard Hawking talk. Thus, Hawking carried on Klatt’s legacy in a way that undoubtedly reflected Klatt’s most notable success with voice synthesis.


  • Carr, Bernard J, et al. “Stephen William Hawking CH CBE. 8 January 1942-14 March 2018.” The Royal Society Publishing. [Accessed on 23 February 2022].
  • Kewley-Port, Diane, and Terrance M. Nearey. “Speech Synthesizer Produced Voices for Disabled, Including Stephen Hawking.” The Journal of the Acoustical Society of America 148, no. 1 (2020): R1–R2.

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