Google’s DeepMind unit, which is working to develop super-intelligent computers, has created a system for machine-generated speech that it says outperforms existing technology by 50 percent.

U.K.-based DeepMind, which Google acquired for about 400 million pounds ($533 million) in 2014, developed an artificial intelligence called WaveNet that can mimic human speech by learning how to form the individual sound waves a human voice creates, it said in a blog post Friday. In blind tests for U.S. English and Mandarin Chinese, human listeners found WaveNet-generated speech sounded more natural than that created with any of Google’s existing text-to-speech programs, which are based on different technologies. WaveNet still underperformed recordings of actual human speech.

Many computer-generated speech programs work by using a large data set of short recordings of a single human speaker and then combining these speech fragments to form new words. The result is intelligible and sounds human, if not completely natural. The drawback is that the sound of the voice cannot be easily modified. Other systems form the voice completely electronically, usually based on rules about how the certain letter-combinations are pronounced. These systems allow the sound of the voice to be manipulated easily, but they have tended to sound less natural than computer-generated speech based on recordings of human speakers, DeepMind said.

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