The system, known as WaveNet, is able to generate human speech by forming individual sound waves that are used in a human voice. Additionally, because it is designed to mimic human brain function, WaveNet is capable of learning from extremely detailed -- at least 16,000 samples per second -- audio samples. The program statistically chooses which samples to use and pieces them together, producing raw audio. While most of the existing TTS systems also use the same "piece by piece" idea, they largely utilize concatenative TTS. Despite drawing from a large database, these systems are restricted to combinations of short recorded speech fragments from a single speaker, which makes modifying the voice or its inflection difficult.