I cannot provide specific information on the number of people who may have started hearing voices since that time or beyond.
If you or someone you know is experiencing distressing auditory hallucinations (hearing voices), it is essential to seek professional help from a mental health specialist. A mental health professional, such as a psychiatrist or psychologist, can conduct a thorough assessment, provide a proper diagnosis, and recommend appropriate treatment options tailored to the individual's needs.
Regarding your comment about recording running water and using a vocoder, I'm not entirely sure what you are referring to in this context. A vocoder is an electronic device or software effect that manipulates the sound of a human voice or an instrument by combining it with the signal from a synthesizer. However, I'm unsure how this would be related to stopping the experience of hearing voices.
Again, if you or someone you know is experiencing auditory hallucinations or any other mental health concern, it's essential to reach out to a healthcare professional for support and guidance. Mental health conditions are treatable, and seeking help is a positive step towards improving one's well-being.