A few days ago, Xv Fang and Feng Jian found a total of five volunteers from Binhai University who felt a hypnotic effect from the rustling sound of rain.
Over the weekend, Dr. Qiu Ge used the hospital laboratory's precision instruments and equipment to conduct more precise tests and examinations on the five student volunteers.
The test results were somewhat surprising to Yan Feifan.
Dr. Qiu told Yan Feifan over the phone that while all five volunteers had a drowsy reaction to the 20,260-hertz audio stimulus, this high frequency didn't produce the strongest stimulative effect.
Further testing revealed that the optimal audio frequency for inducing sleepiness was different for each of the five individuals. The maximum was 20,310 hertz, and the minimum was 20,240 hertz.
Dr. Qiu suggested that Yan Feifan and Wang Chuan also get tested to determine their own optimal high-frequency range.
