
Stake attention in this memory
The image shows a classroom setting in Chongqing High-tech Zone, China. In the foreground are several empty white tables with black chairs. A monitor displays a presentation in Chinese about ultrasonic waves, defining them as mechanical waves with frequencies exceeding the upper limit of human hearing (>20,000 Hz). Frequency ranges for infrasonic and sound waves are also listed. A window provides bright, diffuse light.
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