You can use a strobe light combined with sound to cause water to flow back.
The main reasons why water backflow occurs when speakers and strobe lights work together are:
1. The bass frequency of the speaker is very low, only about 24 Hz.
2. Such a low frequency can impact water flow in the form of water droplets. If you use a camera to record it, you will see from the video that the water droplets are basically still, as if. they still are.
3. If the bass frequency increases at this time, people will have the feeling of reflux with the naked eye.