Please note that the effect you are seeing in the video cannot be seen with the naked eye. The reason why you see the water remain motionless is because the footage is filmed at 24 frames per second, just like the sine wave that comes out of the speaker.
Run the rubber hose down past the speaker so that the hose touches the speaker. Leave about 1 or 2 inches of the hose hanging past the bottom of the speaker. Secure the hose to the speaker with tape or whatever works best for you. The goal is to make sure the hose is touching the actual speaker so that when the speaker produces sound (vibrates) it will vibrate the hose.
Set up your camera and switch it to 24 fps. The higher the shutter speed the better the results. But also keep in the mind that the higher your shutter speed, the more light you need. Run an audio cable from your computer to the speaker. Set your tone generating software to 24hz and hit play.Turn on the water. Now look through the camera and watch the magic begin. If you want the water to look like it’s moving backward set the
frequency to 23hz. If you want to look like it’s moving forward in slow motion set it to 25hz.