Rain drop sound / Rain drop sound

Water and oil are sensitive liquid. It gives rise to a wavelength from subtle vibrations. When the water and oil close to Loud speaker with severe vibration, It cause a wave and draw a smooth curve. The wavelength looks like Raindrops falling on the floor. It makes us to feel sentimental. Then, in Loud speaker cases, We create a wide and thin gap in the form of cable, and hear the sound from the gap.