Have you ever heard of the musical performance of raindrops? In fact, raining is just like a concert, playing the music endlessly and dynamically. Maybe you don't believe that there are different types of rain sounds. Indeed, as the surroundings and weather conditions change, the rain sounds are entirely different.

Generally speaking, there are three sources of raindrop sound:
1. When raindrops are falling through the air, the air flow around the raindrop brings air vibration and results in continuously gentle whispering sound;
2. As raindrops hit the ground or other object surfaces, vibration is triggered with distinctive pattering sound (Sound 1 Top);
3. After raindrops fall and hit a puddle, air bubbles are produced and contract instantaneously. Sound wave is generated at the moment of restoration of water surface (Figure 1), creating the characteristic ‘plink’ sound (Sound 1 Bottom).

The composition of rain music is thus based on these different types of sound.

However, there are far more variations in raindrop sound than we can imagine. Sizes and falling speeds of raindrops, and also different types of the impact surfaces contribute to the diverse range of pitches and dynamics of every note and phrase in the score. For example, vibration frequencies of leaves and stones are not the same, leading to differences in the sounds of raindrops on them. Even though all puddles are accumulation of water, the sound of raindrops on them is still not identical. Since the surface tension of water surface is affected by many factors such as the temperature and impurities, the larger the surface tension, the louder the ‘plink’ sound that it can produce. Moreover, when raindrops of different sizes are impacting the water surface, they generate air bubbles with various diameters. The air bubble produced is like a beaten drum, the larger the raindrop, the lower the pitch is in general. Finally, all these variables, together with the differences in the falling speeds of raindrops, create the melodic rhythms and constitute a piece of rain music.

Although rain music is composed of three types of sound in general, every type is a natural and ever-changing musical instrument. Next time when it is raining, let’s listen to the sound of raindrops and enjoy the unique “rain” symphony performed by the nature.