Strike the bigger gong with the mallet. Listen to the sound it makes. Place your hand near the gong’s surface, not touching it. You will feel vibrations of the air surrounding the gong. Move your hand around and explore how the intensity of vibrations changes in different places. Repeat, striking the gong in a slightly different place. Then repeat the same also with the smaller gong. Remember: never strike the very center of the gong. It could damage the instrument.