TUNING FORK This instrument is provided for middle schools to make experiments on sound resonance. It can be used to test sound occurrence and the relation between sound tuning and frequency, and it also can be used as sound-setting standards for other musical instruments. The frequencies of the four-tuning-fork instrument are as follows: 128HZ, 256HZ, 512HZ, 1024HZ The frequencies of the eight-tuning-fork instrument are as follows: 256HZ, 288HZ, 320HZ, 341.3HZ,384HZ, 426.6HZ, 480HZ, 512HZ The frequencies of the thirteen-tuning-fork instrument are as follows: 256HZ, 266.6HZ, 288HZ, 300HZ, 320HZ, 341.3HZ, 355.5HZ, 384HZ, 400HZ, 426.6HZ, 444.4HZ, 480HZ, 512HZ