To design an experiment to test the speed of sound in different materials, you could use a speaker and a microphone to measure the time it takes for sound to travel through each material. First, you would need to set up the speaker and microphone on opposite sides of each material and measure the distance between them. Then, you would play a sound from the speaker and measure the time it takes for the sound to reach the microphone. You could repeat this process for each material and use the data to calculate the speed of sound in each material. Additionally, you could compare your results to the known speed of sound in air (343 m/s) to see how the materials affect the speed of sound.