Abstract: The principles of measuring sound velocity using standing wave method and phase difference method are presented through numerical calculation combined with traveling wave method. The differences between standing wave method and phase difference method in measuring sound velocity are compared, and the influence of air absorption coefficient, reflection coefficient, and measurement distance on the accuracy of sound velocity measurement is discussed. Theoretical analysis and experiments show that standing wave method behaves accurately at a slightly smaller distance from the sound source, while phase method behaves accurately at a slightly larger distance. Whether it is standing wave method or phase difference method, experimental measurement results always deviate positively from the true value. Overall, the accuracy of phase method is better than that of standing wave method. The sound field distribution between transducers is a mixed wave between standing wave and traveling wave. When the reflection coefficient is larger, the standing wave effect is obvious. When the absorption coefficient is large, the traveling wave effect is obvious. When the measurement distance is small, the standing wave effect is obvious and when measuring distance is larger, the traveling wave effect is significant

Key words: sound speed, standing wave, traveling wave, sound pressure