Abstract
Sound absorbing characteristics for perforated panel at ultra low frequency were studied. Principle of sound absorption of perforated panel has two mechanisms. One is friction loss in a flow of cylindrical tube, which is proportional to particle velocity in a hole. The other is pressure loss as orifice, which is proportional to square of particle velocity in a hole. Therefore sound absorbing characteristics are depend on sound particle velocity and sound pressure level. We applied calculation method to predict the sound absorbing characteristics of perforated panel in ultra low frequency region by using transfer matrix method and measured those at ultra low frequency using two-microphone method. Calculated values are in good agreement with measured values.
