Perforated elements are extensively used in silencers or mufflers for intake and exhaust systems of various fluid machines. The perforates are usually exposed to the gas flow and it is known that the flow is greatly influential to the acoustic characteristics of the perforated silencer. This study is concerned with the measurement and empirical modeling of the acoustic impedance of circular perforate holes with grazing flow. Impedance measurements by coupled the two microphones at the same transverse position have been carried out with the variation of involved flow, geometric, and dynamic parameters: grazing mean-flow velocity, diameter and thickness of perforates, porosity, frequency. From the various kinds of measured data under the parametric variation, an empirical impedance model for circular perforates is proposed by nonlinear regression in the statistical manner. The sensitivity of proposed empirical model is investigated through the example calculations of the transmission loss for acoustically long and short concentric tube resonators. Theoretically predicted transmission losses, which employ the present acoustic impedance model for the perforated hole, and measured ones for nine concentric tube resonators in the presence of low Mach number, grazing flow are compared and they show good agreements, thus providing the validation for the present empirical impedance model.