The determination of the acoustic properties of sound sources actively controlled in a square duct

This study is to present the determination of the acoustic properties of sound sources actively controlled in a square duct. Therefore, the measurement of sound source reflection coefficient using transfer function technique, the related prediction on sound source impedance and the comparison of the predicted source impedance as described with that of the measurement by using Helmholtz resonator technique are all included in this study. The result of this study, clearly shows that the reflection coefficient of sound source is very dependent on the acoustic frequency involved, and the predicted source impedance by using transfer function method agrees fairly well with that measured by using Helmholtz resonator method.