Acoustic noise synthesis for duct systems

Studies on acoustical noise from duct systems are important in their design and performance. A methodology is presented for simulation of acoustical noise from a duct system which can be modeled in terms of source, duct element and termination. In this methodology first the transfer function of the given duct system is evaluated using the four pole parameters of the duct system, source strength, source acoustic and termination acoustic impedances. Then the impulse response of the predicted transfer function is convolved with source signal to obtain the acoustic noise output of the duct system in frequency domain. In order to verify this methodology, the simulated noise is compared with experimentally measured noise for two types of duct systems namely a straight pipe and a simple expansion chamber. The results show good agreement between the simulated and measured noise spectra. The methodology presented in this work provides the capability of simulating the noise of a duct system from its design before it is actually built. Also sound quality studies can be based on design that would assist in reaching the final design to be fabricated.