The most common noise control systems are already based on passive and active techniques. Passive noise control is a typical technique for high frequency noise and active noise control also for low frequency noise. In this paper, a simple and cheap method is proposed to determine the difference between sound waves of two centrifugal fans based on time delay in power starting to control low frequency noise.The highest level in the noise level analysis shown in study fans is at 250 Hz. In the interference stage of study, noise measurements were recorded in the time delay of 3, 6 and 8 ms for power start for one of the fans. Results showed that an 8 ms time delay resulted in 1.3 - 2.3 dB(L) reduction in total sound pressure level of fans. This method is suggested for noise control of low frequency in the same sources.
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