Abstract
Helmholtz resonators are commonly used for tuning of acoustic systems such as industrial processes, ICE exhaust, engine manifold systems, and also used as devices to control the intense sound fields generated within jet engines The work presented here considers a system that modifies the acoustic response of acoustic dynamics in the audio duct with Helmholtz resonator, The system consists of a static Helmholtz resonator and an active control of an audio speaker that provides a variable acoustic frequency. In this paper; an extensive experimental measurements of the acoustic pressure by using two microphones system techniques have been used to measure the net acoustic power transmission in the duct downstream of Helmholtz resonator, to get an optimum performance over a range of excited frequencies. The acoustic wave signals are traveling in the duct as a plane wave, these waves are generated by a signal generator system with a know wave (sine wave). The acoustic pressure fluctuation is measured by two microphones system, the first microphone is located closed to the speaker, and the other is located at the end of duct, and the Helmholtz resonator is positioned near the loudspeaker. Four types of necks (cylindrical perforated and non perforated neck with different length) have been studied in this paper. The results show that, longer perforated neck achieves the strongest reduction of noise. This study makes available very detailed power spectra of two simultaneously measured acoustic pressure signals in the acoustical duct with and without Helmholtz resonator of the different types of necks. Keywords (Helmholtz resonator, acoustic pressure, power spectrum, and noise reduction)