When the resonator interval is adjusted to 1/4 of the resonance wave lengths, noise reduction in the resonant frequency of double-section resonator becomes the maximum. However, frequency band of noise reduction is limited to one octave which centers on the resonant frequency. In this thesis, four-section resonator and eight-section resonator for 63Hz and 125Hz band were designed by using the design technique by the optimization technique. Furthermore, experimental measurements were done. Noise reduction of 8-10dB was obtained for the design noise reduction 9-10dB. The cause of a fall of the noise reduction in experimental measurements can consider wall vibration and airtightness of resonators.
