Suppression of low frequency sound transmission in fluid-filled pipe systems through installation of an anechoic node array

Abstract

To provide low frequency noise control in the fluid-filled pipe systems of ships, a periodic waveguide made of an array of expansionary mufflers (referred to as anechoic nodes) installed axially on a pipe is proposed. Broad and low frequency acoustic band gaps can be generated with this periodic pipe system from the destructive interference of reflected, transmitted, and incident waves at the muffler installation nodes, and will be reinforced over some desired low frequency ranges. Within the band gaps, the transmission of acoustic noise inside the internal media of the periodic pipe system will be effectively attenuated. Key parameters for modulating the central frequency, bandwidth, and attenuation coefficient of the band gaps include the lattice constant, expansion ratio, and muffler length, and these factors are investigated following analysis of the formation mechanism of the band gaps. The results obtained in this study suggest that the introduction of a muffler array to form a periodic structure in the piping system can suppress the propagation of acoustic waves with longer wavelengths, thus achieving control of lower frequency pipe noises.

Defect mode properties of an acoustic structure made up of periodic expansion chambers containing defects

“…These two bands are surround a central band gap of 60Hz in its width. The control of acoustic wave propagation mainly depends on the resonance of the expansion muffler and the periodicity given by all the regularly spaced mufflers [10,16].…”

“…The effects of noise elimination by unit cell of an expansion muffler and the periodicity along the main waveguide has it influence on band gap widths and muffling effects at lower frequencies [16]. In this case, many parameters are investigated to control bandwidth, such as the resonance frequency, the period including dimensional parameters of the expansion chamber are investigated.…”

Pengaruh Konfigurasi Geometri Buffer Resonator Tipe-H terhadap Intensitas Bunyi

“…dengan 𝐽 𝑚 adalah fungsi Bessel bentuk pertama, dan 𝛼 𝑚𝑛 adalah akar ke-𝑛 dari persamaan yang mengandung fungsi Bessel orde ke-𝑚 Saluran buffer dan resonator tergandeng satu dengan lainnya sehingga bentuk ragam normal azimuth haruslah ortogonal dan sesumbu serta membentuk sistem resonator tipe-H, 𝑚 = 0. Dengan demikian tekanan dan kecepatan akustik dapat ditulis sebagai berikut [13]…”

Investigation on low-frequency sound propagation characteristics of fluid-filled steel pipeline

“…In the low frequency band, the noise of sea pipeline system is dominated by the line spectrum in the low frequency band [1], these low frequency noise will propagate along the wall in the form of vibration [2], which is difficult to be eliminated by the traditional muffler. At present, there are few studies on the sound propagation of elastic fluid-filled pipeline, and most of the understanding of pipeline acoustics stays at the stage of gasfilled pipelines [3][4][5][6], due to the lack of accurate understanding of the sound propagation characteristics of fluid-filled pipelines, many researchers use plane wave assumption to simplify the calculations, and have designed many pipeline mufflers for liquids in pipelines [7][8]. However, the difference between the characteristic impedance of the liquid and the steel is not very obvious.…”