NOISE-ABSORBING ACOUSTIC SCREEN BASED ON A HELMHOLTZ RESONATOR

The paper aims at studying the noise protection potential of an acoustic screen based on a Helmholtz resonator to solve the problem of noise reduction level in the area in front of the screen. For experimental analysis, a modular acoustic screen has been made. Replaceable modules are made on the basis of a wooden frame with stiffening ribs, one side of the module is blind, another has slotted holes, which ensures the formation of noise absorbers on a Helmholtz resonator principle. Changing the position of the modules in the support racks provides the ability to change the screen reflexive surface nature. The main problem solved in this work is to experimentally determine the decrease magnitude in the sound pressure level in the area in front of the screen. The results of sound pressure level measurements at various frequencies are provided, the comparison of the reflected noise obtained values with the results obtained in the sound pressure level analysis in the case of a solid screen is given. The coincidence of the calculated values of the active sound absorption frequencies with the measured values is shown. It is concluded that there is a possibility to solve the nose reduction level problem when using such screens in areas where people can be.

Study of the Active Acoustic Absorber Based on a Shunted Loudspeaker

The study looks at the active sound absorption system in which a loudspeaker with a shunting resistor is used as an absorber. A theoretical study of shunting element influence on the reviewed system absorption characteristics was performed. Results of experimental re-search of active acoustic absorbers are given.

From Local Structure to Overall Performance: An Overview on the Design of an Acoustic Coating

Based on the requirements of underwater acoustic stealth, the classification and research background of acoustic coatings are introduced herein. The research significance of acoustic coatings is expounded from the perspective of both the military and civilian use. A brief overview of the conventional design process of acoustic coatings is presented, which describes the substrates used in different countries. Aimed at the local design of acoustic coatings, research progress on passive and semi-active/active sound absorption structure is summarized. Focused on the passive acoustic coatings; acoustic cavity design and optimization, acoustic performance of acoustic coatings with rigid inclusions or scatterers, and acoustic coatings with a hybrid structure are discussed. Moreover, an overview of the overall design of acoustic coatings based on the sound field characteristics of the submarine is also presented. Finally, the shortcomings of the research are discussed, breakthroughs in acoustic coating design research are forecast, and the key technical issues to be solved are highlighted.