The design of low-frequency sound absorbers with broadband absorption characteristics and optimized dimensions is a pressing research problem in engineering acoustics. In this work, a deep neural network based inverse prediction mechanism is proposed to geometrically design a Helmholtz resonator (HR) based acoustic absorber for low-frequency absorption. Analytically obtained frequency response from electro-acoustic theory is deployed to create the large dataset required for training and testing the deep neural network. The trained convolutional neural network inversely speculates optimum design parameters corresponding to the desired absorption characteristics with high fidelity. To validate, the inverse design procedure is initially implemented on a standard HR based sound absorber model with high accuracy. Thereafter, the inverse design strategy is extended to forecast the optimum geometric parameters of an absorber with complex features, which is realized using HRs and a micro-perforated panel. Subsequently, a quasi-perfect low-frequency acoustic absorber having minimum thickness and broadband characteristics is deduced. Importantly, it is demonstrated that the proposed absorber, comprising four parallel HRs and a microperforated panel, absorbed more than 90% sound in the frequency band of 347–630 Hz. The introduced design process reveals a wide variety of applications in engineering acoustics as it is suitable for tailoring any sound absorber model with desirable features.

Recently, increased attention has been given to minimize the effects of noise pollution on living beings. The attenuation and manipulation of sound waves with low-frequency components are quite difficult with traditional absorbers due to inherent properties induced by large wavelengths and yet are particularly critical to modern designs. In this study, a parallel arrangement of a coiled-up space cavity and micro-perforated panel (MPP) is considered as the absorber configuration. The coiled-up space consists of a front panel with an orifice and a rigid backing panel enclosing an arch-shaped concentric channel. The entire coiled-up space length is provided with two varying cross-sections. By this arrangement, the sound path is squeezed into a reasonably small volume enabling sound absorption at low frequencies. A thin panel with numerous perforations is the main constituent of MPP. It is backed by an air cavity and terminated by a rigid backing. Here in this configuration, micro perforations are provided on the front panel of the coiled-up space, which ensures simultaneous entry of acoustic waves into the micro-perforations and coiled-up space structure. The absorption characteristics of the present configuration are studied numerically and analytically. The combined structure with parallel combination of coiled-up space and MPP resulted in the abatement of more than 70% of sound in the frequency range of 321 Hz to 853 Hz. The present absorber has only a 5.5 cm thickness, which is subwavelength$\left(\frac{\lambda }{19}\right)$ also.

Low-frequency broadband sound absorption with minimal dimensions and material cost is an ongoing research challenge in engineering acoustics. Common acoustic structures, such as microperforated panels (MPPs) and porous structures, are ineffective in alleviating low-frequency noise. In this context, a sound-absorbing panel consisting of two axially coiled-up tubes and MPP is proposed for effective low-frequency noise abatement. Initially, an electro-acoustic analogy-based analytical approach is developed to predict the acoustic absorption performance of series and parallel configurations of MPP and coiled-up tubes, and the findings are corroborated by full-field finite element simulations. The parametric analyses revealed that by carefully choosing the geometric features of the coiled-up tubes, the absorption spectra of each tube can be coupled with that of MPP. Thus the bandwidth of absorption can be broadened. Furthermore, it is observed that the parallel configuration of MPP and coiled-up tubes significantly lowered the thickness of the absorber without affecting the absorption bandwidth. Importantly, the parallel configuration of MPP and coiled-up space demonstrated more than 80% absorption in the frequency range of 250–350 Hz.