Atsuo Minemura

Sound radiation from a double-leaf elastic plate with a point force excitation: effect of an interior panel on the structure-borne sound radiation

Abstract The sound radiation from a double-leaf elastic plate subjected to a point force excitation is investigated theoretically, to gain a fundamental insight into the sound radiation from an interior panel of a double-leaf structure in buildings. The effects of the interior panel on the sound radiation, which show a negative effect at low frequencies due to the mass–air–mass resonance, are discussed in detail. The theory is validated experimentally. As a measure of the efficiency of the interior leaf in reducing noise radiation, the radiation reduction is defined in this study, and it is found useful for predicting the sound radiation due to the structure-borne sound in building elements. Parametric studies through theoretical results are made to clarify the effects of the parameters of the sound radiation system, and to gain a fundamental insight into the control of structure-borne noise radiation. It is shown that it is difficult to reduce the radiated sound power by an interior panel alone, even if its mass is increased.

Effect of acoustical damping with a porous absorptive layer in the cavity to reduce the structure-borne sound radiation from a double-leaf structure

Abstract Structure-borne sound radiation from a double-leaf structure with a porous absorptive layer in the cavity is studied theoretically as well as experimentally. The study is for establishing a countermeasure to reduce the structure-borne noise radiated from an interior leaf into rooms and for clarifying its reduction effect. The sound field radiated from a double-leaf elastic plate with layers of arbitrary media in the cavity set into vibration by a point force excitation is theoretically analyzed. The effect of the bulk vibration of an absorptive layer is also considered by a simple model into the present theory. Radiation reduction of an inner-layer derived from the theory is experimentally validated. Parametric studies reveal that increasing the ratio of an absorptive layer thickness to the cavity depth is effective to reduce the structure-borne sound radiation but high flow resistivity of the absorbent material is not necessarily required. A practical equation to predict the mass–air–mass resonance frequency for absorbent cavity case is given in a simple form.

Sound absorption characteristics of a honeycomb‐backed microperforated panel (MPP) absorber

Microperforated panels (MPPs) are typically made of a thin metal or plastic panel and are often unsuitable for an interior finish because thin limp panels do not have enough strength. In particular, an interior finish of room walls requires appropriate strength. In order to solve this problem, a honeycomb structure is attached behind MPPs to stiffen the construction. Thus, it is possible to stiffen an MPP without increasing its thickness, which is important to keep MPPs at their best absorption performance. Furthermore, a honeycomb can increase MPPs’ absorption coefficient in a similar way as a porous layer backed by a honeycomb. In this study, an experiment was performed to gain insight into the acoustical effect of a honeycomb structure behind MPPs and a simple theoretical model to interpret the experimental effects is presented. The experimental results show that the honeycomb affects the absorption characteristics of MPPs: the absorption peak increases and shifts to lower frequencies. This effect beco...

Effect of honeycomb structure in the back cavity on the absorption characteristics of microperforated panel absorbers

Since the principle of microperforated panel absorbers (MPPs) was established, many studies have been made on their practical applications. MPPs are typically made of very thin metal or plastic panels to obtain high absorption. However, such a thin, limp panel is in many cases not suitable for an interior finish of room walls because of its insufficient strength. The authors have proposed to use a honeycomb structure attached behind an MPP to stiffen it without deteriorating its acoustical performance. The honeycomb behind an MPP can also be expected to enhance its absorption performance, considering previous studies on porous sound‐absorbing layers with the back cavity completely partitioned by a honeycomb structure. In this paper, the effect of honeycomb structure in the back cavity on the absorption coefficient of MPP was experimentally studied. The results suggest that the reverberation sound absorption characteristics become close to those of an MPP without a honeycomb structure for normal incidence....

Effect of the mass-spring resonance of a slab covered with carpets on the sound insulation performance

It is well known that the overall sound insulation performance between two adjacent rooms in actual buildings is not so much increased even if a high spec wall is used for the partition because of several flanking sound transmission paths. In recent years, the phenomena that a slab covered with carpets increases the sound transmission through the floor have been found. This is caused by the resonance with the mass of the carpets and the spring of those underlying materials, and consequently the sound insulation performance significantly decreases in the mid-low frequency range. The resonance frequency can be shifted to higher frequencies using formed plastic sheets of higher stiffness for the underlying materials. Although this would usually be one of countermeasures to increase the overall sound insulation performance, it is not a fundamental solution for noise control engineering. In the present work, in order to control the mass-spring resonance itself, a method of focusing on permeability of the carpe...

Effect of vibration of porous absorbent layers in the cavity of a multiple‐leaf structure on its acoustic properties

Porous absorbent layers are often used in the cavity of multiple‐leaf acoustic panels in buildings to reduce the sound power radiated by the panels or to enhance the panel absorption. It is known that bulk vibration of the porous layer can result in the reduced transmission loss of the multiple‐leaf acoustic panel. This work presents a simple method to account for the effect of the bulk vibration of the layer on its acoustic resistance. In this method the ‘‘modified’’ flow resistance of the layer is defined as the real part of the parallel impedance in the electro‐acoustical equivalent model. The model relates the impedance to the flow resistivity and the density of the porous layer. The ‘‘modified’’ flow resistance is then used to predict the propagation constant and the characteristic impedance of the material using the appropriate model for sound propagation in rigid‐frame porous materials. As an application, the effect of a porous layer in the cavity of double‐leaf panels on the radiated sound power i...