Noise environments in nursing homes : an overview of the literature and a case study in Flanders with quantitative and qualitative methods

As noise is a basic contributor to the evaluation of an environment, the indoor environment of a nursing home (where residents are provided with 24-hour functional support and care) is studied with this focus. General research results, as indicated from a literature review, are limited. Using quantitative and qualitative methods, five nursing homes in Flanders were studied before and after acoustic interventions. Sound levels were measured in individual bedrooms, living rooms and corridors to obtain the typical levels during a day. Acoustic intra-room performance parameters (reverberation time) and inter-room performance parameters (airborne noise insulation level and impact noise insulation level) were measured and compared with Belgian target values. The post operam measurements indicated the potential of the acoustic interventions (use of acoustic curtains, wall and ceiling panels, ventilation grills, floating floors) to improve the building performance and the acoustic climate. From a qualitative viewpoint, the thematic analysis of staff response to the acoustic interventions indicated direct positive outcomes (e.g., more pleasant, quieter indoor soundscapes) with both positive and negative outcomes from perceived indirect effects (i.e., non-acoustic factors)

Wave Based Calculation Methods for Sound-Structure Interaction. Application to Sound Insulation and Sound Radiation of Composite Walls and Floors. (Golfgebaseerde rekenmethoden voor geluid-structuur interactie. Toepassing op geluidisolatie en geluiduitstraling van samengestelde wanden en vloeren.)

In building acoustics, reliable prediction methods for sound transmission and sound radiation are required for parameter studies, material selection and optimization studies. Today there is a lack of calculation techniques which can be used in the entire frequency range of interest. Therefore a numerical prediction tool for building acoustical purposes has been developed in this work. It can be used in a broad frequency range to simulate direct sound transmission through finite-sized, composite walls and floors. The model is based on the wave based method for the acoustic domains and a modal approach to describe the structural response. To model multilayered structures consisting of elastic and poro-elastic layers, the wave based method is combined with the transfer matrix method in a new hybrid model. The full room-structure-room description allows reliable predictions in the low-frequency range. The enhanced computational efficiency of the wave based method compared to finite element models allows calculations at higher frequencies. The model is validated with airborne and structure-borne sound insulation measurements and used to investigate the repeatability and reproducibility of sound insulation measurements in the low- and mid-frequency range. Results focus on the influence of finite dimensions on sound transmission loss of composite structures and the relative importance of source and receiving room. Based on the model, the understanding of sound transmission through lightweight double walls and multilayered structures with air layers is improved. Wave based simulations show the importance of cavity absorption and the vibro-acoustic coupling between plate and cavity modes. Furthermore, experiments and simulations have demonstrated that friction and viscous effects have a very significant influence when thin air layers are involved in sound transmission.status: publishe

Vibration transmission across junctions of double walls using the wave approach and statistical energy analysis

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Development of a hybrid wave based - transfer matrix model for sound transmission analysis

In this paper, a hybrid wave based-transfer matrix model is presented that allows for the investigation of the sound transmission through finite multilayered structures placed between two reverberant rooms. The multilayered structure may consist of an arbitrary configuration of fluid, elastic, or poro-elastic layers. The field variables (structural displacements and sound pressures) are expanded in terms of structural and acoustic wave functions. The boundary and continuity conditions in the rooms determine the participation factors in the pressure expansions. The displacement of the multilayered structure is determined by the mechanical impedance matrix, which gives a relation between the pressures and transverse displacements at both sides of the structure. The elements of this matrix are calculated with the transfer matrix method. First, the hybrid model is numerically validated. Next a comparison is made with sound transmission loss measurements of a hollow brick wall and a sandwich panel. Finally, numerical simulations show the influence of structural damping, room dimensions and plate dimensions on the sound transmission loss of multilayered structures.status: publishe

A Wave Based Model to Predict the Niche Effect on Sound Transmission Loss of Single and Double Walls

In building acoustical laboratories, the sound transmission loss (STL) of building elements is typically measured on the element as mounted in the frame of an aperture. It is known that the specific positioning of the specimen in the frame may affect the results due to the niche effect. In this paper, a wave based model is used to numerically investigate the niche effect on the STL of single and double walls. The field variables (plate displacements and sound pressures) are expanded in terms of structural and acoustic wave functions. The model is validated with experimental results of a lightweight single wall. A parametric study for single and double glazing shows that the position of the wall in the opening and the depth of the niche can significantly influence the STL below coincidence. As for single walls, the STL of double walls is minimal when placed in the center of the niche opening and maximal for the edge positions. The niche effect, however, is larger for double walls in the midfrequency range, where sound transmission is highly dependent on the angle of incidence. Typically, the niche effect leads to a less pronounced, but broader coincidence dip. Furthermore, it is shown that the niche effect can be reduced by the use of a staggered niche. © S. Hirzel Verlag · EAA.status: publishe

Application of the wave based prediction technique to building acoustical problems

The Wave Based Method (WBM) is used to predict the airborne and structure-borne sound insulation of building structures. In building acoustics, the frequency range of interest is 50-5000 Hz. Prediction models in building acoustics often assume infinite structures (like the transfer matrix method) or diffuse sound fields (statistical energy methods). These models cannot explain the inter-laboratory differences typically encountered in the lower frequency range. A wave based prediction model has therefore been developed to describe the direct sound transmission through a structure placed between two reverberant rooms. The rectangular geometry, often encountered in buildings, allows to introduce numerical simplifications which make computations up to 3150 Hz possible on a standard desktop pc. The WBM results are validated with airborne and structure-borne sound insulation measurements of single and double wall structures and a sandwich element.status: publishe

A wave based model to describe the niche effect in sound transmission loss determination of single and double walls

In building acoustical laboratories, the sound transmission loss of structures is typically measured by placing the structure in an aperture between two reverberant rooms. It is known that the location of the specimen in the aperture can affect the results due to the niche - or tunneling - effect. In this paper, a Wave Based Model is used to numerically investigate the tunneling effect in sound transmission loss determination of single and double walls. The field variables (plate displacements and sound pressures) are expanded in terms of structural and acoustic wave functions. The model is validated with experimental results of lightweight single walls. A parametric study for single and double glazing shows that the position of the wall in the opening can significantly influence sound transmission loss below coincidence. As for single walls, the sound transmission loss of double walls is minimal when placed in the center of the niche opening and maximal for the edge positions. The difference, however, is greater for double walls in the mid-frequency range, where sound transmission is highly dependent on the angle of incidence.status: publishe

Numerical Investigation of the Repeatability and Reproducibility of Laboratory Sound Insulation Measurements

An extensive parametric study has been carried out with a wave based model to numerically investigate the fundamental repeatability and reproducibility of laboratory sound insulation measurements in the frequency range 50-200 Hz. Both the pressure method (according to ISO 10140-2) and the intensity method (according to ISO 15186-1 and ISO 15186-3) are investigated. The investigation includes the repeatability of the different measurement procedures, which depends on the influence of the microphone positions and the source position. The reproducibility of the sound insulation measurements in different test facilities is studied by looking at the influence of geometrical parameters like room and plate dimensions, aperture placement and aperture thickness. The results show that for small-sized test elements, the reproducibility of the intensity method is better. For heavy walls and lightweight double constructions, however, the predicted uncertainty is similar for the three measurement methods. The results of the reproducibility study are also used to investigate systematic differences between the pressure method and both intensity methods. © S. Hirzel Verlag.status: publishe

Fast mean and variance computation of the diffuse sound transmission through finite-sized thick and layered wall and floor systems

© 2018 Elsevier Ltd A method is developed for computing the mean and variance of the diffuse field sound transmission loss of finite-sized layered wall and floor systems that consist of solid, fluid and/or poroelastic layers. This is achieved by coupling a transfer matrix model of the wall or floor to statistical energy analysis subsystem models of the adjacent room volumes. The modal behavior of the wall is approximately accounted for by projecting the wall displacement onto a set of sinusoidal lateral basis functions. This hybrid modal transfer matrix-statistical energy analysis method is validated on multiple wall systems: a thin steel plate, a polymethyl methacrylate panel, a thick brick wall, a sandwich panel, a double-leaf wall with poro-elastic material in the cavity, and a double glazing. The predictions are compared with experimental data and with results obtained using alternative prediction methods such as the transfer matrix method with spatial windowing, the hybrid wave based-transfer matrix method, and the hybrid finite element-statistical energy analysis method. These comparisons confirm the prediction accuracy of the proposed method and the computational efficiency against the conventional hybrid finite element-statistical energy analysis method.status: publishe