Jaime Llinares

Effect of the rockwool bulk density on the airborne sound insulation of lightweight double walls

Abstract In this paper, results from measurements of the sound reduction index of some double walls are presented. The walls are made from gypsum boards and filled with sound-absorbing material (rockwool) in the gap. The results from the measurements show the influence of rockwool bulk density on the sound reduction index.

Two-dimensional elastic bandgap crystal to attenuate surface waves

Experiments on the attenuation of Rayleigh waves in a marble quarry by a periodic array of cylindrical holes, in a honeycomb and in a triangular distribution, are reported. The results are explained in terms of elastic wave crystals (EWCs), and compared to theoretical calculations performed with scalar waves. The scaling property of the underlying theory has led us to explore the possible application of the results obtained to the attenuation of surface waves in seismic movements.

Design of lightweight multilayer partitions based on sonic crystals

The sound transmission coefficient of different multilayer partitions commonly encountered in buildings has been measured as a function of frequency. Most of the samples studied showed an increase in the sound transmission coefficient over a specific frequency, called the critical frequency, depending on the layer material. However, for partitions built with the same materials, but built with a periodic arrangement of layers, this behavior has not been observed. This kind of periodic multilayer partition can be considered as a sonic crystal, because the stopband corresponding to a one-dimensional sonic crystal with a constant lattice equal to the modulation of the partition is in the same range as the critical frequency of the panel.

Sound attenuation by a two dimensional array of cylinders

Here, it is shown, for the first time, a systematic analysis (experiment and theory) of the acoustic transmission of a two‐dimensional periodic array of rigid cylinders with two different configurations: square and triangular. The influence of the filling fractions, ranging from 0.06 up to 0.41, on the appearance of the pseudogaps and full band gaps is studied. Above a certain filling fraction, an overlap is observed between the attenuation peaks measured along the two high symmetry directions of the Brillouin zone. This effect is considered as the fingerprint of the existence of a full acoustic gap. Nevertheless, the comparison with our calculation of band structures shows that the lattice has band states in that frequency range. These bands are called deaf bands (i.e., they cannot be excited by experiments of sound transmission) [Sanchez‐Perez et al., Phys. Rev. Lett. (to be published)].

Influence of screw spacings on sound reduction index in lightweight partitions

Abstract In this paper measured sound reduction index data for lightweight partitions with gypsum board layers attached to the frame with two different screw spacings are presented. Data are used to show the effect of screw spacings and to quantify the effect on sound reduction index. The results show that screw spacing had a great effect in double walls where each gypsum board layer was attached to each side of a timber frame.

Influence of air layers and damping layers between gypsum boards on sound transmission

Abstract In this paper the influence on sound reduction index of a thin air layer between gypsum board layers of lightweight partitions has been examined. It has been shown that the air layer between gypsum boards causes a decrease in sound reduction index due to mass-air-mass resonance. When the thin air layer is filled with a damping layer, the sound reduction index is increased for frequencies around the critical frequencies. Predictions show similar effects to those measured.

Comment on : Theory of tailoring sonic devices : Diffraction dominates over refraction

Recently, Garcia et al. [Phys. Rev. E 67, 046606 (2003)] studied theoretically several acoustic devices with dimensions on the order of several wavelengths. Those authors also discussed experimental results previously reported by several of us [Phys. Rev. Lett. 88, 023902 (2002)]] and concluded that it is diffraction rather than refraction that is the dominating mechanism explaining the focusing effects observed in those experiments. In this Comment we reexamined their calculations and discussed why some of their interpretations of our results are misleading.

Technical Note: Comparison of the Sound Insulation of Lightweight Partitions with Different Sound Absorbing Infills

Measurements of sound reduction indices for lightweight gypsum board partitions filled with three different sound absorbing materials (rockwool, glasswool and polyurethane foam) are reported. For partitions where the gypsum panels are mounted on a common stud, with the sound absorbing infill in direct contact with both panels and for uncoupled double partitions, measurement results show that polyurethane foam, of high flow resistivity and stiffness, is less effective as an infill than either rockwool or glasswool.

Sound transmission loss of tiled brick walls

Walls made from hollow bricks joined with mortared joints are often found in the construction of buildings. Brick walls are also used as noise barriers. Over time, mortared joints develop gaps and cracks that reduce the noise-reduction capability of a brick wall. Ceramic tiles or a combination of plaster and ceramic tiles can be applied to the surface of a brick wall to improve the noise reduction as well as the visual appearance of the wall. This paper reports the results of measurements of the sound transmission loss of test specimens of brick walls faced with ceramic tiles. Tiles were applied to the surface of the bricks by two methods: (1) with dabs of a sand-cement mixture and (2) by means of a commercial tile adhesive. For some test configurations, a coating of plaster was first applied to the surface of the brick wall. Wall test specimens were constructed using 70-mm-thick or 110-mm-thick hollow bricks. The greatest improvement in sound transmission loss (and in the corresponding sound transmission class [STC] rating) was provided by wall test specimens where both sides were coated with plaster and with tiles applied to one side by dabs of the sand-cement mixture.

The Characterisation of Fibrous Materials from Measurements of Absorption Using Techniques Based on Miki's Model

At present theoretical and experimental models exist from which the complex propagation constant and the complex impedance characteristic of a fibrous material can obtain [1-4]. Voronina’s Model does not require experimental results. Using this model (method), one can obtain the specific impedance and the propagation constant from the structural characteristic, Q, which in turn depends on the density and diameter of the fibre, density of material, etc. From the impedance characteristic, one can calculate the reflection coefficient for normal incidence, which is related to the absorption coefficient [5-6]. In this work we present a method which, taking measurements of absorption as its starting point and using Voronina’s Model, allows us to arrive at a complete characterisation of a fibrous material, and even to obtain the average diameter of the fibres [7] of which the material is formed.