No abstract

Hollow bricks and blocks are one of the most common forms of material used for wall construction found in Central and Southern Europe. The principle purpose of the perforations (holes) is to increase the thermal insulation properties. As a result of these perforations the block gross density is reduced significantly and these block walls have high anisotropy. Consequently, the acoustical insulation properties are influenced detrimentally in comparison to solid blocks. Due to the large thickness of some of these types of hollow block thick wall effects can occur such as bending shear waves and thickness resonances. These further reduce the sound insulation at high frequencies. This paper describes the characteristic features of sound transmission through hollow walls. For this study several different types of wall were built of varying thickness and materials and the sound reduction index was recorded. The effects of additional plaster layers is also discussed. It is suggested that the material properties of the block's complex web structure may strongly influence the sound reduction index at the low and high frequencies.

This paper describes the results of the European Inter-Laboratory Test (ILT) program, conducted for the determination of repeatability and reproducibility values for the laboratory measurements of airborne sound insulation of walls. A total of 24 laboratories took part in this ILT, 21 belonging to the European Community. Two test structures were constructed; a double lightweight wall and a single lightweight wall, both built of plasterboard. The sound reduction index values were measured. The main result of the ILT was the significant difference obtained for the reproducibility value, R, for the double lightweight wall with values up to 12 dB at middle-highfrequencies. On the contrary, the reproducibility value for the single wall was very similar to the tentative values indicated in Annex A of ISO 140-2. Good agreement between laboratories was found for both structures in the computed repeatability values, r.

In order to improve the reliability of down-hole electronics Quartzdyne Electronics has invested over 10 million device test hours in life testing of our circuits in both powered and un-powered modes. In addition to time at temperature, these tests include thermal cycling and high impact drop testing. While resistors tend to be generally reliable, we have observed resistance drift in some units that has pushed circuit performance outside of accepted electrical specifications. In an attempt to comprehend the root cause(s) of resistance drift, failed samples have been studied in a scanning electron microscope. The resulting observations have led to structured designs of experiment to isolate the many possible root causes. This paper will present these observations, experimental outcomes and draw conclusions surrounding thick film vs. thin film performance, variations between value ranges, differences between vendors, and a possible link relating the drift mechanism to the method and extent of value trimming. This information should be useful to resistor vendors interested in improving the quality and performance of their products.

In an inter-laboratory test programme (ILT) for the measurement of airborne sound insulation of lightweight walls, reproducibility values of up to 12dB were obtained from the sound reduction index measured in 21 participating laboratories. These high reproducibility values were for a test structure composed of lightweight plasterboard panels, forming a double wall, mounted on separate metal ´C´ channels. This paper presents possible reasons for the large reproducibility values for the double wall using experimental investigations and theoretical models using Statistical Energy Analysis (SEA). Whilst the sound reduction index(SRI) does take into account the different test wall areas and reverberation times of the respective laboratories involved, some factors which may influence the measured SRI values are not. It is suggested that the principle factor which may have effected the SRI values of this test programme for the double wall was the lining material of the test aperture in the various laboratories which can provide a flanking transmission path between both sides of the double wall. Other factors are discussed which may also play a contributory role in causing differences in the measured SRI values such as sill/reveal size, aspect ratio, panel-channel connections and workmanship.