Laboratory Mock-up Research Articles

Side-branch resonators for controlling industrial pressure blower noise.

Process industries commonly use fans and pressure blowers that operate at pressures of 5 psig and flow rates around 5000 cfm. These fans and blowers often create some of the highest localized sound levels in an industrial environment. Centrifugal blowers create blade passage tones that produce intense sound levels in the range of 150–160 dB(A) at the outlets, due to high-pressure volume flow and blade passage rate. A case study is presented to show the effectiveness of the old idea of the side-branch resonator in dramatically reducing the fundamental frequency of the blade passage tone [W. H. Ihde, Noise Control Eng. 5(3), 131–135 (1975)]. Fundamental tone reductions of 25–30 dB have been observed in laboratory mock-ups for a single side branch, and a reduction of 36 dB has been observed in a practical industrial application using two side branches. For constant-frequency tones, the side-branch resonator offers an inexpensive alternative to active noise control, and is effective at very intense sound levels and extreme temperatures.

Sensitivity of a Cigarette Ignitability Index to Hypothetical Shifts in the Distribution of Upholstery Furniture Fabrics

The laboratory mock-up model is the procedure employed to esti mate the likelihood of an upholstered furniture product to ignite when in sus tained contact with a burning cigarette. To draw inference from these mock-up laboratory tests an ignitability index, reflecting the expected probability of an ignition, is developed. This index is dependent upon the distributions of the fabrics and battings which are at risk. This study examines the sensitivity of the index to shifts in the fabric and batting distributions. Under these simulated fabric and battings shifts the ignitability indexes for several ciga rettes of differing properties are compared.

Alterability of the French LWR Solution Reference Glass in Repository Conditions

AbstractThe disposal of glass blocks containing fission products in granitic geological formations is one of the options currently investigated in France. This paper discusses the major criteria selected to develop models of such repositories and gives the first results obtained with the corresponding experimental test. Five laboratory mockups corresponding to different alternatives regarding the fill materials were prepared. The following materials were used to encase the French LWR reference glass:- Test I : Granite, sand, stainless steel;- Test 2 : Granite, sand, illite, stainless steel;- Test 3 : Granite, sand, bentonite, stainless steel;- Test 4 : Granite, sand, Al2O3, ceramic, stainless steel;- Test 5 : Granite, sand, haitalloy C4.Samples were taken of the solutions obtained in the preconditioning cell and in contact with the glass to assess the glass corrosion behavior in each of these media. The experiments were completed by surface analyses designed to compare the morphology of the surface layers that develop with and without the environmental materials.

Microwave diffraction for steel strip detection

A system has been devised and tested successfully in a laboratory mock-up to tackle the problem of detecting the presence of a metal strip in the particularly hazardous environment of a steel works. This paper briefly outlines the environmental problems, and how they defeated more conventional techniques, before moving on to the basic principles involved with using microwave diffraction for detecting the strip. Modifications are then described to the fundamental concept which are needed to overcome practical problems. The paper finally outlines how the technique can be installed into the existing bed with very little disruption to the practical set-up and also gives a rough idea of costs involved.

The Problem of Acoustical Specifications for Office Landscape Ceilings

Laboratory mockup measurements of interzone attenuation and subjective judgments of speech privacy can be coordinated through the structure of speech-intelligibility theory to evolve a method of ceiling characterization that offers a sensitive scale for performance evaluation with respect to office landscaping. When the results of such characterizations are interpreted in terms of specular reflection losses incurred during interzone transmission, the sufficient conditions for adequate interzone speech privacy beneath flat ceilings can be stated concisely in terms of material properties and the characteristics of a synthetic background-noise distribution system. Certain of the practical ramifications and logical extensions of this treatment of landscape acoustics are also discussed.