Estimates of mobility for prediction of structure-borne sound transmission in buildings

This paper aims to provide a practical approach to the prediction of structure-borne sound power of mechanical installations in buildings. For structure-borne power, two source quantities, activity and mobility, are required, in combination with one receiver quantity, the receiver mobility. The source activity, in the form of free velocity or blocked force, is usually measured. For source mobility and receiver mobility, estimates, based on simple expressions, can provide a useful starting point. Also, machine bases may be categorised as: compact, plate-like, flanged or framed. Receiver structures, floors and walls, may be categorised as: plate-like, ribbed plate or framed plate. The estimates of source mobility are based on the rigid body value, the characteristic plate mobility and the fundamental plate frequency. For ribbed and framed plate structures, the mobility will vary with location, but again simple estimates of mobility, based on characteristic values and distance from the ribs, are possible

Uncertainties in the Two-Stage Reception Plate Method for Source Characterisation and Prediction of Structure-Borne Sound Power

To obtain the transmitted structure-borne power from a vibrating machine into a supporting/connected structure, three quantities are required in some form: source activity (either the free velocity or the blocked force), source mobility and receiver mobility. The three quantities can be measured directly, or indirectly using a reception plate method. Whilst direct measurements can be precise, they require extensive data acquisition and processing. The reception plate method is simpler and less precise and therefore yields an engineering grade of accuracy. This paper reports on a collaborative investigation, towards developing an industrial standard for source characterization using the reception plate method. The method yields data as frequency band-averaged values and also as equivalent single values. These simplifications result in uncertainties when obtaining the source quantities and therefore in predictions of the structure-borne sound power in installed conditions. The causes of these uncertainties are considered

Effect of steam exploded treatment on the reactivity of pine wood

A commercial thermally treated biomass process known as ‘steam exploded biomass’ provided the treated biomass samples for this project together with the original yellow pine wood. The aim was to investigate the change in pulverised biomass reactivity. The steam exploded biomass is processed into pellets in the normal way and are known as black pellets (BP). The material was investigated using the Hartmann dust explosibility equipment. This enables the minimum explosion concentration (MEC) to be determined together with the initial rate of pressure rise and the flame speed and these latter parameters are measures of the mixture reactivity. BP was found to have a higher reactivity than the raw biomass with a much leaner MEC. A good correlation was found between the initial rate of pressure rise and the flame speed for the raw wood sample. Surface morphology was performed to investigate the effects of the steam exploded treatment. This showed the enhancement of the proportion of fines. The particle size distribution was determined and this confirmed the enhancement of the fineness of the treated sample. The enhanced reactivity of BP was found to be due to the greater proportion of fine particles which had a higher heating rate and a greater release of volatiles. The steam explosion treatment was found to be an effective pre-treatment in facilitating the combustion of renewable fuel and the main effect was that it was more easily milled, changes in the biomass chemistry was of secondary importance