No abstract

Steel studs are used in double walls to provide structural stability. This creates a vibration transmission path between leaves that can often be more critical than the airborne path through the cavity. Some of the existing models for sound transmission consider the studs as elastic springs. The spring stiffness may be taken as the cross-section elastic stiffness of the stud, but this leads to an underestimation of the vibration transmission. A procedure to obtain more accurate parameters to be used in vibration and sound insulation models is presented. The results show that they must be obtained from dynamic models and/or experiments.

The present paper provides a modification of near-field acoustical holography (NAH) enabling reconstruction of sound fields in a room in order to study plane structures radiating in enclosed spaces; the new technique is called phonoscopy. A description of the measurement laboratory is given; a single microphone scanner is used to measure the pressure on the hologram plane. Three examples of measurement are presented: a point source located on a rigid wall, a homogeneous wall, and a window mounted in a wall. Maps of the velocity of the structure and of the acoustic intensity radiated are given. The accuracy of phonoscopy is demonstrated by comparison with the accelerometer methods (for measuring vibration velocities) and the two-microphone technique (for measuring acoustic intensities). Some K-space spectra are also presented and analyzed, giving more information about the physics of the vibrator.

When building elements of wood-frame lightweight constructions are considered, laboratory acoustic measurement methods have to be rethought. Indeed, because lightweight elements are often highly damped, the vibrational fields are no longer reverberant and existing standards often lose relevance, particularly in the case of mechanical excitation (such as in impact noise measurements or in vibration reduction index measurements of junctions). In this paper, standardized methods are identified or new methods are proposed for characterizing lightweight elements in order to obtain input data for prediction models such as that adapted from the standards EN 12354-1 and-2 and described in a companion paper. Moreover, it is shown that a new parameter (the radiation efficiency) is required when predicting the performance of lightweight buildings. Measurement results are shown for both wall and floor elements and the results are discussed, particularly in comparison with heavy building elements.

When wood frame lightweight constructions are considered, both the standardized methods, EN 12354-1 and-2, for predicting building performances from the performances of building elements and the related standardized laboratory measurement methods for characterizing building elements and their junctions have to be reconsidered. In this paper, a prediction method based on Statistical Energy Analysis and adapted to lightweight constructions, is presented. It was applied to a two-storey four-room building where an analysis of the different transmission paths was required in order to understand and improve the acoustic performances of the building. Comparisons between results, expressed in terms of airborne and impact sound insulation between rooms, either directly measured or calculated using the prediction method, are given in the three cases of vertical, horizontal and diagonal transmission. A satisfactory agreement between calculated and measured results is obtained.