It summarizes the application of the intensity method LQ VLWX for locating flanking sound transmission paths in buildings. Warnock19 investigated the influence of the test frame on the measured SRI of a plasterboard wall. To calculate the intensity, the pressure is determined by averaging the two microphone signals with (SA+SB)/2.
The validity of the sound intensity measurement is described by the pressure-intensity indicator, )pI,. It determined the influence of the waiting room reverberation time on the measured SRI. The second advantage was that the intensity radiated from different parts of the panel could be determined.
The disadvantages of the intensity method were that the measurement technique makes stricter demands on the users and the equipment. Adjusting the balance between the sound pressure channels in the source room and the two channels of the intensity probe also causes extra work. The pressure method is currently more popular and the results of the intensity method are corrected.
In this method, the back wall of the receiving chamber is strongly absorbent and the incident sound power in the vicinity of the sample is determined with the help of the sound pressure.
Several studies have been published on the prediction of sound insulation of double-walled structures. Immediately after this, London78 presented the progressive wave model, where the influence of the angle of incidence of the sound is taken into account. The transmission of sound between the plates was divided into two paths: through the air path (cavity coupling) and sound bridges (structural coupling).
The benefit of these designs was that the lowest normal mode of the panel was considered. The cavity absorption coefficient was used to describe the losses in the cavity. Davy also studied the behavior of SRI in mass-air-mass resonance for oblique angles of sound incidence θ.
In the following, an overview of the literature regarding the influence of different physical parameters on the SRI of double panels will be presented. In the case of symmetrical modes, the critical frequency depends on the bending stiffness of the entire sandwich panel. Sound-absorbing linings on the front of the wall have been investigated in some texts.
The influence of lining on the SRI depended on the flow resistance and thickness of the absorbent. The application of the sound intensity method in laboratory and field conditions, especially in the presence of strong flanking sound. It was shown that the contribution of )pI, determined by the properties of the sound field, could be predicted by [IV].
This could also be proven in the laboratory by measuring the carpet's dynamic stiffness. The advantages of the intensity method have also been obvious in several similar cases.1. The calculation of the intensity measurement error required the determination of three parameters: the absorption area of the sample, the absorption area of the receiving room and the flanking ratio, i.e. the ratio between sound energies radiated by flanking surfaces and sample, respectively.
The influence of the aspect ratio and suction of the waiting chamber on )pI was studied experimentally for several specimens [IV]. The crack and adhesive transmission coefficient is greater for the free crack.
If the original surface area of the gaps had been used, the total SRI of the door would have been greatly underestimated. In publication [III], the area of the sealed gaps was estimated based on the best fit between the measurement and prediction result. The area was usually significantly smaller than that of the physical area of the fissure.
The major advantage of the Mechel model is that the area of the slit is based on the area of the slit. The disadvantage is that measuring the impedance of the kit is necessary, making the model less practical. &21&/86,216. According to the literature, this is the main disadvantage of the intensity method compared to the pressure method.
Thus, the only significant advantage of the LQ VLWX intensity method is the ability to localize the source. This model assumes knowledge of the impedance and spread factor of the gaskets. The total SRI of the door can be calculated using the surface-weighted transmission coefficients of the door leaf and slots.
The verifying measurements must be carried out in standard conditions and the physical parameters of the wall must be carefully determined and documented. According to the above conclusion, none of the existing double panel prediction models were applicable to all types of double wall structures. The existence of the normal modes of the subpanels formed between the studs must also be considered.
Finally, the use of the Paris equation for the calculation of the sound transmission coefficient with ground incidence should be reconsidered. The measured intensity level, /I, depends on the true sound intensity level, /I, and the residual intensity level, /I,R. Residual intensity is a consequence of the phase mismatch of the intensity measuring device. The measured pressure-intensity index, )pI, is always slightly less than )pI due to the influence of residual intensity.
13 ASTM E-90-90 Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions, The American Society for Testing and Materials, Philadephia, USA, 1990. Minten, Comparative study between the sound intensity method and the conventional two-chamber method to measure the sound transmission loss of wall constructions to calculate, Noise Con. Sauer, The effect of some physical parameters on the laboratory measurements of sound transmission loss, Appl.
Cops, Acoustic intensity measurements and their application to panel and wall sound transmission loss, Proceedings of Internoise. Myncke, Effect of sound transmission room design on sound transmission glass loss - Intensity versus conventional method, Noise Con. Jacobsen, Is there systematic disagreement between intensity- and pressure-based sound transmission sound loss measurements.
Qi, Measurements of sound transmission loss using the sound intensity technique - Part 1: The effects of reverberation time, Appl. Rindel, Prediction of sound transmission through thick and rigid panels, Proceedings of The Institute of Acoustics. Tachibana, Sound transmission loss analysis of multiple structures by four-terminal network theory, Proceedings of Internoise 85, Munich, Germany, 18-20. Sept.
Wang, The effect of flexible connection on the sound transmission loss of double metal-studded plasterboard partitions, China J. Loney, The effect of cavity absorption on the sound transmission loss of steel-studded gypsum board partitions, J. Narang, Effect of fiberglass density and resistance to flow on sound loss in plasterboard walls, Noise Con.
Warnock, Influence of sound absorbing material, stud type and spacing and screw spacing on sound transmission through double panel wall test, Proceedings of Internoise 93, Leuven, Belgium, August. Kim, Prediction of sound transmission loss through multilayer panels using Gaussian distribution of directional incident energy, J. Zhao, Measurement of the sound transmission loss of circular and slit-shaped openings in finite thickness rigid walls by intensimetry, J.