Overview
Compared to the classical methods to measure sound transmission loss and absorption of noise barriers in the laboratory, the new Adrienne procedure (European standard prENV 1793-5) has some important advantages. Meanwhile there exists a first commercial implementation of the method. Some preliminary results found with the new method are documented in the literature but a profound experience to introduce the method is still missing. Within this project a series of known noise barriers will be examined with Adrienne. By comparison with the data from the classical measurements in the lab, the correlation between the two methods will be determined. In addition a tool will be developed to translate data found in the laboratory and with Adrienne.
Using prENV 1793-5 (Adrienne) there exists a draft of a European standard for the in-situ measurement of acoustical properties of noise barriers. The aim of the project is testing and validation of the new procedure.
Using comparison of Adrienne measurement results with data found in the laboratory with classical methods at identical structures, a tool will be developed to translate the measurement data from one method to the other.
A checklist will be developed to specify which measurement method is well suited for what kind of structures.
Comparative measurements with two methods, correlation studies
Funding
Results
The acoustical quality of noise barrier materials and constructions can be characterised by transmission loss and absorption. For these quantities standardised measurement procedures in the laboratory are available. However with the Technical Specification CEN/TS 1793-5 (Adrienne) a method was proposed that allows for investigation of transmission loss and absorption in-situ. The advantages of such a field-technique are the possibility to verify the true efficiency of noise barriers and the fact that more appropriate sound incidence directions are used compared to the diffuse field in the laboratory. The Adrienne method is based on the excitation of the object under investigation by a loudspeaker and evaluation of the transmitted and reflected sound waves by microphones. For that purpose impulse responses are measured that allow for time windowing of the components of interest. It is crucial to know the distances between loudspeaker and barrier and barrier and microphone exactly in order to apply an appropriate scaling for geometrical spreading. For low frequencies the method shows principal physical limitations due to the inherent assumption of infinitely large reflector areas and the maximum allowable length of the time window. The method was applied to a variety of noise barriers of different constructions at different sites. The results showed considerable uncertainties that can be traced back to the problem of not well defined distance parameters in case of barriers with significant depth structures and to the large sensitivity regarding the position of the Adrienne time window. Some low frequency results were even meaningless from a physical point of view. For some items data from the laboratory could be compared with in-situ measurements. It was found that both methods show similar tendencies but no meaningful regression analysis was possible due to the large scattering of the results. From a today’s perspective the Adrienne method cannot be recommended for practical use in the context of noise barriers. This finding coincides with newer international experiences that lead to an initiation of a follow-up project Adrienne II on a European level.