Klas Hagberg

Subjective and Objective Evaluation of Impact Noise Sources in Wooden Buildings

Multi-storey timber buildings up to 6 and more floors are increasingly built in many European countries. The challenge with these buildings can be that with traditional intermediate floor constructions in timber it can be difficult to fulfill the standard requirements and even when they are met, low frequency transmission can still cause complaints. Additionally it is difficult to develop appropriate light weight floor constructions since it is well known that the correlation between the standardized evaluation methods using the tapping machine and the human perception of impact noise can be poor, especially in buildings with light weight structures. In the AcuWood project, measurements and recordings on different intermediate timber floor constructions in the laboratory and the field were performed covering a wide range of modern intermediate timber floor constructions. Additionally, one intermediate concrete floor with different floor coverings was included in the study. Besides the standardized tapping machine, the modified tapping machine and the Japanese rubber ball and “real” sources were employed. Subjective ratings from listening tests were correlated to many technical single number descriptors including the standardized descriptors and non-standardized proposals. It was found that the Japanese rubber ball represents walking noise in its characteristics and spectrum best, taking into account the practical requirement of a strong enough excitation for building measurements. The standardized tapping machine, with an appropriate single number descriptor, L′nT,w + CI,50-2500 or slightly better, L′nT,w Hagberg 03, leads also to an acceptably high determination coefficient between the descriptor and the subjective ratings. Additionally, the study delivered data, from which proposals for requirements for the suggested single number ratings are deduced, based on the subjective ratings.

Evaluating Field Measurements of Impact Sound

Analyzing data from an earlier investigation revealed uncertainties concerning data evaluation. Therefore, data points comprising 1/3-octave impact sound data and interview data from the earlier investigation are partly replaced by new data points. The data removed pertain to horizontal measurements. The investigation is then completed with data for 10 new housing units pertaining to vertical impact sound measurements. Including the new floor structures, a total number of 22 vertical data points are included. It was found that the current international standard method is unsatisfactory, and that the single-number value proposed in the earlier investigation suffers from shortcomings: when analyzing the new data sample, the correlation coefficient fell from 87% to 83%. The best choice proved to be a reference curve with a steep positive slope of 5.5 dB/octave between 50–100 Hz and the curve becomes a straight line. This reference curve resulted in a correlation coefficient again equal to 87%.

Impact sound insulation of wooden joist constructions: Collection of laboratory measurements and trend analysis:

Wooden building systems are becoming more common. Still, there are a huge variety of floor assemblies in the market. The floor assemblies normally become the weakest part due to impact load from walking persons. So far, there are no reliable standardized calculation models available regarding prediction of impact sound in the entire frequency range. Therefore, the design is always based upon previous experiences and available measurements. For the development of prediction models, the first approach is to carry out a grouping of various available floor assemblies. From that, the aim is to trace similarities and carry out simplifications. Correlation is found between the single number L nT , w ′ + C I , 50 - 2500 and the mass per unit area. It is also found that the ceiling system is useful in order to optimize the construction. The data will be further processed and used in the model development and to propose optimization of wooden floor assemblies.

The furniture industry needs a new evaluation standard for evaluation of sound absorption

Since decades the standard ISO 11654 are prevailing for evaluating sound absorption of products. The standard is developed and fully adapted to ceiling manufacturer, in particular mineral wool ceiling manufacturer. However, the standard is used independently of which interior product it is applied to, casing a lot of “misuse” and confusion amongst many manufacturer. In particular, when it comes to evaluation of various types of office screens, the ISO 11654 becomes a problem. There is no need, and probably not even possible, to calculate absorption factor for an office screen correctly. Therefore, Sweden decided to develop a new standard, SS 25269—“Acoustics—Evaluation of sound absorption of single objects.” Hence office screens should be treated as single objects to cover a wide range of variety. The standard specifies an evaluation method of the sound absorption using only sound absorption area for each object tested. It will simplify the evaluation and minimize risk for errors since there is no need to...

Sound Insulation Descriptors in Europe—Special Rules Complicate Harmonization within Lightweight Industry

Many European countries have a sound classification standard connected to the building regulations in order to specify minimum requirements. The various national standards have a lot of similarities, however the acoustic descriptors differ more than what is obvious by a quick comparison of current classification standards. The different descriptors in each country are to some extent a heritage from the past, successively adapted to the building industry in each country and their certain traditions in building technique. The descriptors and the requirements are necessarily not based on subjective experience. Furthermore, to fulfil national interests and to fit to new design trends of housing units etc, the descriptors involve small local adaptations to each country. These local adaptations are not easy to find unless the standards are read carefully. This causes problem since the building industry is not restricted to national boundaries anymore. Many companies have activity in countries adjacent to each other and in future the probability for increased activity all across Europe and also outside Europe is to be expected, unless regulations restrict this development. Combining national special rules and some severe uncertainties in the measurement and evaluation procedures of sound insulation, the situation is more critical for lightweight structures. This is partly due to the fact that the development of building systems are made in one country, the production takes place in production plants, i.e. the production and the process are fitted to local regulations and are “standardized”. The standardized process is fast and dry but also needed due to lack of prediction models. And once the light weight system and the system process are established in one country it is complicated and expensive to adapt them to other countries. In this paper an overview of special national rules in some European countries and major problems connected to lightweight construction are presented.

A Handbook on the Management of Acoustic Issues During the Building Process

A new handbook has been published by the Swedish National Board of Housing, Building and Planning. This handbook describes the building process from an acoustical point of view. It focuses on the conversion of functional requirements on the performance of the building to appropriate designs of a building. This type of requirement allows all kinds of solutions to be applied, but is also requires coordination of acoustic issues between the parties involved during the entire building process. Hence, the handbook addresses detailed information to each party. Functional requirements and acoustic issues are complex by nature, because they affect many building elements, they are handled by several parties and they must be considered during several phases of the building process. Typical errors come from building designs (floor plans), product designs (input data of elements), calculation models, quality of workmanship (during the construction phase) and uncertainties in field measurements. The aim is to help the commissioner manage the responsibility for these issues. The handbook also covers a large field of practical applications to support the acoustic expertise. It is expected that this handbook will encourage developers and contractors to deal with acoustic issues more efficiently. If the noise environment is not considered in the design process for new residential areas and other building facilities, the satisfaction of tenants, the health costs for the society and the building values will be affected. If verifications are made only at a late stage of the building process, errors are normally discovered too late. They are then expensive to correct for and it is difficult to find out who is responsible. When the verifications are made effectively during the process, costs are minimized.