There is a need to develop single number quantities (SNQ) of impact sound insulation that correlate better with walking sound annoyance. Previous research has indicated that impact sound insulation should be evaluated from 20 Hz in lightweight constructions, using modified spectrum adaptation terms. The purpose of our study was to verify whether frequencies between 20 and 50 Hz are important for perceived walking sound annoyance and to verify whether the proposed spectrum adaptation terms improve correlation with perceived walking sound annoyance. Binaural recordings of walking sound in one heavy and one lightweight construction were evaluated in a two-part listening test. The need to include frequencies from 20 Hz when evaluating lightweight constructions was verified. Both tested constructions achieved similar performance in terms of L^′_nT,w and L^′_nT,w + C_I,50-2500, while a significant mismatch in the rated annoyance was observed. The correlation between SNQ and subjective response was considerably improved, when the impact sound insulation was evaluated from 20 or 25 Hz using a flat frequency-weighting factor.

A previous Swedish research project indicated the potential need for evaluating impact sound insulation from 20 Hz in buildings with lightweight constructions. This is a discrepancy compared to the commonly used frequency intervals starting from 50 or 100 Hz. The statistical significance of this groundbreaking suggestion was however not satisfactorily strong since the result was based upon a limited number of building objects.

The scope of the present paper is to secure the previous study by adding additional objects to the underlying database, thereby increasing the confidence of the results. The methodology is to perform impact sound insulation measurements in apartment buildings of various construction types and to perform questionnaire surveys among the residents. The measured sound insulation is compared to the subjective rating by the occupants in order to find the parameter giving the highest correlation with respect to frequency range and weighting.

The highest correlation was found when the impact sound insulation was evaluated from 25 Hz using a flat frequency-weighting factor. Frequencies below 50 Hz are of great importance when evaluating impact sound insulation in lightweight constructions

In order to reduce costly downtime, adequate condition monitoring of the automatic transmission components in heavy duty construction equipment is necessary. The transmission in such equipment enables to change the gear ratio automatically. Further, the bearings in an automatic transmission provide low friction support to its rotating parts and act as an interface separating stationary from rotating components. Wear or other bearing faults may lead to an increase in energy consumption as well as failure of other related components in the automatic transmission, and thus costly downtime. In this study, different sensor data (particularly vibration) was collected on the automatic transmission during controlled test cycles in an automatic transmission test rig to enable adequate condition monitoring.

An analysis of the measured vibration data was carried out using signal processing methods. The results indicate that predictive maintenance information related to the automatic transmission bearings may be extracted from vibrations measured on an automatic transmission. This information may be used for early fault detection, thus improving uptime and availability of heavy duty construction equipment.

The relevance of performing reverberation time measurements at very low frequencies became an issue in Sweden when the national standard recommended that impact sound insulation should be evaluated from 20 Hz for sound classes above the minimum requirement. Even though the standard states that L'_n,T is not to be normalized with respect of reverberation time for frequencies below 50 Hz, it could be argued to include such a correction term to handle any possible variation in the absorption properties of the room. But this can be done only if the reverberation time can be accomplished with reasonable accuracy. The present paper presents an empirical study where reverberation time has been measured from 20 Hz in two different bedrooms with more than 100 microphone positions in each in order to determine the spatial variation. A comparison is made between the uncertainty as a function of frequency and it is indicated that the standard deviation is larger for the lowest frequencies, below 50 Hz, compared to higher. From an engineering point of view, this can be compensated by adding additional positions to the already existing ISO measurement procedure

There is a strong trend to industrially produce multi-storey light weight timber based houses. The concept allows the buildings to be manufactured to a more or less prefabricated extent. Most common types are volume/room modules or flat wall and floor modules. When assembling the modules at the building site, elastomer isolators are used in several constructions to reduce flanking transmission. The sound insulation demands in the Nordic countries are relatively high and therefore the flanking transmission must be well controlled, where elastomer isolators are an established alternative. Decoupled shielding wall elements is another. There are though no working studies or mathematical models of the performance of these isolators. They are treated as simple mass-springs systems that operate vertically, i.e. one degree of freedom. In this paper there are analyses of an expanded set of experimental data of the structure borne sound isolating performance of elastomer isolators, which are separating an excited floor from receiving walls. This part II study now includes all in all 9 buildings. The isolation performance dependence on structure type is analyzed. An empirically based regression model of the vibration level difference is derived. The model is based on measurements of 8 elastomer field installations, which are compared to an installation without elastomers. A goal is that the data can be used for input in future SEN prediction models for modeling of the flanking transmission part of sound insulation

Measuring reverberation time is normally one of the steps within the procedure of determining sound insulation in dwellings where 100 or 50 Hz usually serves as the lower frequency limit. However, even lower frequencies have become a matter of interest as research in the field recently indicated that the range 20-50 Hz seems to be of great importance when it comes to the perception of impact sound in lightweight buildings. A major issue in this context is then whether it is appropriate to measure and evaluate reverberation time at such low frequencies. This paper presents an empirical study of reverberation time measurements made in two rooms using more than 100 microphone positions in each. The measurement uncertainty with respect to microphone position and combinations of positions are compared for the frequency bands from 16 to 1600 Hz. Furthermore, it is analyzed how many microphone positions are needed in order to, with a reasonable probability, end up with an uncertainty in the related standardized impact sound level insulation L′_n,T within ±1 dB

Traditionally, multi-family houses have been constructed using heavy, homogenous materials like concrete and masonry. But as a consequence of the progress of lightweight building systems during the last decades, it has been questioned whether standardized sound insulation evaluation methods still are appropriate.An extensive measurement template has been applied in a field survey where several vibrational and acoustical parameters were determined in ten Swedish buildings of various constructions. In the same buildings, the occupants were asked to rate the perceived annoyance from a variety of natural sound sources. The highest annoyance score concerned impact sounds, mainly in the buildings with lightweight floors.Statistical analyses between the measured parameters and the subjective ratings revealed a useful correlation between the rated airborne sound insulation and Rw′+C50–3150 while the correlation between the rated impact sound insulation and Ln,w′+CI,50–2500 was weak. The latter correlation was considerably improved when the spectrum adaptation term with an extended frequency range starting from 20 Hz was applied. This suggests that frequencies below 50 Hz should be considered when evaluating impact sound in lightweight buildings.

To obtain satisfactory sound insulation is a challenging task when designing lightweight buildings. Poor performance at low frequencies as well as severe flanking transmission has traditionally often been more pronounced compared to heavier constructions. In the present casestudy based paper, various aspects of using elastic layers to improve sound insulation in lightweight buildings are considered.The effect on impact and airborne sound insulation by using two different kinds of vibration insulators between floor plans was examined together with the effect of using glues of various degree of elasticity in the construction. In situ measurements were performed inside a four-storey wooden frame based residential building and statistically significant variations in sound insulation were found.The efficiency of the two vibration insulators was further evaluated by vibration reduction measurements over the junctions. The difference in vibration reduction was found to be nearly constant in the frequency range 50-1000 Hz while the improvement of impact sound insulation increased by frequency.Along term test of elastic glues was also conducted, during three years, for stability over time. The best glues preserved a significantly higher damping ratio over time compared to the main part of the glues.

Various research aspects on sound and vibrations in lightweight buildings are covered by the Swedish research programme AkuLite. One of the most important topics has been to find out to what extent objective measured parameters correlate with subjective opinions from people living in multifamily houses. Typical questions to be pointed out are: Do existing ratings like R'w (+C50-1350) and L'n,w (+CI,50-2500) correlate well enough to the tenants' perception? Can other measureable parameters be found that show better agreement? Are the often used frequency limits of 100Hz or 50Hz low enough? Can any significant differences be seen when comparing lightweight buildings with concrete buildings? Extensive sound and vibration measurements have been performed in numerous buildings of varying construction including lightweight timber or steel based framing, cross laminated timber and concrete. In general frequencies from 20 Hz have been covered. Questionnaires have been distributed to the tenants where they were asked to give their opinion on a number of adequate questions related to sound and/or vibration perception. The results from the measurements and from the questionnaires have then been compiled, followed by a comprehensive statistical analysis in order to see the degree of correlation between them.