Impact Sound Pressure Level Research Articles

The prediction of the vibration reduction index Kij for brick and concrete rigid junctions

Abstract The vibration reduction index, K ij , is related to the transmission of the vibrational power over a junction between structural elements. Two empirical models are proposed to evaluate K ij , on the basis of statistical evaluations of numerous in-field tests carried out on rigid junctions between floors made by concrete beams and ribbed slab with brick blocks and brickwork walls, a type of junction that is frequently encountered in Southern European and Mediterranean buildings. These models can be applied in order to calculate the sound insulation properties, such as the normalized impact sound pressure level, L n ′ , and the apparent sound reduction index, R ′, of walls and floors in buildings. The first model allows the single number value of the vibration sound reduction index of a junction to be calculated, on the basis of the real properties of the materials that constitute the junction. A new quantity, the “essential” mass per unit area, was introduced to implement the model. The second model provides an estimation of the K ij as a function of frequency, subdivided between BB-junction, as ribbed slab with brick blocks floor–brick wall, and CB-junction, i.e. concrete beam–brick wall.

The Testing and Application Methods of the Reduction of Impact Sound Pressure Level by Floor Coverings

The Testing and Application Methods of the Reduction of Impact Sound Pressure Level by Floor Coverings

Subjective evaluation of heavy-weight floor impact sounds in relation to spatial characteristics

This study investigated the effect of a spatial factor, the magnitude of interaural cross-correlation (IACC) function, on subjective responses to heavy-weight floor impact sounds. Heavy-weight impact sounds were generated by a heavy/soft impact source (impact ball) in real apartments, so that impact sound pressure levels (SPLs) (L(Amax)) and IACC could be analyzed. Just noticeable differences (JNDs) of impact SPL and IACC were investigated through the use of impact ball sounds. JNDs were determined by the criteria of 75% correct answers by participants, and it was found that JNDs of impact SPL and IACC were around 1.5 dB and 0.12-0.13, respectively. In addition, the annoyance caused by an impact ball was evaluated by changes in these two parameters. The results show that annoyance increased with increasing impact SPL and with decreasing IACC; the contributions of the two parameters to the scale value of annoyance were 79.3% and 20.4%, respectively. This indicates that the effects of IACC should be considered for the evaluation of annoyance, and the subjective response to impact ball sounds can be improved by controlling IACC, as well as impact SPL.

Can Screening Measurements of Building Insulation Be Made Easier and More Convenient?

Noise complaints in New Zealand suggest that multi-family domestic buildings are not providing for the sound insulation needs associated with modern ways of living. We argue that verification measurements should be more widely encouraged. The research described is aimed at developing screening techniques which are convenient and easy to carry out. The approach is to reduce measurement effort by minimising the amount and weight of equipment needed. It is demonstrated that airborne measurements are possible without using a loudspeaker source – for example using a tapping machine on a “radiation” box. Also it is shown that impact insulation can, in principle, be predicted from airborne insulation measurements alone i.e. without the use of a tapping machine. This requires a library of ‘corrections' factors. Values for some typical floor constructions and coverings are presented. Finally we demonstrate that a lightweight, single hammer, tapping machine can satisfactorily measure standardised impact sound pressure levels.

Room requirements for laboratory measurement of transmission loss and impact sound insulation.

Laboratory measurement of transmission loss (ASTM E90) and impact sound insulation (ASTM E492) have one thing in common: measurement of the sound power radiated into the receive room by the specimen under test. In E90 the reported quantity, transmission loss (TL), is the difference between the incident and transmitted sound power, whereas for E492 the reported quantity, normalized impact sound pressure level (NISPL), is a direct measure of the radiated sound power of the floor. A derivation of the TL and NISPL equations using a statistical energy analysis (SEA) framework shows that the ASTM equations are based on the assumption of power balance and statistical sampling of the sound field. This SEA framework is used to define the acoustical conditions of the receive room (number of modes in each frequency band, the average loss factor in each band, and hence the modal overlap factor), which are then related to the physical properties such as room shape, volume, absorption, etc. The conditions necessary for...

Impedance of standard impact sources and their effect on impact sound pressure level of floors

This paper reports on a systematic study of the Impact Sound Pressure Level (ISPL) due to different standard sources (ISO hammer box, Ball, and "Bang Machine") when applied to a wood-joist floor-ceiling construction with and without various floor toppings. Mea-surement data show that for each floor, the ISPL was different for each source. Not surprising since the blocked force for each source is different. But, after applying corrections for the applied force the ISPL's remain different, suggesting problems since the sources simulate the same human walking activity. Perhaps more importantly, the rank of topping effectiveness (which is simply the difference in ISPL with and without the topping) was different for the three sources. Measurements of the drive point impedance of sources and floors are presented to explain this behaviour and to recognise that the power injected is not just related to the applied force, but also a function the impedance match (or miss-match) between the source and floor. The paper shows using a simple model, it is possible to predict ISPL's for any source if the forces and impedances are known, and using this model floor treatment effectiveness can be correctly ranked by each of the three standardised sources.

Effect of the frequency spectrum trend on the determination of the weighted normalized impact sound pressure level for floor structures

The most common floor constructions in Italian buildings are composed of two parts: the structural one, made of concrete beams and perforated bricks, and the floating floor. The results of the in situ measurements of the impact sound pressure level, realized on the structural part of the floors, show a frequency spectrum trend that increases with the frequency. The spectrum is also characterized by many peaks and dips at the high frequency range that strongly influence the determination of the weighted normalized impact sound pressure level, also for structures with similar mass and geometry. The frequency trend of the beam and brick structures is completely different from the characteristic spectrum of homogeneous concrete slabs or lightweight structures. Considerations on how those differences can influence the obtainable results in terms of the reduction of impact sound pressure level referred to the same floating floor typology, the spectrum adaptation terms and the other acoustic quantities described...

Methods to control low frequency impact noise in wood-frame construction

The control of low frequency impact noise is of great importance in Japan and Korea. For impact noise rating, both countries use standardised heavy and soft impactors that inject high levels of low frequency power into a wood-frame floor due to the high force applied and “good” impedance match between the source and the floor. This paper reports on a parametric study designed to confirm the important parameters for controlling low frequency impact noise and how these parameters are affected by changes to construction details. The paper shows that increasing the drive point impedance floor surface while minimising the structural coupling between the gypsum board ceiling and the structural framing (joists) are important elements. Additionally, a well-designed floor topping can be very effective when applied to a suitable floor. The paper presents data to show the relative importance of direct and flanking transmission paths. Furthermore, it is shown that repeated impacts by the Bang Machine physically change the floor assembly and as a consequence resulting impact sound pressure levels in the receive room also change. The paper concludes with a general discussion and recommendations.

Vibration reduction of thermal break balcony connections

In energy efficient buildings concrete balconies have to be thermally insulated from the concrete floor to reduce heat loss and to increase surface temperature. This thermal break is obtained by polystyrene in combination with high-strength concrete thrust-force bearings and an arrangement of stainless steel straight and bent bars to act as tension and shear reinforcement. The acoustic performance of such thermal break units was investigated under laboratory conditions. Therefore the vibration level difference at different junctions between balcony and the thermal isolated concrete floor as well as the normalized impact sound pressure level of the floor when the balcony is excited with the standard tapping machine are measured. The influence of the number of tension and shear steel bars and the type of thermal insulating material was studied on typical sized balconies connected to small test floors. The vibration isolation at low frequencies was determined using modal testing.

Changed sound properties due to minor construction changes in a lightweight building

This paper relates to building acoustic measurement inside a two‐story office house. The construction, which is known as lightweight, is prefabricated in volumes at a factory and is then transported to the building yard for assembling. It is build up of a wooden frame with particle boards and plaster boards attached. The building consists of a number of nominally, or almost nominally, identical rooms with assumed identical sound properties. In the projection stage, the construction was slightly modified in some of the rooms in order to see in what way the sound properties would be affected. In total eight impact sound pressure level measurements and eight sound reduction index measurements were performed and analysed for the different setups.

Prediction of the impact sound transmission from lightweight stairs in buildings based on a simplified laboratory characterisation

Based on a simplified laboratory characterisation of lightweight stairs the normalized impact sound pressure level in buildings can be predicted using parts of EN 12354. For the characterisation an approach is followed where the stair is treated as an active component with respect to an external excitation (e.g. by the tapping machine). The laboratory characterisation was performed for a timber stair and the normalized impact sound pressure level was predicted for different building situations. The various transmission paths via the separating and flanking walls were investigated and compared to the prediction according to EN 12354. Within the presentation the proceeding will be outlined and the restrictions are discussed. By comparison of measured and calculated values some references for the accuracy of the method are obtained.

Development of a two-parameter system for evaluating impact noise insulation

Impact insulation is currently described with a single number metric impact insulation class (IIC), which correlates poorly with subjective reaction and does not often properly rank order acoustical performance of assembly components. Modifications to IIC have been proposed, but the methods are limited to changing the source or the metric. Experience indicates that impact noise can be divided into two broad classes: Low frequency thudding (e.g., footfalls) and mid/high frequency noise (e.g., heel clicks, dragging furniture, etc.). Low-frequency impact sound pressure level (ISPL) is generally influenced by different variables than the mid/high-frequency ISPL; the authors propose that the two are largely independent. Therefore, two domains are required to adequately characterize the impact noise insulation of an assembly [LoVerde and Dong, 33rd Inter-Noise Proceedings Paper 296, 167 (2004)]. A variety of candidate two-domain systems have been reviewed, where one domain describes the low-frequency performance and the second domain the mid/high-frequency performance [LoVerde and Dong, 14th International Congress Sound and Vibration Paper 476 (2007)]. The two domains are calculated using third-octave ISPL data obtained from recent field impact noise tests. The results suggest that a two-domain system offers considerable improvement over current single-number metrics for evaluating and designing assemblies.

Evaluation of field impact sound pressure levels as a function of tapping machine location

Field impact sound insulation in the United States is typically quantified in terms of field impact insulation class, which is defined in ASTM E1007. This standard requires averaging the receiving room impact sound pressure levels (ISPL) generated by the tapping machine in four defined positions. In a previous paper [LoVerde and Dong, J. Acoust. Soc. Am. 121, 3113 (2007)] the authors analyzed several hundred field tests to determine effects of reducing the number of tapping machine positions on the FIIC rating. In this paper the analysis is extended to look at the detailed effects on the third-octave band ISPL, which may impact design decisions more than the overall FIIC rating. The effect of reducing the number of positions as a function of assembly construction is also examined.

Evaluation of field impact sound pressure levels as a function of tapping machine location

Field impact sound insulation in the United States is typically quantified in terms of Field Impact Insulation Class, which is defined in ASTM E1007. This standard requires averaging the receiving room impact sound pressure levels (ISPL) generated by the tapping machine in four defined positions. To our knowledge the variation in ISPL with different tapping machine positions has not been quantified for field measurements. Hundreds of recent field tests are compiled for a statistically significant analysis of this variation, covering all common floor/ceiling assembly construction types and many different flooring and resilient materials. The effects of reducing the number of tapping machine positions in the ASTM standard on the accuracy and precision of the measurement are evaluated.

Analysis of airborne sound insulation and impact sound pressure level provided by a single partition containing a heterogeneity

This paper studies the acoustic behaviour provided by a single infinite elastic partition dividing an infinite acoustic medium, containing two-dimensional (2D) heterogeneities placed parallel to the layer's surfaces, which simulate the presence of fittings such as pipes. The problem is solved in the frequency domain using the boundary element method (BEM). Only the surfaces of the heterogeneities are discretized, since 2.5D Green's functions for the single layered media, bounded by acoustic media, are used. Time domain responses are also computed by applying a (fast) Fourier transform to the responses obtained in the frequency domain. The heterogeneities are assumed to be either rigid, free, fluid-filled or elastic-filled inclusions. The simulated models are used to study the contribution of the heterogeneities to the final airborne sound insulation and impact sound pressure level provided by a single partition. It was found that both airborne sound insulation and impact sound pressure level may be influenced by the presence of the heterogeneity at higher frequencies.

Evaluation of mid‐ and high‐frequency impact insulation methods

Impact insulation is currently measured using impact insulation class (IIC) and a standard tapping machine described in ASTM E492 and E1007 (and corresponding ISO metrics and standards). The resultant IIC value does not correlate well with subjective reaction. In previous papers, the authors have focused on the low‐frequency thudding from footfalls in lightweight wood construction and shown that the impact sound pressure level (ISPL) in the 63‐Hz octave band correlates better with subjective reaction than IIC or other metrics [LoVerde and Dong, J. Acoust. Soc. Am. 112, 2201 (2002); INCE Inter‐Noise 2004 Proceedings, 167 (2004); J. Acoust. Soc. Am. 119, 3220 (2006)]. Further, the low‐frequency ISPL is controlled by different variables than the mid/high‐frequency ISPL. This suggests that a two‐metric system would be valuable where the first metric describes the low‐frequency performance and the second metric describes the mid/high‐frequency performance. Field testing experience is presented showing that IIC does not adequately differentiate the mid/high‐frequency performance of various resilient materials. Candidate mid/high‐frequency metrics are evaluated to determine if any result in improved methods for evaluation and rank‐ordering of floor/ceiling assemblies.

Heavy and light impact sources to rate impact sound transmission and changes due to applied floor toppings

The magnitude and spectrum of the power injected by an impact source depends on the impedance of the source and floor. If standardized impact tests are meant to give ratings that correlate well with subjective impressions of footstep noise, it follows that the impact source used should have the same impedance as an average human foot at least over the range of test frequencies. The ISO tapping machine, the Japanese tire machine, and an 18‐cm‐diam rubber ball do not satisfy this criterion. Consequently, their impact spectra differ from those from a live walker. Floor toppings, in particular, are ranked differently. Examples of discrepancies will be presented for direct transmission between vertically separated rooms. For horizontally and diagonally separated rooms, flanking transmission controls the impact sound pressure level. The sound pressure level depends not only on the power injected by the source, but also source location relative to the flanking junction because of propagation attenuation across the floor. Sensitivity to source location is similar for different sources (ISO tapping machine and Japanese ball), suggesting that the same source could be used for direct and flanking transmission measurements if the source adequately simulates the impedance of a human foot.

Technical Note: Controlling the Impact Sound Insulation of Concrete Slab Floors

This paper investigates the impact sound attenuation of a concrete slab floor with different covering as topping layers. The basic covering is an extruded polystyrene foam board, reinforced with fiberglass mat and painted with special cementatious mortar. The concrete slab floor was tested with extruded polystyrene foam board of different thicknesses, foam board with thin rubber surfaces, and foam board with a thin rubber layer adhered to ceramic or vinyl tiles. Also, multi layers of extruded polystyrene foam board have been tested as a topping to the tested floor. The weighted normalized impact sound pressure level and weighted reduction of impact sound pressure level have been determined and used for comparison between the tested samples.

임펄스응답적분법을 이용한 잔향시간의 측정방법이 규준화 바닥충격음레벨에 미치는 영향

For the evaluation of the normalized impact sound pressure level, the reverberation time of the receiving room should be measured. This paper deals with the effect of the time constant of FFT analyzer and the measuring points on reverberation time. It is found that the time constant should be in the range between 10 ms and 35 ms. While the effect of measuring points on the reverberation time is significant when the bandwidth is narrow it is negligible in the evaluation of the normalized impact sound pressure level.

Estimation of Acoustical Performance of Floating Floors from Dynamic Stiffness of Resilient Layers

This paper describes a procedure for evaluating the reduction in impact sound pressure level of floating floors by measuring the apparent dynamic stiffness of the resilient layer, according to International Standard EN 29052-1. The impact sound pressure level experimental data, obtained according to International Standard UNI EN ISO 140-8, was compared with estimates obtained from dynamic stiffness measurements. Results confirm the effectiveness of the empirical model. Two questions are addressed. The first concerns the decrease in layer thickness over time. The second concerns the relationship between damping ratio and performance.