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13.02 Impact and Structure-Borne Noise, Part 3

Impact sound pressure values – Field measurements for different configurations of concrete slabs on the ground
Time: 11:20 am

Author: Bernt Mikal Larsen

Abstract ID: 1113

The presentation will summarize and discuss values of field measured normalized impact sound pressure level L'n,w measured sideways with different configurations of concrete slabs on ground within buildings. All results are adjusted to receiving room volume of 100 m3 and with thickness of concrete slab 80-100 mm. Measurement on continuous concrete slab on expanded polystyrene gives L'n,w between adjoining rooms of 74 dB. Different principles of splitting have been investigated to evaluate the effect on L'n,w. The configuration where only the concrete slab is split (and with a plastic film between the concrete base and the upper layer of expanded polystyrene), gives L'n,w of approximately 66 dB which is 8 dB lower than for a continuous bare concrete slab. When both the concrete slab and the upper layer of expanded polystyrene are split, measurements show L'n,w of 58-61 dB for the case of no flooring, which is 13-16 dB lower than for a continuous concrete slab (no split). When both concrete slab and all layers of polystyrene are split down to continuous foundation measurements show L'n,w of 55 dB. The situation with concrete slab and all layers of polystyrene split and with no foundation beneath gives L'n,w of 46 dB. Consequences for airborne sound and R'w will be discussed as well for the above mentioned configurations.

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Impact sound prediction of finite floor structures with the modal transfer matrix method
Time: 9:00 am

Author: Jasper Vastiau

Abstract ID: 1636

The transfer matrix method (TMM) is commonly employed for wave propagation analysis in layered media of fluid, elastic and porous nature. Up to now it has been used extensively to analyze airborne sound transmission and sound absorption. Its use for impact sound transmission has been investigated to a limited extent, i.e. for thick homogeneous elastic plates of infinite extent and for specific receiver points. This contribution aims to broaden the scope such that the global impact sound, radiated by finite floor structures containing elastic, fluid and/or porous layers, can be analyzed in a more robust way than previously available in literature. A disadvantage of the conventional TMM is that only floors of infinite extent can be implemented. It is possible to remove this drawback using a spatial windowing technique. Furthermore, the modal behavior of the floor is approximately taken into account by projecting the impact force onto the mode shapes and only allowing for the propagation of those waves, corresponding to modal wavenumbers, in the structure. Predictions of the radiated sound power are made for various bare floors and floating floor systems of both infinite and finite extent.

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Measuring the force due to standard tapping machine and floor impedance for ASTM standards
Time: 12:20 pm

Author: Sunit Girdhar

Abstract ID: 1644

The standard tapping machine used for the ASTM and ISO tests does not require the test engineer to measure the input force in the system, instead, just relies on measuring the sound pressure level (SPL) output. However, the input force depends on the assembly itself being tested. The input force levels are lower for lightweight assemblies like hardwood floors as compared to heavyweight assemblies like concrete. Without knowledge of this input force, the output SPL levels cannot and should not be compared using the IIC (Impact Insulation Class) rating. In this work, we measured the input force levels for the same tapping machine on different floors. We also measured the floor impedance for different assemblies and their comparison is also shown. This work shows the importance of measuring input forces for the standard floor-ceiling assembly impact tests

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Quantifying sound transmission of building structures for optimization in early-stage design
Time: 4:20 pm

Author: Jonathan Broyles

Abstract ID: 1781

Technological advancements in computational building modeling have enabled designers to conduct many simulations at both the building and component levels. With the evolution of parametric modeling at the early stage of building design, designers can evaluate multiple design options and identify the best performing solutions. However, to conduct design space exploration or optimization, an objective function is needed to evaluate a design’s performance. While defined objectives exist for building design considerations such as sustainability, energy usage, and structural performance there is not a single, encompassing objective that can accurately assess acoustic performance for optimization. This paper proposes the development of a novel acoustic objective function that encompasses sound transmission when designing floors, walls, or other acoustic barriers. The composite function will incorporate both air-borne and structure-borne sound simultaneously to determine the appropriate percentages for the formulation of the composite function. The results of the composite acoustic function for multiple floor constructions will be compared for the determination of a final acoustic transmission composite function. This study will detail why the implementation of a composite acoustic function is valuable for design optimization for sound transmission, what the limitations of this method are, and future applications of a composite acoustic function.

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Countermeasures against floor impact sound by heavy impact source of a box floor structure in a reinforced concrete wall construction testing device
Time: 7:00 pm

Author: Ryuta Tomita

Abstract ID: 1832

We have performed experimental examinations for the purpose of proposing a floor finishing structure with superior effects in terms of combating heavy-weight floor impact sound. We have developed a box floor with ease of construction and excellent heavy-weight floor impact sound insulation performance and examined its effect with a 1200 × 1200 mm test piece connected to inter-noise 2020. The box floor has a floor finishing structure with anti-vibration and sound insulation measures aimed at improving measures against heavy-weight floor impact sound. We herein report the results of a basic examination on the reduction of the transmitted heavy-weight floor impact sound of a box floor structure in a reinforced concrete wall construction testing device when the area is further expanded to about 10 ?. As a result, with the air layer under the box floor open, the floor impact sound level was reduced by 9 dB in the 63-Hz band compared to the bare surface. In addition, with the air layer at the bottom of the BOX floor sealed, the floor impact sound level was reduced by 5 dB in the 63-Hz band compared to the bare surface.

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Simplified parametric modeling to predict vibration attenuation provided by on-grade slabs
Time: 1:20 pm

Author: Steven Lank

Abstract ID: 2033

When measured vibration amplitudes at the proposed site for a highly sensitive facility exceed the maximum allowable for the sensitive equipment, mitigation measures must be integrated into the design that will reduce the vibration amplitudes to meet the requirements.  Past studies have shown that thick concrete slabs supported on a well-engineered subgrade can effectively reduce ground borne vibrations at certain frequencies.  Predicting the vibration performance of a new slab-on-grade can be a significant challenge, however, as the performance is highly dependent upon the site soil conditions and nature of the vibration sources impacting the location, as well as structural characteristics.  Large and detailed three-dimensional finite element analysis models of the site conditions and proposed structure are often used for this type of assessment, however development of such a model requires significant time and cost to develop accurately.  This presentation discusses a proposed an alternative simplified parametric modeling technique using two-dimensional plane strain modeling.  This technique can be utilized in combination with real-world data to predict the relative benefit of various slab thicknesses and design features such as structural breaks.  The paper will include multiple comparisons between predicted results using this methodology and field measurement results.

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Effectiveness of neoprene pad vibration isolators at high frequencies
Time: 1:40 pm

Author: Jerry Lilly

Abstract ID: 2068

The natural frequency, dynamic stiffness, and insertion loss of commercially available neoprene pad vibration isolators have been measured in a simple, single degree of freedom system over a wide range of pad loadings out to a maximum frequency of 10 kHz.  The results reveal that dynamic stiffness can vary significantly with pad loading as well as the durometer of the material.  It will also be shown that insertion loss follows the theoretical single degree of freedom curve only out to a frequency that is about 5 to 10 times the natural frequency, depending upon the pad durometer rating.  Above that frequency wave resonances in the material cause the insertion loss to deteriorate significantly out to a frequency near 1 kHz, above which the insertion loss maintains a relatively constant value, again depending upon the pad durometer rating.  In some instances the insertion loss values can approach 0 dB or even become negative at specific frequencies in the frequency region that is 10 to 20 times the natural frequency of the system.

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Using Inverse Transient Statistical Energy Analysis to determine the transient power input from a heavy impact on floating floors
Time: 8:00 pm

Author: Hirakawa Susumu

Abstract ID: 2088

To aid design decision concerning heavy impacts on heavyweight floors, it is necessary to be able to predict Fast-time weighted maximum sound pressure levels (Lp,Fmax) in the receiving room. For excitation directly on the heavyweight floor this can be carried out using Transient Statistical Energy Analysis (TSEA) in a predictive mode. However, the performance of floating floors is not always possible to accurately predict hence an inverse approach to TSEA, referred to as ITSEA, has been developed to determine the transient power. This paper compares the prediction of the Lp,Fmax using TSEA with normalized transient power input determined by ITSEA with measurements conducted in two test chambers with and without floor small floor toppings. For one-third octave bands, the maximum difference in Lp,Fmax between measurement and TSEA ranged from 5.3 to 8.3dB and 6 to 7dB when using W`in,ForcePlate and W`in,ITSEA respectively. For octave bands, the maximum difference in Lp,Fmax between measurement and TSEA ranged from 2.1 to 7.5dB and 2 to 7dB when using W`in,ForcePlate and W`in,ITSEA respectively

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Robust prediction metrics for structure-borne noise in timber buildings
Time: 11:40 am

Author: Ola Flodén

Abstract ID: 2111

This paper presents an investigation of prediction metrics for structure-borne noise in timber buildings, based on the vibration response of the structure. The purpose of the study is to derive a robust measure for predicting structure-borne noise in timber buildings based solely on the vibration response; a measure with a known correlation to the actual acoustic response. Such a measure is useful for establishing simplified numerical prediction models, and for making robust assessments of different design alternatives. The procedure has previously been applied to automotive applications with a valuable outcome for the industry. The vibration and sound pressure responses in a room of a multi-storey building are calculated using the finite element method. As excitation, a harmonic unit point load (20-300 Hz) located at another storey of the building is used. Based on the structural and acoustic response fields, scalar values are calculated by performing spatial and frequency domain averaging and summations. Various methods for calculating scalar values from the vibration response are investigated. The correlation between the vibration scalar values and the acoustic scalar values are presented.

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Thickness-resonance waves in underlays of floating screed
Time: 11:00 am

Author: Charlotte Crispin

Abstract ID: 2274

The prediction of the reduction of impact sound pressure level ?L according to annex C of the standard ISO 12354-2 gives an acceptable estimation of the floating floor’s performance for thin resilient layers.  However, the performance is often largely overestimated for thick resilient layers or for resilient layers combined with thermal layers. One reason for this is that the simplified model doesn’t account for the thickness resonances in the underlays which can greatly affect ?L. This is confirmed by comparing finite element and transfer matrix method simulations with experimental results. This paper establishes the mechanisms leading to the development of these resonance waves and provides some guidelines to estimate their negative effects on the ?L.

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Effect of ceiling and dry-type double floor on heavy-weight floor impact sound in concrete building and CLT building.
Time: 8:20 pm

Author: Takashi Yamauchi

Abstract ID: 2298

The air layer between the interior finishes and the structure is used as piping and wiring space. In many cases, ceilings and dry-type double floors are commonly constructed in Japan. However, the effect of the air layer of ceilings and dry-type double floors on the heavy-weight floor impact sound insulation performance has not yet quantitatively investigated. Therefore, in this study, the same floor and ceiling structures were constructed for concrete and CLT buildings, and the heavy-weight floor impact sound was investigated. As results, it was confirmed that the reduction amount of the heavy-weight floor impact sound by the ceiling tended to be smaller in CLT buildings than in concrete buildings. However, the trends were similar. Due to the dry-type double floor structure, the heavy-weight floor impact sound level was increased in concrete building and decreased in CLT building at 63 Hz in the octave band center frequency band. Therefore, it can be said that the dry-type double floor structure can be used to improve the heavy-weight floor impact sound performance in the CLT building.

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Effect of different types of ceilings on floor impact sound insulation performance in CLT model building
Time: 8:40 pm

Author: Atsuo HIRAMITSU

Abstract ID: 2693

The floor impact noise generated in a building often causes problems among residents. The floor impact sound insulation performance of timber construction buildings is lower than that of concrete construction. However, due to the large supply of wood and the stress-relieving effects of wood, the use of wood is being promoted around the world. In Japan, the Act on the Promotion of the Utilization of Wood in Public Buildings was enforced to promote the use of CLT (Cross Laminated Timber) for the effective use of wood. We have been experimentally investigating the effect of floor finish structure in CLT model building. In this paper, we report the measurement results of the change in floor impact sound insulation performance when the suspended ceiling structure was changed. As results, it was confirmed that the effect of the sound-absorbing material in the ceiling cavity and the effect of the double-layer ceiling board were effective. In addition, it was clarified that the dry-type double floor structure with rubber vibration insulator on its legs is an effective floor finish structure for improvement of heavy and light weight floor impact sound insulation performances.

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Prediction of one-third-octave band sound and vibration levels from heavy-hard impacts
Time: 2:40 pm

Author: Matthew Golden

Abstract ID: 2796

Noise and vibration due to dropping hard heavy weights is a common source of disturbance and complaint in residential, commercial, and mixed-use building types. The authors and others have worked on developing methodologies to accurately, repeatably, and conveniently measure heavy-hard impact noise and vibration in the field based on a standard weight drop. Separately, systems have been created to measure the force being injected into a building from heavy-hard impact. It has been shown that this force data can be used to successfully predict vibration levels in buildings if in-situ transfer functions are known. In this paper, the authors will present a novel one-third-octave band prediction method using the laboratory force data and a reference impact sheet to predict field performance without the need to measure transfer function. The method is evaluated using both noise and vibration measurements.

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Vibration transmission across fractured beam-to-column junctions of reinforced concrete
Time: 12:00 pm

Author: Marios Filippoupolitis

Abstract ID: 2840

To detect human survivors trapped in buildings after earthquakes by using structure-borne sound it is necessary to have knowledge of vibration transmission in collapsed and fragmented reinforced-concrete buildings. In this paper, Statistical Energy Analysis (SEA) is used to model the vibration transmission in seismic damaged reinforced concrete beam-to-column junctions where the connection between the beam and the column is made only via the steel reinforcement. An ensemble of 30 randomly damaged beam-to-column junctions was generated using a Monte Carlo simulation with FEM. Experimental SEA (ESEA) is then considered with two or three subsystems to determine the CLFs between the beam and the column with either bending modes or the combination of all mode types. It is shown that bending modes dominate the dynamic response and that the uncertainty of predicting the CLFs using FEM with ESEA is sufficiently low that it should be feasible to estimate the coupling even when the exact angle between the beam and the column is unknown. In addition, the use of two rather than three subsystems for the junction significantly decreases the number of negative coupling loss factors with ESEA.

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Subjective studies on impact sound in times of a pandemic — a comparison between a laboratory study and an online listening test
Time: 2:20 pm

Author: Markus Mueller-Trapet

Abstract ID: 2960

The National Research Council Canada is currently investigating the perceived annoyance due to impact sound in multi-unit residential buildings (MURBs). The first part of a subjective laboratory study on a number of different floor/ceiling assemblies was completed with 26 participants just before the start of the Covid-19 pandemic in 2020. To evaluate the feasibility of carrying out a similar study without in-person attendance, the same stimuli from the laboratory study were used to create an online listening test. The online listening test was created in JavaScript and HTML5 to run on any internet browser. This paper will present the results of the online listening test and compare them to the laboratory study, focusing on the obvious drawbacks of an uncontrolled remote study such as the uncertainty due to the participants’ headphones and listening environment. With an expectation that in-person studies will remain difficult to realize in the near future, this contribution provides evidence whether remote subjective listening tests are a viable alternative to controlled laboratory studies for impact sound.

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Apparent impact sound insulation performance of cross laminated timber floors with floating concrete toppings
Time: 7:40 pm

Author: Jianhui Zhou

Abstract ID: 3006

Mass timber buildings are gaining increasing popularity as a sustainable alternative to concrete and steel structures. Mass timber panels, especially cross-laminated timber (CLT), are often used as floors due to their dry and fast construction. CLT has poor impact sound insulation performance due to its lightweight and relatively high bending stiffness. Floating concrete toppings are often applied to increase both the airborne and impact sound insulation performance. However, the impact sound insulation performance of floating concrete toppings on CLT structural floors is affected by both the concrete thickness and resilient interlayer. This study investigated the efficiency of both continuous and discrete floating floor assemblies through mock-up building tests using small-scale concrete toppings according to ASTM E1007-16. It was found that the improvements by continuous floating floor assemblies are dependent on the concrete thicknesses and dynamic stiffness of resilient interlayers. The improvements cannot be well predicted by the equations developed for concrete structural floors. The highest apparent impact sound insulation class (AIIC) achieved with continuous floating floor assemblies in this study was 53 dBA, while that of the discrete floating floor assemblies was up to 62 dBA. The discrete floating floor solution showed great potential for use in mass timber buildings due to the high performance with thinner concrete toppings.

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