| 1. |
- Autio, Hanna, et al.
(author)
-
An Iterative Ray Tracing Algorithm to Increase Simulation Speed While Maintaining Overall Precision
- 2023
-
In: Acoustics. - : MDPI AG. - 2624-599X. ; 5:1, s. 320-342
-
Journal article (peer-reviewed)abstract
- Ray tracing is a frequently used method for acoustic simulations, valued for its calculation speed and ease of use. Although it is fast, there are no fully ray tracing-based real-time simulation methods or engines. Under real-time restrictions, ray tracing simulations lose precision and the variance inherent in the random simulation method has too much impact on the outcome. In this paper, an algorithm called iterative ray tracing is presented that reduces the negative effects of real-time restrictions by iteratively improving the initial calculation and increasing the precision over time. In addition, new estimates of the expected value and variance of ray tracing simulations are presented and used to show the iteration steps in the new algorithm reduce variance, while maintaining the expected value. Simulations using iterative ray tracing are compared to measurements and simulations using the classical ray tracing method, and it is shown that iterative ray tracing can be used to improve precision over time. Although more testing is needed, iterative ray tracing can be used to extend most ray tracing algorithms, in order to decrease the adverse effects of real-time restrictions.
|
|
| 2. |
- Autio, Hanna, et al.
(author)
-
The influence of different scattering algorithms on room acoustic simulations in rectangular rooms
- 2021
-
In: Buildings. - : MDPI AG. - 2075-5309. ; 11:9
-
Journal article (peer-reviewed)abstract
- Raytracing is a widespread tool for room acoustic simulations, and one of its main advan-tages is the inclusion of surface scattering. Although surface scattering has been acknowledged as a central aspect of accurate raytracing simulations for many years, there is ongoing research into its effects and how to implement it better. This study evaluates three different algorithms for surface scattering in raytracers, referred to as on–off scattering, perturbation scattering, and diffuse field scattering. Their theoretical foundation is discussed, and the physical accuracy of the resulting simulations is evaluated by comparing simulated room acoustic parameters to measurements. It is found that the choice of surface scattering algorithm has a significant impact on the simulation outcomes, both in terms of physical accuracy and in terms of usability. Additionally, there are differences in the parametrization of surface scattering depending on the algorithm chosen. Of the three tested algorithms, the most commonly used algorithm (on–off scattering) seems to have the best properties for simulations.
|
|
| 3. |
- Bader Eddin, Mohamad, et al.
(author)
-
Prediction of Sound Insulation Using Artificial Neural Networks—Part II : Lightweight Wooden Façade Structures
- 2022
-
In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:14
-
Journal article (peer-reviewed)abstract
- A prediction model based on artificial neural networks is adapted to forecast the acoustic performance of airborne sound insulation of various lightweight wooden façade walls. A total of 100 insulation curves were used to develop the prediction model. The data are laboratory measurements of façade walls in one-third-octave bands (50 Hz–5 kHz). For each façade wall, geometric and physical information (material type, dimensions, thicknesses, densities, and more) are used as input parameters. The model shows a satisfactory predictive capability for airborne sound reduction. A higher accuracy is obtained at middle frequencies (250 Hz–1 kHz), while lower and higher frequency ranges often show higher deviations. The weighted airborne sound reduction index ((Formula presented.)) of façades can be estimated with a maximum difference of 3 dB. Sometimes, the model shows high variations within fundamental and critical frequencies that influence the predictive precision. A sensitivity analysis is implemented to investigate the significance of parameters in insulation estimations. The material density (i.e., cross-laminated timber panel, gypsum board), thickness of the insulation materials, thickness and spacing between interior studs and the total density of façades are factors of significant weight on predictions. The results also emphasize the importance of façade thickness and the total density of the clustered exterior layers.
|
|
| 4. |
- Eddin, Mohamad Bader, et al.
(author)
-
Prediction of Sound Insulation Using Artificial Neural Networks—Part I : LightweightWooden Floor Structures
- 2022
-
In: Acoustics. - : MDPI AG. - 2624-599X. ; 4:1, s. 203-226
-
Journal article (peer-reviewed)abstract
- The artificial neural networks approach is applied to estimate the acoustic performance for airborne and impact sound insulation curves of different lightweight wooden floors. The prediction model is developed based on 252 standardized laboratory measurement curves in one-third octave bands (50-5000 Hz). Physical and geometric characteristics of each floor structure (materials, thickness, density, dimensions, mass and more) are utilized as network parameters. The predictive capability is satisfactory, and the model can estimate airborne sound better than impact sound cases especially in the middle-frequency range (250-1000 Hz), while higher frequency bands often show high errors. The forecast of the weighted airborne sound reduction index Rw was calculated with a maximum error of 2 dB. However, the error increased up to 5 dB in the worse case prediction of the weighted normalized impact sound pressure level Ln,w. The model showed high variations near the fundamental and critical frequency areas which affect the accuracy. A feature attribution analysis explored the essential parameters on estimation of sound insulation. The thickness of the insulation materials, the density of cross-laminated timber slab and the concrete floating floors and the total density of floor structures seem to affect predictions the most. A comparison between wet and dry floor solution systems indicated the importance of the upper part of floors to estimate airborne and impact sound in low frequencies.
|
|
| 5. |
- Eddin, Mohamad Bader, et al.
(author)
-
Sound insulation of lightweight wooden floor structures : ANN model and sensitivity analysis
- 2022
-
In: Internoise 2022 - 51st International Congress and Exposition on Noise Control Engineering. - 9781906913427
-
Conference paper (peer-reviewed)abstract
- The study aims to develop an artificial neural networks (ANN) model to estimate the acoustic performance for airborne and impact sound insulation curves of different lightweight wooden floors. The prediction model is developed using 252 standardized laboratory measurement curves in one-third octave bands (50 − 5000 Hz). Each floor structure has been divided into three parts in the database: upper, main and ceiling parts. Physical and geometric characteristics (materials, thickness, density, dimensions, mass, and more) are used as network parameters. The results demonstrated that the predictive ability of the model is satisfactory. The forecast of the weighted airborne sound reduction index Rw was calculated with a maximum error of 2 dB. However, it is increased up to 5 dB in the worst case prediction of the weighted normalized impact sound pressure level Ln,w. A sensitivity analysis explored the essential parameters on sound insulation estimation. The thickness and the density of upper and main parts of the floors seem to affect estimations the most in all frequencies. In addition, no remarkable attribution has been found for the thickness and density of the ceiling part of the structures.
|
|
| 6. |
- Nilsson, Erik, et al.
(author)
-
Acoustical Treatments on Ventilation Ducts through Walls : Experimental Results and Novel Models
- 2022
-
In: Acoustics. - : MDPI AG. - 2624-599X. ; 4:1, s. 276-296
-
Journal article (peer-reviewed)abstract
- Sound reduction is complex to estimate for acoustical treatments on ventilation ducts through walls. Various acoustical treatments are available for ventilation ducts, including internal lining (absorption along the inner perimeter), external lagging (external sound insulation), silencer, and suspended ceilings. Previous studies have examined how silencers and the internal lining affect the sound transmission of ventilation ducts. However, there are few theories to predict the effect of external lagging in combination with ventilation ducts and how the total sound reduction is affected. This article aims to investigate different acoustical treatments and develop theoretical models when external lagging with stone wool is used to reduce flanking sound transmission via the surface area of ventilation ducts. Theoretical models are developed for external lagging and compared with measurement data. Measurements and theory are generally in good agreement over the third-octave band range of 100–5000 Hz. The developed models clarify that the distance closest to the wall has the main impact on sound reduction for a combined system with a wall and a ventilation duct. Suspended ceilings and silencers are found to be enough as acoustical treatments for certain combinations of ventilation ducts and walls. However, external lagging seems to be the only effective solution in offices and schools when a large ventilation duct passes through a wall with high sound reduction.
|
|
| 7. |
- Nilsson, Erik, et al.
(author)
-
Sound Reduction of Ventilation Ducts through Walls : Experimental Results and Updated Models
- 2021
-
In: Acoustics. - : MDPI AG. - 2624-599X. ; 3:4, s. 695-716
-
Journal article (peer-reviewed)abstract
- Ventilation ducts can have a negative effect on the sound reduction index between two rooms if they pass through the dividing structure without treatments. The overall sound reduction of a ventilation duct is dependent on several factors including the transmission loss when sound is breaking in and out from the duct. This study aims to model the sound reduction of a combined system with a separating wall and a ventilation duct through it. Three walls, characterized according to ISO 717-1, are combined with three different ventilation ducts, two circular and one rectangular with different dimensions. Laboratory measurement data are used to determine the sound reduction of the different configurations and the type of treatments needed for each configuration. A proposed model with existing theory for describing sound transmission losses of circular and rectangular ventilation ducts predicts the shape of the measurement data for many frequency bands. A new theory part is developed through an iterative process for circular ducts, which is based on measurements with previous methods and studies as a guide because the existing prediction scheme is somewhat perplexing. For rectangular ducts, the existing theory has been updated to better match measurement data. The application of the proposed theory and model in this article shows similar results when compared to measurements. The difference in weighted sound reduction index between developed theories and measurement data is 0–1 dB for every configuration.
|
|
| 8. |
- Vardaxis, Nikolaos Georgios, et al.
(author)
-
Acoustic comfort assessment in heavyweight residential buildings : Acoustic data associated to subjective responses
- 2019
-
In: Proceedings of the 23rd International Congress on Acoustics : Integrating 4th EAA Euroregio 2019 - Integrating 4th EAA Euroregio 2019. - 2226-7808 .- 2415-1599. - 9783939296157 ; 2019-September, s. 836-843
-
Conference paper (peer-reviewed)abstract
- This article presents a study aiming to explore and evaluate acoustic comfort in residential multistory buildings in Sweden. Acoustic data was associated to self-reported responses acquired by a survey: a questionnaire was setup researching the response to noise annoyance from multiple sources in a flat and the emotional reactions of tenants to the acoustic climate at home. An assessment of acoustic comfort in the test apartments was performed utilizing the circumplex model of affect. A sample of 353 residents offered their ratings on 12 bipolar scales regarding their feelings towards their living sound environment. Two dimensions were identified: pleasantness and activation. Statistical models were developed using acoustic and structural variables. L'#$,&,'((predicted best pleasantness and number of flats per building predicted best activation. A new acoustic comfort indicator is suggested based on the pleasantness model and four novel acoustic comfort classes are proposed as: AC-1: Very good, AC-2: Good, AC-3: Acceptable, AC-4: No comfort.
|
|
| 9. |
- Vardaxis, Nikolaos Georgios, et al.
(author)
-
Evaluating Laboratory Measurements for Sound Insulation of Cross-Laminated Timber (CLT) Floors : Configurations in Lightweight Buildings
- 2022
-
In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:15
-
Journal article (peer-reviewed)abstract
- Cross-laminated timber (CLT) floors with supplementary layers or floating floors comprise a common solution in new multistory timber structures. However, bare CLT components provide poor sound insulation, especially in low frequencies during structure-borne sound propagation. Thus, floor configurations in wooden buildings deploy more layers for improved acoustic behavior. Twelve contemporary CLT floors were analyzed after laboratory measurements of airborne sound reduction and impact sound transmission utilizing the following indicators: (Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.), and (Formula presented.) (per ISO 10140, ISO 717). An increase in sound insulation was achieved thanks to added total mass and thickness, testing layers of the following: elastic mat for vibration isolation, wool insulation, gypsum boards, plywood, concrete screed, and wooden parquet floor. The results indicate that multilayered CLT floors can provide improvements of up to 22 dB for airborne sound and 32 dB for impact sound indicators compared with the bare CLT slab. Floating floor configurations with dry floor solutions (concrete screed) and wooden parquet floors stand out as the optimal cases. The parquet floor provides a 1–2 dB improvement only for impact sound indicators in floating floor setups (or higher in three cases).
|
|
| 10. |
- Vardaxis, Nikolaos Georgios, et al.
(author)
-
Finite Element Modeling for vibration transmission in a Cross Laminated Timber structure
- 2016
-
In: WCTE 2016 - World Conference on Timber Engineering. - 9783903039001
-
Conference paper (peer-reviewed)abstract
- This paper deals with a certain type of C.L.T. (Cross Laminated Timber) construction, in a residential building in Fristad, Sweden. The objective is to study impact noise transmission, at the lower frequency range (10-200 Hz), where wooden dwellings perform inefficiently, in terms of acoustic quality. The vibrational behavior of lightweight structures and specifically a multilayered floor separating two vertically adjacent bedrooms are investigated. A numerical model of the multilayered test plate, which includes sound insulation and vibration isolation layers, is developed using the Finite Element Method (F.E.M.) in commercial software. The design process, the analysis and improvement of the calculated outcome concerning accuracy and complexity are of interest. In situ vibration measurements were also performed so as to evaluate the structures dynamic behavior in reality and consequently the validity of the modelled results. The whole process from design to evaluation is discussed thoroughly, where uncertainties of the complex F.E.M. model and the approximations of the real structure are analyzed. Numerical comparisons are presented including mechanical mobility and impact noise transmission results. The overall aim is to set up a template of calculations that can be used as a prediction tool in the future by the industry and researchers.
|
|
