Towards more reliable measurements of sound absorption coefficient in reverberation rooms: An Inter-Laboratory Test

Scrosati, Chiara; Martellotta, Francesco; Pompoli, Francesco; Schiavi, Alessandro; Prato, Andrea; D’Orazio, Dario; Garai, Massimo; Granzotto, Nicola; Bella, Antonino Di; Scamoni, Fabio; Depalma, Michele; Marescotti, Cristina; Serpilli, Fabio; Lori, Valter; Nataletti, Pietro; Annesi, Diego; Moschetto, Antonio; Baruffa, R.; Napoli, G. De; D'Angelo, Filippo; Filippo, Sabato Di

doi:10.1016/j.apacoust.2020.107298

Cited by 23 publications

(21 citation statements)

References 18 publications

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“…The 20 mm thick panel feature an absorption peak between 2500 Hz and 4000 Hz, achieving a value of 1.20; the peak is broader than those featured by 20 mm thick panels of types A-C. Values higher than 1 may occur in the measurements with finite sample size for materials with high absorption properties [39,40]. The 20 mm sample of panel D achieves significant absorption (>0.40) above 1000 Hz, while for panels A-C, this occurred above 2500 Hz, 2000 Hz, and 3150 Hz, respectively.…”

Section: Effect Of Sample Thickness and Concrete Typementioning

confidence: 96%

More Than Just Concrete: Acoustically Efficient Porous Concrete with Different Aggregate Shape and Gradation

et al. 2021

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The interest in the use of resistant acoustic materials has put further attention on the use of porous concrete in the building industry. This work investigates the acoustic properties of four different mix designs of porous concrete obtained with two types of aggregates, that is, normal weight and lightweight aggregates. The assessment of the sound-absorbing performances has been conducted in the small-scale reverberation room (SSRR) at Politecnico di Torino (Italy), in agreement with the procedure indicated in the ISO 354 Standard. For each concrete type, three panel thicknesses, i.e., 20 mm, 40 mm, and 60 mm, were tested. Moreover, different mounting conditions were investigated, considering the combination of single panels in multiple layers, adding an air gap between the panel and the backing, and inserting a layer of rock wool in the air gap itself. The results show weighted absorption coefficients (αw) in the range of 0.30 to 0.75 depending on the thickness and mounting conditions. These encouraging values make these materials useful for efficient practical applications in indoor and outdoor environments.

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Section: Effect Of Sample Thickness and Concrete Typementioning

confidence: 96%

More Than Just Concrete: Acoustically Efficient Porous Concrete with Different Aggregate Shape and Gradation

et al. 2021

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“…Secondly, the reverberation time is measured to determine in the room the sound absorption corrections necessary for various acoustic measurements, such as the sound insulation measurement according to ISO 140 (all parts) and the sound power of noise sources according to ISO 3740 [54]. Uncertainties due to reproducibility concerns are crucial for the reverberation room method [59].…”

Section: Measuring In a Reverberation Roommentioning

confidence: 99%

Sound-Absorbing Acoustic Concretes: A Review

et al. 2021

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Noise is continuously treated as an annoyance to humans and indeed commotion contamination shows up within the environment, causing inconvenience. This is likewise interesting to the engineering tactic that inclines to develop this noise proliferation. The basics of the sound-retaining proliferation, sound-absorbing properties, and its variables were rarely considered by previous researchers. Thus, the acoustic performance and sound insulation of constructions have gained significance over the last five decades due to the trend for accommodating inner-city flat and multi-story residential building condominiums. Due to this dilemma, the proliferation of high-driven entertaining schemes has engaged extraordinary demands on building for its acoustic performance. Yet, construction industries worldwide have started to mainly use sound-absorbing concrete to reduce the frequency of sounds in opened-and-closed areas and increase sound insulation. As reported, the concrete acoustic properties generally rely on its density, exhibiting that the lighter ones, such as cellular concrete, will absorb more sound than high-density concretes. However, this paper has an objective to afford a wide-ranging review of sound-absorbing acoustic concretes, including the measurement techniques and insulation characteristics of building materials and the sound absorption properties of construction materials. It is also intended to extensively review to provide insights into the possible use of a typical sound-absorbing acoustic concrete in today’s building industry to enhance housing occupants’ efficiency, comfort, well-being, and safety.

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“…In a practical condition, a mixing room with small absorption and the greatest scattering room surfaces are desired [3,4]. Although specific guidelines for qualification of reverberation chambers are provided by the standards, previous studies pointed out poor repeatability and reproducibility of measured acoustic quantities in different laboratories even though they meet the criteria in the standards [5,6]. The inaccurate measurement of the acoustic properties poses a huge challenge for acoustic engineers and manufacturers to compare the acoustical performance of building elements measured across acoustic laboratories.…”

Section: Introductionmentioning

confidence: 99%

“…Second, paralleled walls or a lack of scattering elements make it difficult for an ideal diffuse condition [8]. Finally, the 'suction' effect of the absorbing sample causes an anisotropic energy distribution in the chamber [6].…”

Section: Introductionmentioning

confidence: 99%

“…Other indirect methods, such as the number of peaks [23] and the mixing time [24], were also proposed to quantify the diffuseness of the sound field by analyzing the details of the impulse response. Scrosati et al [6] quantified the diffuseness of multiple reverberation chambers by using a reference absorber method, and the authors found that the use of a reference absorber might be valid but challenging because the true value of the reference absorber is still in doubt.…”

Section: Introductionmentioning

confidence: 99%

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Diffuseness Quantification in a Reverberation Chamber and Its Variation with Fine-Resolution Measurements

Zhang

Lee

2021

Buildings

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Insufficient diffuseness is the major cause of the poor repeatability and reproducibility of building acoustical measurements in a reverberation chamber. Inaccurate results were reported for the prevailing methods in ISO and ASTM standards. Many previous studies, thus, have proposed new methods to quantify the diffuseness of a reverberation chamber more accurately, but there is no general agreement among researchers on the most reliable method. The number of measurement samples required for these diffuseness metrics is also unclear, even though it significantly impacts the robustness of the methods. This study, therefore, aims to compare the performance of the two widely used diffuseness metrics (spatial variation of sound pressure levels and the relative standard deviation of decay rates) in the standards and the recently introduced metric (degree of time series fluctuation). The measurements were carried out with fine resolution microphone positions and varied configurations of acoustic diffusers. The degree of time series fluctuation showed the best correlation with varying diffuser configurations in the low-frequency range. Confidence intervals and coefficients of variation of the three metrics by random sampling also indicated that DTF is more reliable for evaluating the diffuseness in a sound field as it is less influenced by the number of sampling.

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Towards more reliable measurements of sound absorption coefficient in reverberation rooms: An Inter-Laboratory Test

Cited by 23 publications

References 18 publications

More Than Just Concrete: Acoustically Efficient Porous Concrete with Different Aggregate Shape and Gradation

More Than Just Concrete: Acoustically Efficient Porous Concrete with Different Aggregate Shape and Gradation

Sound-Absorbing Acoustic Concretes: A Review

Diffuseness Quantification in a Reverberation Chamber and Its Variation with Fine-Resolution Measurements

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