How small-scale variation in mineral wool products effect random incidence sound absorption

Mineral wool products are produced by creating a spray of fibres, that is collected and made into slabs. This randomized spray can lead to small variations across a slab. Nevertheless, mineral wool slabs are often treated in acoustics as locally reacting perfectly homogeneous, isotropic materials. This means that small-scale characterisations are extrapolated to large-scale without considering the impact from possible variations in a large-scale setup. The question is how the small-scale characterisations should be used for large-scale setups with this in mind. Three products with the same thickness and density, but with significantly different specific airflow resistances were selected for random incidence sound absorption tests. The products were all specially made ceiling tiles and measurements were conducted in E200 setup according to ISO 354:2003. The tiles were gradually exchanged in a random fashion, so measurement results were obtained using a combination of tiles with different specific airflow resistances. Results showed a surprisingly linear relation between the sound absorption and the average specific airflow resistance of tiles used in the measurements. The results point to that variations in products must be observed, but also that small variations in specific airflow resistance in standardized products are insignificant.

Indirect determination of airflow resistance of textiles with reference samples

Airflow resistance is a non-acoustic parameter of great relevance in the acoustic characterization of porous materials. It is used in several sound absorbing material prediction models and it is also a control parameter for acoustic conditioning and insulation in different building solutions. The ISO 9053 standard defines several methods to obtain it, using both direct measurements and indirect techniques. However, both procedures may involve problems related to the placement of the textile samples in the tube or to the stability of the samples during testing. In this work, the use of reference materials to stabilize the measurement of thin materials is proposed. Airflow resistance results obtained for different materials in an impedance tube are presented. The tests have been carried out by following the Ingard & Dear method, as an indirect technique accepted by the standard. Several material compositions with a wide range of airflow resistance values have been analyzed with different reference materials.

Voice Rehabilitation by Voice Prostheses After Total Laryngectomy: A Systematic Review and Network Meta-Analysis for 11,918 Patients

Purpose Our aim was to assess the different voice prostheses (VPs) to identify the most efficient, safest, patient-tailored, longest lifetime, and inexpensive VPs and assess the different factors affecting their quality. Method In September 2017, 15 databases were searched to include all randomized controlled trials. A new search was done in May 2019 to include all other study design articles, which include all the new-era VPs subtypes. Network meta-analysis (NMA) was applied to all 27 outcomes, besides NMA overall and partial order setting was done by using Hasse scatter plots. p values were used in NMA, where the best VPs are approaching one and the least approaches zero. Meta-analysis was done for the rest of the outcomes. Results Two hundred one articles were eligible for inclusion in our study ( N = 11,918). Provox-2 was significantly the most efficient and safest device concerning the most patient preference (odds ratio [ OR ] = 33.88 [0.65, 1762.24]; p = .92), the least dislodgement (risk ratio [RR] = 0.27 [0.13, 0.57]; p = .79), the least airflow resistance (RR = 0.42 [0.08, 2.11]; p = .84), the least granulation formation (RR = 0.73 [0.02, 26.32]; p = .60), and the least VPs' inaccurate size (RR = 0.77 (0.23, 2.61); p = .66). Heat and moisture exchanger addition showed a significant increase in maximum phonation time and breathing experience, with p values (1 and .59), respectively. While heat and moisture exchanger addition showed a significant decline in stoma cleaning frequency, coughing frequency, forced expectoration, sputum production, sleeping problems, and loosening of adhesive, with p values (.99, .72, .69, .96, 1, and 0.96), respectively, Groningen low resistance and Nijdam were considered the worst devices with both overall mean p value of .44. Conclusions Provox-2 is considered the best choice as being the most preferable for patients, with the least airflow resistance, dislodgment, granulation formation, and prosthesis inaccurate size. Groningen low resistance and Nijdam were considered the worst devices according to our analysis. Supplemental Material https://doi.org/10.23641/asha.14802903

Preliminary Evaluation of Filtration Efficiency and Differential Pressure ASTM F3502 Testing Methods of Non-Medical Masks Using a Face Filtration Mount

Research surrounding the mandated use of non-medical fabric masks is inconsistent and often confusing when compared to the standard N95. A recently published standard from ASTM International and the Centers for Disease Control and Prevention attempts to normalize evaluation procedures. The purpose of this study is to conduct a preliminary evaluation of the new methods for testing filtration efficiency of masks outlined by ASTM International F3502, where results can be directly compared to standards outlined for non-medical fabric masks. Eleven consumer non-medical fabric masks were tested for filtration efficiency and airflow resistance using a face filtration mount in accordance with the newly released ASTM International standard for facial barriers. The mean FE% (SD) ranged from 0.46% (0.44) to 11.80% (2.76) with the 3-layer athletic mesh having the highest performance and the highest deviations. All the masks tested following the procedure failed to meet to minimum FE of 20%; however all masks performed below the minimum upper limits for airflow resistance. Using a non-medical fabric masks as the sole mitigation strategy may not be as effective, as previously reported. With efforts to standardize and regulate the non-medical fabric mask market, this study demonstrates a variety of currently available consumer mask products do not meet the minimum standards nor are these remotely close to the standards of surgical or N95 masks.

Louvred Noise Barrier for Traffic Noise Reduction

Environmental issues near roads become more and more important in our society daily life. One of the most critical environmental issues is traffic noise. The present paper study louvred noise barrier designed by authors. The louvred noise barrier provides sound attenuation while allowing airflow and sunlight through it. Since the airflow resistance of the barrier is low, it requires a shallow foundation compared to conventional noise barriers. The sound attenuation performance of the louvred noise barrier was tested experimentally in a sound transmission chamber. Airflow resistance simulated using a computational fluid dynamics model. The simulation and experimental study were done with different louvred noise barrier setup: change of louvre blade angle and sound-absorbing material thickness. The results showed potential for future development for the field testing. Sound attenuation was highest in 2500 Hz and 3150 Hz octave frequency bands. Depending on the louvred barrier setup, sound attenuation was up to 28 dB(A) in mentioned frequency bands. The equivalent sound pressure level reduced up to 17 dB(A). The results showed that an increase in the louvre blade angle increases sound attenuation and increases airflow resistance.