Acoustic Performance of Sound Absorbing Materials Produced from Wool of Local Mountain Sheep

Abstract

Wool of mountain sheep, treated nowadays as a waste or troublesome byproduct of sheep husbandry, was used for the production of sound-absorbing materials. Felts of two different thicknesses were produced from loose fibres. Additionally, two types of yarn, ring spun and core rug, were obtained. The yarns were used for the production of tufted fabric with cut and loop piles. During the examinations, basic parameters of the obtained materials were determined. Then, according to standard procedure with the use of impedance tube, the sound absorption coefficient was measured, and the noise reduction coefficient (NRC) was calculated. It was revealed that felt produced from coarse wool exhibits high porosity, and its sound absorbing capacity is strongly related to the felt thickness. For thicker felt the NRC achieved 0.4, which is comparable with the NRC of commercial ceiling tiles. It was shown that the crucial parameter influencing the sound absorption of the tufted fabrics was the pile height. For both types of yarns, when the height of the pile was increased from 12 to 16 mm, the NRC increased from 0.4 to 0.42. The manufactured materials made from local wool possess good absorption capacity, similar to commercial products usually made from more expensive wool types. The materials look nice and can be used for noise reduction as inner acoustic screens, panels, or carpets.

Eco-Friendly Processing of Wool and Sustainable Valorization of This Natural Bioresource

“…According to Broda and coworkers [192], the coarse wool carpets produced by the tufted technique seem to be very good sound absorbents. The works of Kobiela-Mendrek and coworkers support the same assumption [193].…”

Application of Scirpus grossus fiber as a sound absorber

“…The maximum SAC value of 0.56 exhibited best sound absorption at 2000 Hz for specimen of SG with its thickness of 10 mm coated with PAS of 1.0-mm diameter is similar to that for specimen of SG with its thickness of 20 mm coated with PAS of 1.5-mm diameter. This could be due to the sound waves absorbed by a low density of SG loosely packed together with a plenty of space transferred through a larger size of PAS hole is approximately similar to that absorbed by a high density of SG densely packed together with a limited space transferred through a narrow PAS hole size [ 2 ]. A difference in the SAC value of SG specimen coated PAS with the hole diameters each of 1.0, 1.5 and 2.5 mm at 2000 Hz could be more significant compared to that at the sound frequency of 125 Hz.…”

“…The application of the natural materials attracted significant interest for more than a century could be due to the physical properties of natural plant fibers offer opportunity of sound absorbers potentially used in acoustic engineering to reduce noise pollution [ 1 ]. The manufacturing of natural materials possessed good absorption capacity could be similar to the commercial products usually made of the expensive synthetic materials used for the reduction of noise [ 2 ]. Noise pollution associated with several negative effects on both land and in the sea can cause health problems for people and wildlife, contributing to the cause of heart attacks affected an annoyance and sleep disturbance [ [3] , [4] , [5] ].…”

Mechanical and radar absorption properties of sheep wool/epoxy composites

“…High sound absorption capacity and extraordinary acoustic properties of wool felt have been long known and are commercially used in piano manufacturing. Kobiela-Mendrek et al were studied acoustic performance of sound absorbing properties of sheep wool materials produced by felting and tufting techniques (Broda et al , 2022). They concluded that acoustic properties of the produced materials depend on their structure and parameters.…”