The scientific article Sound Absorption of Tufted Carpets Produced from Coarse Wool of Mountain Sheep has been published in Journal of Natural Fibers. The article is co-authored by Jan Broda, Katarzyna Kobiela-Mendrek, Marcin Bączek, Monika Rom and Ingvild Espelien, and is an important contribution to the study of wool’s properties.
As part of the ongoing research in the WOOLUME project, looking at good utilization of coarse Polish mountain wool, is an important exploration. Tufting is a technique with cut and loop piles and to which degree this technique used on coarse wool can contribute to sound absorbing properties is interesting to study.
Some tufting history
Wool from Polish mountain sheep is coarse, highly differentiated both in thickness and length and contains a significant content of medullated fibers and kemp. Despite its poor characteristics, the wool can be used for the production of rag yarns fit for pile carpets with tufting technique. The carpets possess acceptable sound absorbing capacity comparable to other similar products obtained from other wool types, which is dependent on both pile types and their parameters.
The hand tufting technique was invented at the end of the nineteenth century in Dalton (Georgia, USA) where it was first applied for handicraft production of bedspreads, mats, and bathrobes. The technique involves stitching the yarn into the backing fabric to create a loop, cut, or mixed piles. Loop piles are formed when the yarn inserted is caught by loopers and pulled through the backing to a set length. Cut piles are formed by cutting the piles at their maximum length, with blades operating in tandem with the loopers. In the 1930s, a modified single-needle commercial sewing machine was adopted for tufting. The machine enabled tufting of thick yarn into muslin without tearing the fabric and was coupled with a knife to cut the loops.
In the next few years, tufting machines with four, then eight, twenty-four, or more needles enabling the formation of parallel rows were constructed. Machines were introduced to the industrial practice, which soon resulted in the rapid growth of the mechanized tufting industry. After the second world war, in the 1950s, tufting machines were getting more and more common and were equipped with several hundred needles to stitch hundreds of pile yarn rows. In the next years, tufting dominated carpet manufacturing. It is estimated that nowadays, tufting is a common technique widely used for the production of 90% of the carpets available in the market. The introduction of the tufting technique on a large scale coincided with the development of new synthetic fibers. Application of these fibers significantly accelerated the growth of carpet production. The new yarns, continuous filament nylon yarns in particular, provided good quality and high durability of carpets at a relatively low price, out-performing wool as the raw-material with a much cheaper price point.
Wool carpets used as floor coverings and interior decorations offer additional considerable advantages in terms of thermal insulation and heat balance in buildings. Moreover, such carpets are highly effective in controlling indoor noise and reducing the reverberation of sound. Carpets are some of the most versatile sound-absorbing materials which absorb both airwave sounds and reduce surface noise generation. Additionally, carpets reduce the impact of sound transmission between stories in multi-storied buildings.
In our previous studies, the acoustic performance of felt and fabrics manufactured from Polish mountain sheep wool was analyzed. The investigations showed that the wool of mountain sheep, which is often disregarded and treated as a waste product of sheep husbandry, is a valuable raw material that can be used to produce carpets and panels with good sound-absorbing properties. The paper presents the results of further studies on the utilization of coarse wool obtained from mountain sheep to produce rag yarns suitable for the production of pile carpets with the tufting technique. During this investigation, the raw wool and yarns were characterized in detail, and the possibility of using yarns in the tufting technique was explored. Then, the sound absorption capacity and transmission loss of the obtained materials in relation to the type of piles, pile height, and density were analyzed.
Conclusion: Apart from their decorative function, carpets produced from Polish mountain sheep wool with the tufting technique can serve as valuable sound absorbing material to lessen noise, reduce reverberation, and improve the acoustic comfort of the room.
Access to the full article is provided in this link.
This research was funded by the Norway Grant titled “Polish sheep wool for improved resource utilisation and value creation.” NOR/POLNOR/WOOLUME/0007/2019