The development of sound absorbers made from PET fibres from recycled PET bottles presents a cheap and attractive solution for building retrofit applications. PET fibres of about 2-4 mm width are processed into a structure through random compaction and heat treatment, resulting in a sample that retains its shape. The normal incidence sound absorption coefficient of the samples was derived through measurements in an impedance tube, exhibiting potential effectiveness as a sound absorber. An innovative application of this material is the creation of transparent devices. This unique feature allows for sound attenuation without sacrificing natural light infiltration, addressing the common conflict between acoustic treatment and daylight access in architectural design. These items can serve as transparent partitions, sound absorbers, or design gadgets for lighting in areas near windows. Furthermore, using recycled PET fibres not only contributes to waste reduction but also promotes sustainability in construction, aligning the research’s aim with contemporary environmental goals. By offering functional aesthetic solutions that enhance both acoustic comfort and visual appeal, these PET fibre-based sound absorbers hold potential for improving the habitability of retrofitted spaces.