In the last 40 to 50 years, the use and variety of available specialized
sound-absorbing materials has increased greatly. This has
been due mainly to both improve technology and public concern
about noise in everyday life. Architects and acoustical engineers
now have a wide choice of sound-absorbing materials that not
only provide the desired acoustical properties, but also offer an
extremely wide variety of colors, shapes, sizes, light reflectivity,
fire ratings, and methods of attachment – to say nothing of the costs
of purchase, installation, upkeep, etc.8