In simple terms, noise is unwanted sound. A sound is a form of energy that is emitted by a vibrating body and on reaching the ear causes the sensation of hearing through nerves. Sounds produced by all vibrating bodies are not audible. The frequency limits of audibility are from 20 HZ 10 20,000 HZ. Excessive levels of sound can cause permanent hearing loss while continuous exposure could be physiologically and psychologically deleterious to one’s well-being.
Change with changing trends.
Nowadays much importance is given to the acoustical environment. Noise control and its principles play an important role in creating an acoustically pleasing environment and providing vibrational healing. This can be achieved when the intensity of sound is brought down to a level that is not harmful to human cars. Achieving a pleasing environment can be obtained by using various techniques that employ different materials. One such technique is by absorbing the sound. This paper review and describes how the physical prosperities of materials like fibre size, material thickness, density, porosity, and tortuosity can change the absorption behaviour. The sound absorption of different natural fibres was experimentally tested.
The results show the relationship between natural fibres like kenaf, bamboo, paddy and the sound absorption, material density, thickness, and air gap. Higher airflow resistance always gives better sound absorption values but for airflow resistance higher than 1000 the sound absorption hasfewer values because ofdifficult movements of a sound wave through the materials. More fibres can create a more tortuous path (increase tortuosity) and can also increase the flow resistivity.