Speaker
Description
Sound pollution has long been known to inflict problems to both humans and animals. Judging sound to be pollution does depend on situation. Typical protections come in many forms according to specific problem. Sound absorber is one of those forms playing an important role in reducing reverberating effect in rooms or auditoriums. General commercial absorbers are constructed from mineral wool or asbestos That are harmful to respiration system. Therefore, natural materials become of interest. In this work, we use an impedance tube to determine the sound absorption coefficient of natural materials—rice straw, pine leaves, and grey sedge. The specimens are dried and mixed to certain ratios forming 6-cm diameter disk panels with the thickness of 1.5 cm using powder glue as binder. The measurement is based on ISO 10534-2 standard and covers the frequency range of 400-2500 Hz with backspacing of 0, 10, 20, 30 mm. It is found that the sound absorption coefficient of dried grey sedge shows the strongest absorption of ~0.99 at 500 Hz with the backspacing of 30 mm while that without smacking also display strong absorption, 0.8, at 1500 Hz. For the absorption of dried rice straw, the results indicate that without space behind the sample the absorption is strongest, ~0.96, at 2258 Hz while other spacings provide the value of ~0.85 for lower frequencies. Finally, the pine-leaf panel yields weakest absorption of no more than 0.8 comparing to those of other materials. We can see that these natural materials if properly prepared can perform as sound absorbers.
