Optimization of the Noise Control Process of a Polystyrene Silencer and Assessment of Its Role in Sound Insertion Loss Index Variation as Enclosure in a Laboratory

Exposure to excessive sound is considered as one of the health problems of workers all over the world. One of the most important ways to control sound is using absorbent material around the sound source in the form of a silencer. This study intended to determine the sound insertion loss of a polystyrene silencer and its structural changes in order to improve sound reduction.
The silencer was built as an enclosure using polystyrene foam in the form of a rectangle (with no floor) with a density of 20 kg/m3, thickness of 5 cm, and the size of 1 × 1 × 1.5 m. Moreover, the sound level of 100 dB was generated by a speaker, perpendicular to the ground, as the sound source and two microphones were used to collect sound. Then, sound reduction values were examined by changes such as increasing thickness and creating a hole on the walls.
Findings: According to the results, through the polystyrene silencer with a thickness of 5 cm and without a hole, the maximum sound reduction of 34.5 dB at 500 Hz frequency was achieved. Furthermore, increasing the thickness to 7 cm and adding a hole with a diameter of 2 cm caused higher sound reduction than the silencer without changes in frequencies of 250, 500, 1000, and 2000 Hz.
In order to increase the efficiency of a polystyrene silencer, considering economic conditions and the desired location, greater thickness of polystyrene can be used. In addition, correct design of the hole on the silencer walls results in an increase in sound insertion loss outside the silencer.