A plastic waste processing plant had a problem with noise exposure exceeding the permissible noise standards at workplaces. The analyzed part of the plant consisted of two halls: an extruder hall and a mixing hall.
Measurement and analysis
At the beginning, KFB dealt with testing the existing stage. Sound level meter, an acoustic camera and a reference omnidirectional noise source were used for the measurements. The sound level was measured at fixed points according to a developed grid of points in the halls, at intervals of approximately 3-4 m, then the noise exposure level was measured in specific places where employees were located.
Then, measurements were made with an acoustic camera to identify the main noise sources in the extruder hall and the mixing area. In the next stage, we took measurements from up close the main noise sources in order to determine the acoustic power level of each source.
The last stage of that part was taking measurements using a reference omnidirectional noise source to determine the acoustics of the interior of the “extruder” hall and the “mixing” area for the purpose of calibrating the analyzed areas in the simulation program. The noise exposure level in the existing state was exceeded. Based on the measurements, an acoustic analysis was performed using an acoustic model of the studied areas.
Method and analysis
Thanks to the obtained results, we could now construct an acoustic model based on measurements of the hall geometry and data obtained from acoustic measurements.
The power level, hall geometry, results in the grid of points and noise exposure measurement are entered into a computer program, calculated in the acoustic model and calibrated.
The results allowed us to further develop the so-called ranking of sources; we also received data specifying how much we should reduce each noise source to bring the emission within the norm. The permissible noise exposure standard is 85 dB(A).
Having our data and analysis in place, we could now prepare the noise reduction strategy.
Solution
Within it, we propose specific solutions. In this particular case it was:
- Acoustic adaptation of the wall
- Screens in the Mixing area
- Screens in the extruder area
Then a concept is created, including graphics showing the target appearance of the rooms and the expected noise reduction at work stations.
The next stage is the development of an acoustic and technical concept based on the acoustic analysis and the implementation of the proposed measures.
After implementing our solutions, acceptance testing was made to verify the operation of the proposed anti-noise safeguards. Measurements were made at the same points as before the analysis. The noise exposure level after the implementation of acoustic protection was reduced to permissible levels.. The reduction value was between 4.3 dB and 2.2 dB.
The noise reduction measures not only addressed the noise problem but also improved the overall quality of the work environment, benefiting the health and well-being of employees at the plastic waste processing plant.