Noise levels of a peanut dryer in an open shed with and without a muffler

Authors: McIntyre, Joseph; Cook, Hunter

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2023
Publication Date: 12/7/2023
Citation: Mcintyre, J.S., Cook, H. 2023. Noise levels of a peanut dryer in an open shed with and without a muffler. Peanut Science. 50(1)P.22-28. https://doi.org/10.3146/0095-3679-501-PS22-13.
DOI: https://doi.org/10.3146/0095-3679-501-PS22-13

Interpretive Summary: Harvested peanuts must be dried to prevent spoilage in storage. Peanuts are dried using forced hot air dryers that produce a great deal of noise while operating. In recent times residential populations living near peanut drying facilities have increased and are now raising serious community objection to nuisance noise levels. In an effort to abate dryer noise a cylindrical sheet metal muffler lined with fiberglass was designed, fabricated, and tested. Test results indicated a muffler attached to the air intake of a dryer could reduce dryer noise to the OSHA permissible level of 90 dBA for an eight hour time period to protect the hearing of workers. The muffler reduced noise levels at 4.5 m (14.75 ft) from the side of the dryer to just less than 85 dBA the level above which OSHA recommends employers initiate hearing conservation programs. Sound levels at 23 m in front of the dryer were reduced to 69.3 dBA which is equivalent to classroom chatter. Study results suggest that further noise reduction is possible through redesigning the muffler using natural harmonics of the dryer/muffler structure, new tuned noise damping materials, and designing for sound resonance effects.

Technical Abstract: Harvested peanuts must be dried to prevent spoilage in storage. Peanuts are dried using forced heated air dryers that produce a great deal of noise while operating. In an effort to abate dryer noise, a cylindrical muffler was designed, fabricated from sheet metal, and tested. The muffler was 1.17m in diameter and 0.61m in length and was lined with 0.55m of R 30 fiberglass batting. Five configurations of the muffler were tested and the most effective one was the two inline mufflers attached to the air intake of the dryer. The two inline mufflers were found to reduce noise 4.5m in front of the dryer intake to the OSHA permissible level of 90 dBA for an eight hour time period. The inline lined mufflers reduced noise levels at 4.5 m from the side of the dryer to just less than 85 dBA the level above which OSHA recommends employers initiate hearing conservation programs. Sound levels at 23 m in front of the dryer were reduced to 69.3 dBA which is equivalent to classroom chatter. Though the muffler designed in the study reduced dyer noise to acceptable levels, study results suggest that further noise reduction is possible by redesigning the muffler using natural harmonics of the dryer/muffler structure, new tuned noise damping materials, and designing for sound resonance effects.