Sound transmission characteristics of loosely packed wood dust And wood chips for noise attenuation: A preliminary study

Abstract

This study investigates the sound transmission coefficient (STC) of loosely packed wood dust and wood chips as potential organic materials for sound insulation. The STC was determined by measuring the transmission loss (TL) through cubical-shaped boxes filled with the test material. The packing uniformity was ensured by using two meshed cubes (60×60 cm2 on each side, 5 cm thick) to secure the material. A B&K type 4292 omnidirectional speaker and a type 2734 amplifier were, placed at the cube's center. Sound pressure level (SPL) measurements were conducted using a B&K type 2250 class 1 sound level meter inside and outside the cube, with average values taken from measurements on four sides. The study employed pink noise (12.5 Hz – 20,000 Hz) in one-third of octave bands for the investigation. TL and STC were calculated independently for wood dust and chips. Results indicate a significant dependence of TL on particle size and sound frequency. Minimal attenuation was found for frequency below 400Hz for wood chips and below 80 Hz for wood dust. Sound with higher frequencies experienced substantial attenuation for both materials. The STC of loosely packed material was found to be highly dependent on particle size, with smaller particles promoting higher absorption and higher TL, resulting in lower STC. The STC for loosely packed wood dust is less than 0.05, while the same for wood chips vary between 0.3 and 0.4 across a wider frequency range. In comparison, commercially available solid wood panels have an average STC of 0.04 in this frequency range, indicating compatibility with our results for wood dust but with higher reflection. The study suggests that using loosely packed, durable organic materials can offer a sustainable and aesthetically pleasing alternative in the acoustic insulation industry, potentially positively impacting human health and well-being.