Experimental and Semi-Phenomenological Investigation on Sound Absorption Performance of Natural Granular Sound Absorber: A Case Study on Rice Bran Composites

The sound absorption performance of rice bran composites was quantitatively investigated through an improved semi-phenomenological approach. Rice (RB) employed as the primary and structural component in creation granular-type absorbers with urea-formaldehyde (UF) adhesive. coefficient (SAC) measured by two-microphone impedance tube method. Samples a per volume ratio lower than 253 kg/m3 show peak-valley characteristics saturation region their SAC spectrum. Five non-acoustic parameters for each sample were obtained direct measurement fitting experimental SACs to Johnson-Champoux-Allard (JCA) equivalent fluid model using least-squares higher proportions RB demonstrate porosity (ϕ), viscous characteristic length (Λ), thermal (Λ'). Flow resistivity (σ) only parameter that noticeably increases when increased while tortuosity (α_∞) did not strong correlation. For uncertainty analysis SAC, multivariate method used this study. A new (NM) predicated on power-law relation introduced Delany Bazley, which function flow alone. predicted more precisely standard Delany-Bazley (¯Δ_"abs(DBM)" ≈4.0¯Δ_"abs(NM)" ). proposed had potential be extended into unified empirical granular-typed future investigations broader spectrum granular materials.