Ultrasonic Wave Attenuation Basics for Paperboard Creasing Quality
Non-destructive ultrasonic wave attenuation evaluates paperboard crease quality by measuring acoustic energy loss caused by internal shear delamination.
Ultrasonic Attenuation Coefficient
Acoustic Metric
Material characterization using high-frequency sound waves quantifies the rate of acoustic energy dissipation as an ultrasonic pulse propagates through a structured medium. In paper and paperboard testing, ultrasonic attenuation coefficient measures the exponential rate at which wave amplitude decays per unit distance through the anisotropic fibre matrix. The metric captures acoustic energy losses caused by viscoelastic absorption within cellulose fibres and sound scattering at microscopic air-fibre interfaces throughout the sheet.
Property Correlation
Structural variables within paperboard directly determine the magnitude of acoustic energy loss during wave transmission. As ultrasound travels through a multi-ply board, the ultrasonic attenuation coefficient increases in proportion to substrate porosity, unrefined mechanical pulp content, and internal micro-void volume. Dense, highly refined chemical pulp sheets with low void fractions exhibit minimal acoustic scattering, yielding low attenuation values.
High-bulk paperboards containing unrefined mechanical fibres and mineral fillers scatter sound energy heavily at internal phase boundaries, producing high attenuation rates. Measuring this parameter along the thickness direction allows online sensors to detect variations in sheet density, moisture content, inter-ply bonding strength, and internal delamination flaws without contacting or destroying the moving web.
Signal Processing
Automated web inspection systems record baseline attenuation values across virgin and recycled paperboard grades to monitor manufacturing consistency. Sudden increases in attenuation signal internal structural defects, such as blister formation or poor ply bonding, enabling converting operators to isolate defective reels before carton scoring.