Signal Loss
The reduction in amplitude of a sound wave as it travels through a solid material indicates the internal structure and viscoelasticity of the medium. In paper testing, ultrasonic attenuation describes the rate of energy loss as an acoustic pulse passes through the paper sheet. This metric is measured using non-destructive high frequency transducers.
Paper Characterization
This energy loss occurs through a combination of scattering at the fiber boundaries and absorption within the viscoelastic fiber network. Because ultrasonic attenuation is highly sensitive to the density, moisture content, and refining degree of the pulp, it provides a detailed picture of the paper’s internal structure. If the paper contains micro cracks, voids, or uneven fiber distribution, the sound wave will be scattered more intensely, leading to a higher attenuation rate.
This measurement is used for identifying structural defects in the web.
Web Inspection
Real time monitoring of this parameter on the paper machine allows operators to make immediate adjustments to the refining and press sections. When the ultrasonic attenuation departs from the target baseline, it indicates a shift in the physical properties of the paper that could lead to failures on high speed printing presses. By maintaining uniform attenuation across the entire width of the web, the mill can ensure consistent printability and stiffness.
This automated testing reduces the need for slow, destructive laboratory tests on finished paper reels.
