Spatial normalization of the high-frequency ultrasound energy loss in open-cell foams

Wide-band and air-coupled ultrasound pulses are propagated through slabs of open-cell reticulated solid foams and the transmission coefficient is measured. Under these conditions, fluid in the pores and solid skeleton are strongly decoupled; in addition, at frequencies well over that of the relaxation of the influence of the tortuosity, it is observed that energy loss approaches to a constant value: ∣γ∣∞. Internal surface area (Si) and the length dimension parameter (Λ) of the foams are independently measured. Results reveal that ∣γ∣∞ vs Λ or Si follows a power law very close to linear, suggesting a possible spatial normalization for ∣γ∣∞.