The propagation of ultrasound through a classical, dilute, monatomic gas has been previously studied in terms of the Boltzmann collision equation with the collision term replaced by the relaxation model∂f∂t]coll = −(f−f̄)τwheref̄was the displaced Maxwellian distribution in the presence of the sound wave and the relaxation time τ was assumed to be independent of the instantaneous particle velocityv. This model, although yielding the correct qualitative behavior at low frequencies, did not yield the classical result for the slope of the absorption curve. Rather than taking τ to be independent ofv, it is now assumed that τ −lvwhere the mean free pathlis nowvindependent. That this new model might yield some improvement in the slope of the absorption curve at low frequencies is suggested by the fact that model yields the correct ratio of the thermal conductivity to the shear viscosity: namely, (15/4)(K/m), as opposed to the result 5 (K/m) obtained on assuming τ to be independent ofv. Some slight improvement is obtained, but the classical absorption does not result. The reason for this is briefly discussed.