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The nonlinearity parameter (B/A) of a fluid-like media could be useful to assess structural changes, e.g., for tissue identification. To estimate the B/A, the 2nd harmonic generated signal recorded using a dual transducer could be used. However, in many instances, only the fundamental band signal acquired, for example with a clinical linear array transducer, might be available. In our approach the 2nd harmonic is related to the depletion in the fundamental band signal when comparing echo signal envelopes collected using two different excitation pressures: low and high. Specifically, we use the energy conservation principle by relating the 2nd harmonic to the loss of power at the fundamental band as it propagates in lossy media. Our method assumes that for propagation in a lossy medium, energy from the fundamental band is transferred mainly to the 2nd harmonic, and that propagation at low power settings are …