Because there will be some beam divergence from any real, finite source, the program, bamp, makes a correction for beam divergence before measuring inelastic decay. Currently, the only option is for a spherical divergence correction. Under this model, the amplitude, A, of a spherically divergent wave at distance, r, from the source is given by
where is the amplitude at a reference offset . Here, amplitude is the particle velocity as measured by a moving coil velocity phone (dynamic stress/impedance). The decay at any frequency may be expressed in terms of (1/m, also sometimes referred to as nepers/m). Alternatively, decay may be expressed in decibels as Program, bamp, writes the measured inelastic decay, , at each frequency and writes the results to a file, bamp.his, which is later read by cainv3.m.