The above figure shows the step response computed from the fluid-dynamic synthesis procedure (solid curve) plotted against the impulse response computed by a linear acoustic synthesizer (dashed curve). Note the strong correlation between peak frequencies. The amplitude roll-off for the Navier-Stokes solution is expected since it is generated from a step response rather than an impulse response like the linear acoustic result. This derivative relationship results in a 1/frequency factor (~6 dB/octave) roll-off in the N-S result.