with the direct pressure at the crest as used by maekawa with the frequency resolution used in the fft there are three spectral components in the third octave band centered at 2500 hz five at 500 hz and eight in the 10 000 hz band in this case in order to show the power of the impulse technique a 9 edged ramshackle barrier is studied fig9 for this case the 512 largest impulse samples are used at intervals of 25 microseconds the ground is assumed to be absorbent so that the mirror image does not exist the print out of the impulse response in the case of receiver r2 not plotted shows that the maximum impulse of magnitude 30 5 arbitrary units travels over the horizontal edge 4 just above r2 see fig9 the next largest is the impulse of strength 6 1 via vertical edge 9 and the third largest has strength 4 2 and is for the impulse that travels over vertical edge 1 receiver r3 obtains its major contributions differently the largest amplitude is 12 5 for the path over edge 6 the next largest is 8 0 via edge 9 and the third largest is 6 4 via edge 4 in general the maximum impulses occur for least time paths over diffracting edges the off set edges make smaller contributions the gross spectral response of the ramshackle barrier decreases at roughly 3 db octave but there are important variations that depend on the receiver position fig9 receiver.