0 ACLEAR()

0 OP = AUNIT(A_OUTPUT,,A_ENVFIXED)
0 OUTOP = OP

0 LOOP I, 500
0 OP = AUNIT(OP,,A_ENVFIXED)
0 AFILPOINT(OP, A_FILFW, 0, 0)
0 AFILPOINT(OP, A_FILFW, 15, 1024)
0 LOOPEND

0 AADDOUT(OUTOP, OP, 512)

# sound source

0 OP = AUNIT(OUTOP,,A_ENVFIXED)
0 AOSC(OP)
0 AENVPOINT(OP,, 0, 1024)
0 AENVPOINT(OP,, 180, 0)
0 AFILPOINT(OP, A_FILFW, 0, 1024)

0 APLAY("T60CDEC1",,, "echo.wav")
