Add debris explosion sound.

This is one of the two sounds played when debris from a large object (like an
asteroid or boss) explodes. This one uses a random spline function instead of
filtered noise

sound/Makefile

@@ -1,4 +1,4 @@
-SFX = plasma explode explode2
+SFX = plasma explode explode2 explode3
 OGG = $(SFX:%=%.ogg)
 WAV = $(SFX:%=%.wav)
 

sound/explode3.csd

@@ -0,0 +1,26 @@
+<CsoundSynthesizer>
+<CsInstruments>
+sr = 48000
+ksmps = 32
+nchnls = 1
+0dbfs = 1
+
+; Explosions
+; Noise generated by spline interpolation through random points.
+; p4: attack time (s)
+; p5: minimum spline point frequency
+; p6: maximum spline point frequencyy
+
+instr 1
+	k1 linseg 0, p4, 1, p3 - p4, 0
+	k2 linseg p5, p4, p6, p3 - p4, p5
+	a1 rspline -k1, k1, p5, k2
+	out a1
+endin
+</CsInstruments>
+<CsScore>
+i 1 0 2 0.01 100 20000
+e
+</CsScore>
+</CsoundSynthesizer>
+