diff --git a/src/processing/sound/Env.java b/src/processing/sound/Env.java
index e19e66a..bf03100 100644
--- a/src/processing/sound/Env.java
+++ b/src/processing/sound/Env.java
@@ -23,14 +23,14 @@ public Env(PApplet parent) {
 	* @param input Input sound source
 	* @param attackTime Attack time value as a float.
 	* @param sustainTime Sustain time value as a float. 
-	* @param sustain Sustain level value as a float.
+	* @param sustain Sustain level value as a float. (as fraction of the input amplitude)
 	* @param releaseTime Release time value as a float.
 	**/
 	public void play(SoundObject input, float attackTime, float sustainTime, float sustainLevel, float releaseTime) {
 		SegmentedEnvelope env = new SegmentedEnvelope(new double[] {
 				attackTime, input.amp, // attack
 				// gradual decay towards sustain level across entire sustain period
-				sustainTime, sustainLevel, // sustain
+				sustainTime, sustainLevel * input.amp, // sustain
 				releaseTime, 0.0 });
 
 		// TODO re-use player from fixed or dynamic pool