diff --git a/backends/PalmOS/Src/palm.cpp b/backends/PalmOS/Src/palm.cpp
index d6a4b5e4fb7..7fb2164ef0e 100644
--- a/backends/PalmOS/Src/palm.cpp
+++ b/backends/PalmOS/Src/palm.cpp
@@ -1131,6 +1131,7 @@ void OSystem_PALMOS::play_cdrom(int track, int num_loops, int start_frame, int e
 		if (start_frame == 0 && end_frame == 0) {
 			MsaPlay(_msaRefNum, _msaTrack, 0, _msaPBRate);
 		} else {
+			// MsaTimeToSu doesn't work ...
 			_msaTrackStart = (UInt32) ((float)_msaStartFrame / ((float)fullLength / (float)SU));
 			MsaPlay(_msaRefNum, _msaTrack, _msaTrackStart, _msaPBRate);
 		}
@@ -1320,6 +1321,10 @@ bool OSystem_PALMOS::set_sound_proc(SoundProc *proc, void *param, SoundFormat fo
 	return _sound.active;
 }
 
+void OSystem_PALMOS::clear_sound_proc() {
+	_sound.active = false;
+}
+
 void OSystem_PALMOS::check_sound() {
 	// currently not supported
 	// but i need to use this function to prevent out of memory
diff --git a/backends/PalmOS/Src/palm.h b/backends/PalmOS/Src/palm.h
index 7cdc6376863..8c6e8b442d7 100644
--- a/backends/PalmOS/Src/palm.h
+++ b/backends/PalmOS/Src/palm.h
@@ -85,8 +85,24 @@ public:
 	
 	void SimulateArrowKeys(Event *event, Int8 iHoriz, Int8 iVert, Boolean repeat);
 
-	// Set function that generates samples 
+	/** @name Sound */
+	//@{
+	/**
+	 * Set the audio callback which is invoked whenever samples need to be generated.
+	 * Currently, only the 16-bit signed mode is ever used for Simon & Scumm
+	 * @param proc		pointer to the callback.
+	 * @param param		an arbitrary parameter which is stored and passed to proc.
+	 * @param format	the sample type format.
+	 */
 	bool set_sound_proc(SoundProc *proc, void *param, SoundFormat format);
+	
+	/**
+	 * Remove any audio callback previously set via set_sound_proc, thus effectively
+	 * stopping all audio output immediately.
+	 * @see set_sound_proc
+	 */
+	void clear_sound_proc();
+	//@} 
 
 	// Poll cdrom status
 	// Returns true if cd audio is playing