control volume of the player - crackling noise

Hi there,


I want that my spaceship gets louder when my mouse moves away from it (and vice versa). Problem is that my function produces an annoying crackling sound I can't get rid of when I move my mouse away from it (and vice versa). The sound file is ok so far. Can someone help me out with this problem, please?

Code:

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shipSpeed = (abs(player.x - playerPrevPt.x) + abs(player.y - playerPrevPt.y)) / 2;//the ship's speed gets calculated
               
    //this is used to determine whether the ship's volume of its sound shall be increased or decreased
    if (shipSpeedPrev < shipSpeed) {
        sndManager.increaseSound(Main.SOUND_BACKGROUND, false, .01);
        } else if (shipSpeedPrev > shipSpeed) {
        sndManager.decreaseSound(Main.SOUND_BACKGROUND, false, .01);
        } else if (shipSpeedPrev == shipSpeed) {
       
        } else {
       
    }
               
    shipSpeedPrev = (abs(player.x - playerPrevPt.x) + abs(player.y - playerPrevPt.y)) / 2;//this is another ship speed so I can compare them

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//the decreseSound-function is almost the same

Code:

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public function increaseSound(soundName:String, isSoundTrack:Boolean = false, steps:Number = .1, targetVol:Number = 1):void {
            if (isSoundTrack) {
                if (soundTrackChannel != null) {
                    musicVolumeAdj.volume += steps;
                    if (musicVolumeAdj.volume >= targetVol) {
                        musicVolumeAdj.volume = targetVol;
                    }
                    soundTrackChannel.soundTransform = musicVolumeAdj;
                }
            } else {
                soundVolumeAdj = new SoundTransform(incrSndVal, 0);
                incrSndVal += steps;
                soundVolumeAdj.volume += incrSndVal;
                if (soundVolumeAdj.volume >= 1) {
                    soundVolumeAdj.volume = 1;
                }
                soundChannels[soundName].soundTransform = soundVolumeAdj;
                //trace("soundVolumeAdj.volume " + soundVolumeIncrAdj.volume);
            }
        }

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