@Override
    public void read(JmeImporter im) throws IOException {
        super.read(im);
        InputCapsule ic = im.getCapsule(this);
        volume = ic.readFloat("volume", 1f);
        highFreqVolume = ic.readFloat("hf_volume", 1f);
    }
Sets the overall volume.

@param volume the new overall volume scaling (0.0 - 1.0).
@throws IllegalArgumentException if {@code volume} is out of range.
jme3-core/src/main/java/com/jme3/audio/LowPassFilter.java