public void setHighFreqVolume(float highFreqVolume) {
        if (highFreqVolume < 0 || highFreqVolume > 1)
            throw new IllegalArgumentException("High freq volume must be between 0 and 1");

        this.highFreqVolume = highFreqVolume;
        this.updateNeeded = true;
    }
Sets the high-frequency volume.

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