<map version='1.0.1'>
<node TEXT='Sound Waves'>
<node TEXT='Characteristics'>
<node TEXT='Pitch'/>
<node TEXT='Loudness'/>
<node TEXT='Timbre'/>
</node>
<node TEXT='Propagation'>
<node TEXT='Reflection'/>
<node TEXT='Refraction'/>
<node TEXT='Diffraction'/>
</node>
<node TEXT='Applications'>
<node TEXT='Musical Instruments'/>
<node TEXT='Sonar'/>
<node TEXT='Ultrasound'/>
</node>
</node>
</map>