raster image of media-alevel-206-t

Test on audio-level inheritance in several child elements. audio-level on the first element is 0.5. audio-level on the second sound is halved to 0.25. audio-level on the third and fourth sounds are halved agian to 0.125 and 0.0625 respectively.

If the user agent does not support the WAV media format, the test is still a pass.