How to reproduce:
1. Open given Unity project
2. Enter "TestTimelineCrumb" scene
3. Open Timeline window
4. Select "MasterSequence" game object in the hierarchy
5. Set Control Track(1) ControlPlayAbleAsset speed to 1
6. Play it in the Timeline
- The sound is working correctly
7. Set Set Control Track(1) ControlPlayAbleAsset speed to 3
8. Play it in the Timeline
- Sound disappears

Expected result: Sound should be working in both ways
Actual result: Sound is working only then when speed is set to 1

Reproducible with: 2018.2.0a9-2018.2.0a4

Note:
In 2018.2.0a3 and earlier versions sound disappears even when speed multiplier is set to 1
Repro video is below