Check your engine timing. If it only happens when you accelerate and it sounds like a ticking, it means that the timing is out. It can become very expensive, you can burn the valves, or even melt a hole in your pistons.
You can also check your engine mounts and see if the engine moves a bit when you accelerate and something ( like the exhaust) is touching the body.
Other thing that it could be are your CV joints. They need to be checked by an expert, but if you feel a vibration in the steering wheel when the sound happens, chances are that its the problem. You can also turn the wheel and slowly accelerate and listen then.
Other sounds when accelerating can be a broken piston, or piston ring, but that will be accompanied by smoke, or the main bearings are going.
Bottom line, either turn the stereo up while driving, or see a mechanic.
Sorry I can't be more helpful