[HotZ28]

First, I would check the complete exhaust system for leaks, to determine if the "bass sound" could be coming from that area.
When the OBD II system detects a misfire that exceeds "normal" limits, it illuminates the Check Engine light and sets a P-code that corresponds to the misfiring cylinder. The last number in a P300 series code tells you which cylinder is misfiring. A code P304, for example, says cylinder number four is misfiring. At this point, you want to check the ignition secondary; i.e. coils, wires & plugs. If you also find a P204 code (P200 series codes cover the injectors), you'd know the misfire was probably caused by a bad injector.
If you find a P300 code, it means the misfire is random and is moving around from cylinder to cylinder. The cause here would likely be something that upsets the engine's air/fuel mixture, such as a major vacuum leak, leaky EGR valve or unusually low fuel pressure (weak pump or faulty pressure regulator). There's really no magic bullet for finding misfires. It takes a certain amount of detective work to isolate the fault and determine the underlying cause.