* He mumbled a response, too embarrassed to speak clearly. (This emphasizes the speaker's lack of confidence or discomfort.)
* The old man mumbled something about the weather, but I couldn't understand him. (This highlights the difficulty in understanding the speaker due to their unclear speech.)
* She mumbled a quiet "thank you" before rushing out the door. (This illustrates a hurried and possibly shy expression of gratitude.)
* The teacher's voice was barely audible as she mumbled the instructions. (This emphasizes the speaker's quiet and unclear delivery.)
* He mumbled a protest, but it was drowned out by the cheers of the crowd. (This emphasizes the weakness of the speaker's voice in comparison to the surrounding noise.)
Let me know if you'd like to see more examples!