Ok, not “success” exactly. It all depends on your specific definition.
If by success you mean occasionally advantageous, then yes. Success.
I’ve come to the conclusion that if you don’t want to answer someone –– you don’t feel like explaining yourself, you don’t know the answer, etc. –– mumbling is a key mode of evasion. You, friends, can become awkward roadblocks in polite conversation. People are rendered defenseless by a mumbler. They simply don’t know what to do with you. They can say, “I’m sorry, what was that?” And if they receive a mumbled answer a second time, they are likely to abandon ship. They use easy escapes such as: “Oh, yes, of course” or “Hahah” or “It’s funny you should say that because here’s an entirely unrelated subject I’d like to bring up to resuscitate this conversation.”
Sometimes this tactic can work in the opposite fashion: Instead of getting you out of things, it can get you things. There are some people who just become so exasperated by you that they are willing to give you things. For free!
For instance, if you ride a bus and try to pay for a ticket with bills that require change, and the bus driver cannot procure said change until other riders get on, you will probably be kindly invited to sit down until the time comes. The bus driver will forget. And forget.When you arrive, you can try to remind the bus driver (because you have morals after all). But by that time, he/she just wants to get the passengers on their merry way. Though good intentioned, you complicate this. You wait until everyone else has piled off the bus and begin to explain yourself. “Oh, hello. You probably don’t remember me from back there on the bus, but you see, I haven’t paid, and you said to wait, so I’ve waited and here’s the $20 I’ve been clutching for two hours in anticipation of your demand of it!” You might think you sound abnormally loud after saying this mouthful, but he/she can’t hear you (bus terminals are loud, and you are a mumbler), and so he/she waves you away. “Oh, no see, I haven’t paid,” you can try again. He/she just waves more frantically. At this point, a customary thumbs up is a polite recognition of mutual understanding.
If this sounds too Raskolnikov for you, the other extreme, I’ve heard, works well for some people. If you yell everything, people think you are either very authoritative, passionate or crazy. Some comedians even work this technique like magicians––to create the illusion that they are funny. All misconceptions can be used to your advantage. Nearly all situations are appropriate. “YES OF COURSE I WOULD LIKE SALAD INSTEAD OF FRIES. WHAT SORT OF CRAZY PERSON DO YOU THINK I AM? DON’T YOU REALIZE THERE’S AN OBESITY EPIDEMIC IN THIS COUNTRY?!”