I used to listed to Canadiens games, though I speak no French and don’t follow hockey, because the announcers sounded like Bob and Doug McKenzie speaking French. [del]Hilarious![/del] Interesting from a linguistic point of view.
Absolutely. If I’m talking to kids, I try and speak their language - American English, rather than my native Australian drawl. If I was to say, “hey kiddo, please put your rubbish in the bin,” they wouldn’t get it, at least not right away. Whereas if I say through my nose, “Jordan, put your trash in the trash can!” they get it, and they do it.
My Aussie family say I sound like a Yank. New acquaintances ask if I’m “from England or something?” Depends on the situation.
I code-switch constantly. Mostly without thinking about it, but sometimes I do it on purpose. American regional accents I can do pretty well, but foreign accents all end up sounding Dick Van Dyke Cockney or B-movie Italian.
I too find myself inadvertently matching the dominant accent of my audience or of the location – in both Spanish and English – but not in all instances. Sometimes it sticks and sometimes it doesn’t.
I know people do this, but I try not to. Every once in a while I catch myself accenting a word like a Wisconsinite (I’m from New York, but have lived here since 2000) and I want to chew my tongue off to make sure it never happens again.
For some reason, it gets under my skin when someone goes on vacation for a week and comes back talking like a different person. Dude, I know you. You’re not from Jersey.
Just spent a week in England. It was brilliant. Cheers!
Yes. I made a comment recently about how a lot of people in the Northeast think my accent is Southern and was promptly told “you don’t have one”. So apparently I use neutral American when I’m in the green room doing community theater, and slip southward when I’m tired and trying to argue sense into someone. 
My accent is approximately Kantou in Japanese, but I change register a lot instead. Excess formality tends to be parsed as sarcasm, so I often start there and then drop into informal bokukko speech to make my point or deliver a punchline. Otherwise, I wouldn’t sound like me.
Northeast/Southern…Japan? 
I have a “polite” voice with good grammar and fairly neutral rural Illinois twang, and I have a “redneck” voice with poor grammar and a heavy twang bordering on a Southern drawl depending on where I am. If I’m at someplace like church or at somebody’s house for dinner. it’s the former. If it’s at work or on my dad’s farm, it’s the latter.
Not according to linguists I have known, nor to wiki: Code-switching - Wikipedia. I have always understood it to me switching in mid-sentence from one language to another. I first heard about it in the context of totally bilingual Spanish kids in NYC, but it is also common among French Canadians. It is subject to some rules: for example, each phrase must be a grammatical phrase in whichever language it is in.
That’s not the definition I’m familiar with. At least not the only definition I’m familiar with. It also refers to dialectical transitions in language. For example, switching from whatever would be termed as “Standard American English” to, say, a dialect like AAVE (African-American Vernacular English) or back. I’m not sure I’ve ever heard of accent changes being referred to as “code-switching,” but it seems to be in the same linguistic ballpark.
I am Canadaian, and like to think I don’t have an accent, but of course I do. I don’t specifically hear it in my family, but I just spent a month in Northern Ontario, and noticed that some of my vowels and intonations had “changed” or more likely shifted back.
For example: Camp. Which in Northern Ontario could be a million dollar chalet, or an RV that is 30 years old and no longer runs, sitting on a plot of land. Or anything in between. A month back there and camp suddenly is elongated and comes out more like kay-yam-p. That word can get drawn out more than “Change” in “Freebird”.
Yeah, I don’t think it needs to be “switching in mid sentence” at all. Just adjusting your accent (or dialect) depending on your audience.
I once entertained an interesting family. Grandfather is Scottish, as is daughter, but daughter lived mostly in London. Grandkids grew up in the US.
Grandfather always spoke with a Scottish accent.
Daughter normally spoke with an English accept, but switched to Scottish accent when talking to her dad (grandfather).
Grandkids spoke with typical American accent when speaking to each other, but switched to English accent when talking to mom or grandfather.
This was all in the same setting, one afternoon in my house, not multiple settings. It was simply fascinating to watch!! And they, of course, were completely unaware they were doing it.
The question (your question) which I answered was not whether “the OP had asked about code switching” but whether “code switching only refers to language”. They are two different questions.
It is common to semi-consciously modulate your voice and mannerisms to match your audience. This is a sign of respect. Going too far, though, you may trigger suspicious of flattery or mockery.
Mine does, definitely. Slower and clearer sometimes, more southern others, etc.
I became acutely aware of this phenomenon when I was married to a man from Yorkshire. Once when we were visiting his parents, I overheard him talking to his mom and her replying in accents so broad I couldn’t understand a word. When they saw me, they immediately (and I think unconsciously) reverted back to the more understandable accent they typically used around me, the token American in the house.