Translation:I washed my hair in the bath.
I wouldn't call it stress so much as pitch; stress would imply both a pitch shift upward and syllable lengthening. The Japanese language is a mora timed language and not stress timed like English, meaning all syllables are spoken with the same amount of time. This means it is also a pitch accented language, meaning the pitch you use determines which regional dialect you're speaking.
That said, a number of homonyms will have different pitches depending on the dialect, and such patterns determine which word/semantic meaning you want to use. Of course, if you speak with an accent, the listener should still comprehend based on context.
For those interested, there is a whole article on Wikipedia devoted to this so-called ”Japanese pitch accent”.
Thank you for bringing this up! I clicked on the discussion to warn people, but you beat me to it.
Let me emphasize this point to everyone reading: Do NOT dunk your head in the おふろ, The reason is that it would be disgusting if everyone shared dirty water. Get yourself clean using little tubs and your soap and shampoo BEFORE you get into the おふろ. You will sit on a tiny stool next to a faucet. There is a drain in the tiled floor, so you just keep dumping water over yourself until you are clean. Then, you can climb into the hot おふろ and just soak and relax. Don't dunk your head, because then you might leave strands of hair floating around, which is gross. Oh, and be prepared to socialize.
If you're in someone's home and the おふろ is a one-person deal, you will probably be offered the first shot (since you are a guest). Don't drain the tub. Think of it this way: It takes a lot of energy to heat the water. So this is why this bathing ritual evolved. Get clean first, enjoy the soak, and then let the next person have the clean hot water.
You're right, but I think it's the English translation that's the problem, while the Japanese is fine. 風呂 (furo) is a shower room with a bathtub, not specifically the bathtub itself. You can wash your hair outside of the tub (there's a drain in the floor) and still be in the お風呂.
There isn't a definitive difference in Japanese and most of the time when it rejects one and accepts the other, it's just a lack of having added the one marked wrong as a possible answer. In this sentence, either would work, though "the bathroom" would generally be used in American English to imply that it was the bathroom that was in your vicinity at the time.
That said, it would usually be more appropriate to use "the" with something marked with は as the topic, and "a/an" with something marked with が as the subject. This is because the topic must be about a specific thing that is assumed to be known.
(A bird appears flying near two people.) Person A: とりがよびます "A bird flies." or "Birds fly." Person B: とりはどこですか "Where is the bird?" or "Where are the birds?"
Person A uses が to mark the bird as the subject performing the action of flying because the bird hasn't been previously identified or encountered by the speakers. Person B, however, uses は to make the bird the topic since the bird has now been identified and Person B wants to discuss that specific bird. If Person B had used が instead of は, the second sentence could easily be taken to mean "Where is a bird?/Where are birds?", asking more about the presence of any birds, rather than the specific bird that Person A identified.
Also note that "とり" doesn't denote how many, so it could refer more than one bird, in fact, Person A could use it to refer to one bird and Person B could think it was meant in the plural sense, and use it as such. The reverse could also happen.