Are the words "Aural" and "Oral" usually pronounced the same? Does it vary by dialect? Are there strategies that people use to differentiate them when listening to spoken English?
Are the words "Aural" and "Oral" usually pronounced the same?
Does it vary by dialect?
Judging by the answers and comments here, they do do. That said, these differences appear to be idiosyncratic rather than by accent. The OED, whose IPA I have used below, suggests that in other accents (AE) the pronunciation of both words is as homonyms
Are there strategies that people use to differentiate them when listening to spoken English?
Yes. They include context. If you are deaf and go for an aural examination, it is clear what is meant as nobody is going to look in your mouth – likewise the dentist is not going to look in your ear.
I came across the difference in school when aural and oral exams were announced.
Oral was always pronounced oral /ˈɔːrəl/ as this was the commonest type and the default.
Purely to emphasise the difference where context was lacking, aural was occasionally [mis]pronounced owr’l /aʊrəl/ but, in deference to the strange pronunciation, the speaker would often point to their ear.
As far as examinations were concerned, quite early on, the phrase “[aural] comprehension exams” took the place of aural exams – and then the word “aural” was abandoned, and then the oral exam became "the spoken exam".
My accent is East Midlands with influences of Yorkshire moderated with some RP and I can detect no difference between oral and aural when I speak and when I listen to other people - all rhyme with choral /ˈkɔːrəl/ but not coral /ˈkɒrəl/.
Aural and oral are “supposed” to be pronounced the same in almost all accents of English (the exception would be accents without the “north-force merger”). Most dictionaries do not give distinct pronunciations for these two words. Although it's not unheard of for people to pronounce them differently, distinguishing them by sound usually involves the use of some pronunciation that could be considered a “mispronunciation”.
Aural has the long north vowel as the outcome of the thought vowel before /r/
Words spelled with "au" followed by "r" are not that common, so it's a little hard to describe their pronunciations in terms of a general rule. But aura, dinosaur, Minotaur, centaur, thesaurus, tyrannosaurus are other words where "aur" is standardly pronounced as the vowel found in north.
Laurel has a pronunciation with the "short o" vowel in British English, /ˈlɒrəl/, which can be considered irregular. (A few words spelled with au before another consonant also have irregular pronunciations with "short o" in British English, such as sausage /ˈsɒsɪdʒ/.)
As mentioned in David Robinson’s and Greybeard's answers, aural is sometimes pronounced with the sour diphthong. The phonetician John Wells made a blog post mentioning the "ˈaʊrəl" pronunciation of aural, and the comments below it have some more discussion: "trauma", John Wells's Phonetic Blog.
Anecdotally, for some American English speakers it is possible to pronounce aural with the vowel of caught (i.e. pronouncing the first syllable like the word "awe"), contrasting with the vowel in oral. See the forum posts here: http://www.verduria.org/viewtopic.php?f=4&t=73&start=200 as well the comments left beneath your question by Hot Licks and choster. For a speaker who merges cot and caught as an unrounded vowel, this could be aural [ɑrəl] vs. oral [orəl], or for a speaker who has the north-force merger but no unrounding of the vowel in caught, this could be aural [ɔrəl] vs. oral [orəl].
Oral has the long force vowel as the outcome of the "long o" vowel before /r/
Oral is an -al adjective, a class of words that come from Latin and that generally are pronounced in a way consistent with the "traditional English pronunciation of Latin words". In the case of oral, the relevant part of the traditional Latin pronunciation rules is a rule saying that a vowel letter takes its "long" pronunciation when it comes in the second-to-last syllable of a word and is followed by only a single consonant letter. Since the O in "oral" meets both of these criteria, it is regular for it to be pronounced as a "long o" sound, which before a /r/ is normally realized as the force vowel.
There are some exceptions to the traditional pronunciation rules: the most relevant one is moral, which British English speakers pronounce as /ˈmɒrəl/, with a "short o" sound. (Coral also has a "short o" in British English pronunciation, but it is not an -al adjective.)
Oral doesn't seem to be a well-established exception, but it sounds like a few British English speakers make it /ɒrəl/, rhyming with moral and coral. Aside from Tony Mountifield's answer, which seems to be saying this, the Teflpedia article "Pronunciation exercises: /ɒrV/ vs /ɔːrV/" points out that the Collins Dictionary entry for "oral in British" lists the variant pronunciation /ˈɒrəl/ after /ˈɔːrəl/.
Since this question asks about whether people can tell the difference I am going to answer for myself and my dialect rather than referring to a dictionary.
I speak Standard Southern English English and I pronounce them the same as far as I know. I cannot tell the difference when I hear them whatever accent the speaker has.
There is one exception and that is that I sometimes hear aural with the same vowel as now. Sometimes it is clear they are deliberately pronouncing it that way to distinguish it but sometimes I am not sure if they know how to pronounce it.
I never hear them pronounced slightly differently.
I have always lived in Southern England, and am a bit of a language pedant. I don’t know if others would consider it correct, but I always distinguish by pronouncing aural like choral, and oral like coral. I hate it that so many pronounce them both like choral. And pronouncing aural like “owral” makes it sound like a German word.
I’d say that in America they’d most likely be pronounced the same, whereas in England the difference is more readily apparent to the person hearing this. Certainly, as one from Southern England I’d say this is true, as I believe some understanding is lost when not making clear the difference. I feel it (pronouncing them the same) is effectively bastardizing the language.