diphthongs and accents

[Scar504]

I often hear that Japanese is exclusively pronounced syllable by syllable (あ, お, い) as opposed to diphthongs like in English (strain, plain, beat etc.).

Is this really true? I certainly hear it in certain words. For instance, I can hear all the letters being pronounced individually in the name なお, but with other words, such as おぼえてる, it just sounds like "oboiteru."

Do native speakers of Japanese really individually pronounce each character in every word, or do they simply mix them into one sound? Is it permissible to pronounce words like おぼえてる　and かえる as "oboiteru" (oi as in boy) and "kairu" (ai as in die) respectively?

 

[YangMuye]

Whether diphthongs exist in Japanese or not is arguable, but some evidence seems to suggest that some syllables should be treated differently.


First, all syllables like あん, えん, いん, おん, うん, あー, えー, いー, おー, うー are not separable. No accent contrasts between あん and あ↓ん or between ↑ああ and あ↑あ.
Secondly, some あい, うい and あえ are not separable too.
Some researches show that, long vowels and diphthongs may be slightly shorter than two syllables.


For example: 先生は
せ↑んせ↓いは (accent in dictionary)
↑せんせ↓いは (accent often used)
↑せんせい↓は (accent often used)


帰(か↓え)る (irregular accent. The regular accent should be かえ↓る )
愛(あいす↓)る　→　愛(あ↓い)して (irregular accent. The regular accent should be あい↓して)

Do native speakers of Japanese really individually pronounce each character in every word, or do they simply mix them into one sound?

They can individually pronounce each character, even for words like せんせい. (nasal e and long e)

do they simply mix them into one sound

I think their diphthongs(no matter they are diphthongs or not) are at least different from English ones. English diphthongs are falling. The ending part of ie in die is not a vowel.

Is it permissible to pronounce words like おぼえてる　and かえる as "oboiteru" (oi as in boy) and "kairu" (ai as in die) respectively?

I think you cannot, at least you cannot do it intentionally.
But 会えて良かった sounds like あいてよかった when you speak fast.

 

[Tonky]

Is it permissible to pronounce words like おぼえてる　and かえる as "oboiteru" (oi as in boy) and "kairu" (ai as in die) respectively?

I don't really think so, but if that happens, it may be coming from some local dialects or maybe some subculture on-purpose word-play.
As far as I'm aware, おえ → おい does not happen in general.　(Unless you mean schwa instead of .)
（I've seen あい→あえ happen. There is a high school called 済美(さいび) that became famous for high-school baseball tournaments, and some locals call it さえび instead, and I believe it is originally schwa.)

Whether diphthongs exist in Japanese or not is arguable, but some evidence seems to suggest that some syllables should be treated differently.

I agree, but from a different point of view.

Take a look at Edo-dialect or Edo-ben/江戸弁・江戸っ子言葉. It changes a diphthong into a long vowel with their lazy mouths.
The most famous phrase 「台所にある買い物袋に大根が入っている」 is said to be pronounced as 「デードコロにあるケーモノぶくろにデーコンがへーってる」.
Other examples are, 「こいつは」→「こいつぁー」, 「手前（てまえ）」→「てめー」, 「～ない」→「～ねー」 and so on.
Nagoya dialect or Nagoya-ben/名古屋弁 has the similar tendency. The most famous phrases are 「エビフライ」→「エビフリャー」, 「（ど）えらい」→「（ど）えりゃー」.
They do recognize these "double vowels" as "diphthongs" and replace them with long vowels instead, which suggests that they recognize the existence of diphthongs even though they refuse to pronounce them.
Furthermore, they do use one diphthong intentionally very often, 「でいっ」 for 「だ（い）」, as in 「江戸っ子だ」→「江戸っ子でいっ！」

For example: 先生は
せ↑んせ↓いは (accent in dictionary)
↑せんせ↓いは (accent often used)
↑せんせい↓は (accent often used)

帰(か↓え)る (irregular accent. The regular accent should be かえ↓る )

I beg to differ here, though. Possibly local dialects intervening some speakers' accents, but the standard accent is always せ『んせ』いは and I myself never heard 『せんせ』いは nor 『せんせい』は. There are some dialects that allow you to say せん『せ』いは/せん『せい』は or せ』んせいは.
Also, please keep in mind that normal native speakers do not really think about how their own accents are (unless they have studied about them well) and they very often claim to have been using ones they aren't using.

か』える is 帰る and か『える is 変える but there is no かえ』る in standard accent. Even when spoken in Edo-dialect for 帰る, it will be け』－る)


All these said, let me remind you that we still always consider each vowel individually, especially when we count mora, say, for poetry like haiku.

 

[Scar504]

I see. Well, thank you both for your replies. I think it's difficult for nonnative speakers to both hear and pronounce each vowel independently; I just wanted to know how important it is to do so.