Since the phonetic representations of the diphthongs in words like "house" and "why" are /aʊ/ and /aɪ/ respectively, I would like to know the name of the first vowel that composes these sounds. In other words, what's the name of the vowel that starts both diphthongs? Is it the short o as in "hot" or the short a as in "apple"? I ask because I often hear a nasal sound when native English speakers (especially from the US) pronounce words like "out" or "house," and this makes me think that the starting vowel might be /æ/ as in "anthem" rather than /a/ as in hot — I guess /a/ is a short o. Is my observation correct and Americans pronounce the diphthong /aʊ/ starting with /æ/? Could you please clarify what is the name of this /a/ sound in English? Is it simply an "a" in general? How do you pronounce the /a/ at the beginning of both /aʊ/ and /aɪ/? Does it sound like a short o /ɒ/ as in "hot" or like a Spanish a \ä\ as in "car"?
Also, I stumbled across a website that explains the pronunciation of these diphthongs in a way that confuses me even more:
/aʊ/: "This diphthong is pronounced as a short A sound sliding into an "oo" sound."
Is the initial vowel really a short a, and does it slide into an "oo" long u /o͞o/ as in "food" or into a short u /ʊ/ as in book?
/aɪ/: "This diphthong is pronounced as a long I sound sliding into a long E sound."
Does it really start as a long I sound? Does it really slide into a long E sound or maybe into a short I sound as indicated by the symbol /ɪ/?