For a few weeks I have been studying the pronunciation of ん and all allophones.
there are many allophones, I was able to learn almost all of them. however there is a case where I have problems ん ＋ [s]
when ん is followed by a vowel, ん becomes a nasal vowel
権威 けんい [keĩi];
恋愛 れんあい [reĩai];
禁煙 きんえん [kiĩeN];
I have no problem with this. but in the video below it is explained that when ん is followed by fricative sounds like [s] and [h], it also becomes a nasal vowel
音声 おんせい [oĩse:];
感謝 かんしゃ [kaĩsha]
https://youtu.be/2Iv-M7tnm6Q?t=181 (3:01) and (3:06)
according to the video, ん of 感謝 and 音声 also becomes a nasal vowel. But I clearly hear [onse:] [kansha] instead of [oĩse:] [kaĩsha]
I have listened audios from different people and I always hear the same thing. In theory the word 先生 is also pronounced [seĩse:] but I always hear [sense:]
I don't know if my ears can't hear nasal vowels in these cases, and Japanese can clearly hear the difference.
Video is wrong and 音声, 感謝,先生 are pronounced [onse:]; [kansha]; [sense:] ?
Thank you very much for the help