I've seen many questions asked about the ん sound, both on this site and others, but I'm still uncertain about how it should be produced before a fricative (e.g. さ, し, ひ, ふ). So I'm hoping someone can give a good, thorough answer if I ask about it specifically.
Different sources seem to give different pronunciations. Some sources say it is similar to the English n or ng sound, but with the same place of articulation as the following sound. So if it is followed by s it would be a lamino-alveolar nasal. Some sources say it is like a nasalized う. Other sources simply say it is a nasalized vowel.
So is one of these correct and the others incorrect. Are none of them correct. Or does it vary by speaker. If it varies, is any pronunciation commonly regarded as standard and/or more neutral. The opinions of native speakers or those familiar with Japanese linguistics would be especially appreciated.