Correct pronunciation of voiceless bilabial fricative [ɸ]


I found that there are two different pronunciations for the [ɸ] phone. For
example, in Japanese compare those two pronunciations for same word 冬 (for
which I believe will has [ɸɯjɯ] as **phonetic** transcription):

  * <https://jisho.org/search/%E5%86%AC>. To my ear, this one sounds more like [pʰɯjɯ].
  * [https://translate.google.com/#view=home&op=translate&sl=ja&tl=en&text=fuyu](https://translate.google.com/#view=home&op=translate&sl=ja&tl=en&text=fuyu). . To my ear, this one sounds more like [kʰɯjɯ].

In [this wikipedia
page](https://en.wikipedia.org/wiki/Voiceless_bilabial_fricative), which
provides the audio sample for the sound (near the top right of the page), I
also found that phone is pronounced much similar to the first link in the list
above.

However, some other sources suggest that the pronunciation link in second link
is also common. For example, this link:
<http://www.guidetojapanese.org/learn/grammar/hiragana> provides pronunciation
for /hu/.

So which one is correct, or both?

**Note** : I'm a Vietnamese native speaker and in our country, almost anyone
can spot the difference between the two pronunciations in the links listed
above.




It turns out that OP's question is that Japanese ふ sometimes sounds as if
Vietnamese _ph_ //f// and other times _kh_ //x//.

That observation is true. The status of [[ɸ]] sound in Japanese is somewhat
shaky because it appears mostly as [an allophone in the environment //h// +
//u//](https://japanese.stackexchange.com/q/16266/7810) (strictly speaking,
however, influx of modern loanwords has developed independent ファ行 to a quite
degree).

[[ɸ]] in the Japanese language is a historical remnant of the times when all
ハ行 were //ɸ//, which now only retained because //u// has labial feature.
Hence, to some speakers the labiality is essential in pronunciation, while to
others it is merely incidentally labialized //h//. In other words, the
strength of labial narrowing varies among speakers.

Another factor is the realization of //h//. It is pronounced not only as [[h]]
but also as [[x]] or [[χ]], especially in Eastern Japan including Tokyo. (Note
that these allophones are natural in most regions when after consonantal
element, cf. [ゴッホ](https://forvo.com/word/%E3%82%B4%E3%83%83%E3%83%9B/#ja).)
Since we don't have any contrastive fricatives in the back side of cavity,
//h// can be freely realized from [[h]] (≈ Vietnamese _h_ ) to [[x]] (≈
Vietnamese _kh_ ).

Then we can draw a diagram to illustrate the gradation of ふ's consonant:

[code]

    strong labial                      [ɸ]
         ↕
     weak labial           [hʷ]                    [xʷ]
                          glottal <--------------> velar
    
[/code]

For example, in [the sound clips of 船（ふね） on
forvo.com](https://forvo.com/word/%E8%88%B9/#ja), _strawberrybrown_ 's is
closest to [[ɸ]], _akitomo_ 's closest to [[hʷ]], and _kaoring_ 's closest to
[[xʷ]] (I couldn't get each direct link).

I'm not sure what is the distinctive features of _ph_ in Vietnamese, but your
first link of 冬 from jisho.org sounds rather an example of [[hʷ]] (though it
doesn't seem to be a human articulation).

**PS** As an aside, it reminds me of [a female announcement voice for some JR
lines](https://youtu.be/XRr7IF0Qy54?t=28) which utters ふつう with such
strikingly dominant velar feature that almost sounds like くつう to me.




It turns out that OP's question is that Japanese ふ sometimes sounds as if
Vietnamese _ph_ //f// and other times _kh_ //x//.

That observation is true. The status of [[ɸ]] sound in Japanese is somewhat
shaky because it appears mostly as [an allophone in the environment //h// +
//u//](https://japanese.stackexchange.com/q/16266/7810) (strictly speaking,
however, influx of modern loanwords has developed independent ファ行 to a quite
degree).

[[ɸ]] in the Japanese language is a historical remnant of the times when all
ハ行 were //ɸ//, which now only retained because //u// has labial feature.
Hence, to some speakers the labiality is essential in pronunciation, while to
others it is merely incidentally labialized //h//. In other words, the
strength of labial narrowing varies among speakers.

Another factor is the realization of //h//. It is pronounced not only as [[h]]
but also as [[x]] or [[χ]], especially in Eastern Japan including Tokyo. (Note
that these allophones are natural in most regions when after consonantal
element, cf. [ゴッホ](https://forvo.com/word/%E3%82%B4%E3%83%83%E3%83%9B/#ja).)
Since we don't have any contrastive fricatives in the back side of cavity,
//h// can be freely realized from [[h]] (≈ Vietnamese _h_ ) to [[x]] (≈
Vietnamese _kh_ ).

Then we can draw a diagram to illustrate the gradation of ふ's consonant:

[code]

    strong labial                      [ɸ]
         ↕
     weak labial           [hʷ]                    [xʷ]
                          glottal <--------------> velar
    
[/code]

For example, in [the sound clips of 船（ふね） on
forvo.com](https://forvo.com/word/%E8%88%B9/#ja), _strawberrybrown_ 's is
closest to [[ɸ]], _akitomo_ 's closest to [[hʷ]], and _kaoring_ 's closest to
[[xʷ]] (I couldn't get each direct link).

I'm not sure what is the distinctive features of _ph_ in Vietnamese, but your
first link of 冬 from jisho.org sounds rather an example of [[hʷ]] (though it
doesn't seem to be a human articulation).

**PS** As an aside, it reminds me of [a female announcement voice for some JR
lines](https://youtu.be/XRr7IF0Qy54?t=28) which utters ふつう with such
strikingly dominant velar feature that almost sounds like くつう to me.

