Why Can't A Name Be Written Literally In Japanese?


My Japanese knowledge is very limited, so I am not good in Japanese alphabet.  
With the help of an online [Japanese name
converter](https://apps.nolanlawson.com/japanese-name-converter), I tried
writing a name in Japanese, but the resulting name does not sound exactly as
it is in English. It seems some characters turn into other characters.

The name is: Siavash Divani The result is: シアバシュ ディバニ (shiabashu dibani)

As you see in the parentheses, it sounds different from the English spelling.
Is it possible to write the name in Japanese in a way that sounds just the way
it is written in English? If the answer is no, why?
[Wikipedia](https://en.wikipedia.org/wiki/Japanese_writing_system) says that
only the kanji system has over 50,000 characters. So, it seems it should
support writing foreign names in a way that sounds the way you like.




**Basically, there are just some sounds that exist in other languages which
cannot easily be phonemically represented in Japanese.**

Disclaimer - this is a simplified answer, but ...

As with any language, you must differentiate between the actual sounds
(phonology) and the writing system which represents the language
(orthography). Although there are several thousand kanji characters which form
the basis of the writing system (2136 on the official list), that doesn't mean
there are 2136 individual sounds. In fact, there are approximately 50 sounds
in Japanese (or around 100 if you include dakuon and yoon). By 'sounds', I
mean the variations of vowel and consonant combinations which are used in
spoken Japanese.

That is probably a lot less than you imagined. As such, there are some sounds
that exist in other languages which are not easily transferred to Japanese.
They simply are not part of the standard collection of sounds in Japanese
phonology. A famous example is that there is no strict equivalent of 'l' and
'r' in Japanese - the ら、り、る、れ、ろ sounds are used to represent both. So if your
name was 'Roland', it would be difficult to represent the difference between
the 'r' and 'l' sounds. It would be ローランド, which when pronounced would not
contain the distinction that you would hear if pronounced in English, for
example.

