The result of this exercise depends largely on how accurate your IPA transcription is, because that is very much a scale. More often than not, what you see is a

The result of this exercise depends largely on how accurate your IPA transcription is, because that is very much a scale. More often than not, what you see is a phonemic transcription rather than a phonetic one, which then does indeed require knowing how the actual phonemes are pronounced in a particular language. But with phonemic translation using the entire assortment of IPA diacritics, if your linguist is familiar with other languages that happen to have the same sounds, they could do a fairly decent take.