Wikipedia
In Swedish phonology, the sj-sound is a voiceless fricative phoneme found in most dialects. It has a variety of realisations, whose precise phonetic characterisation is a matter of debate, but which usually feature distinct labialization. The sound is represented in Swedish orthography by a number of spellings, including the digraph from which the common Swedish name is derived as well as , , and before front vowels. The sound should not be confused with the Swedish tj sound , often spelled tj or k in Swedish.
The sound is transcribed in the International Phonetic Alphabet. The International Phonetic Association (IPA) describes as a "simultaneous and ", but this claim is disputed among phoneticians, including at least one former president of the IPA. Other descriptive labels include voiceless postalveolo-velar fricative, voiceless palatal-velar fricative, voiceless dorso-palatal velar fricative, voiceless postalveolar and velar fricative, or voiceless coarticulated velar and palatoalveolar fricative.