The spelling of the word "Karlssen" can be explained through its International Phonetic Alphabet (IPA) phonetic transcription. The word is pronounced as /ˈkɑːlsən/, which signifies that it has two syllables, starting with the stressed "KAHL" sound, followed by an unstressed "sən" sound. The first sound is pronounced with an open back vowel "ɑː", followed by a centrally pronounced "l" sound, and an unvoiced "s" sound. The last syllable ends with a weak "ən" sound pronounced with a nasal vowel.