The phonology of Welsh is characterised by a number of sounds that do not occur in English and are rare in European languages, such as the voiceless alveolar lateral fricative [ɬ] and several voiceless sonorants (nasals and liquids), some of which result from consonant mutation. Stress usually falls on the penultimate syllable in polysyllabic words, while the word-final unstressed syllable receives a higher pitch than the stressed syllable.