The integration is about the calculation of areas.
ð ɪ WORD_BOUNDARY ɪ n t ɪ ɡ ɹ eɪ ʃ ə n WORD_BOUNDARY ɪ z WORD_BOUNDARY ʌ b aʊ t WORD_BOUNDARY ð ə WORD_BOUNDARY k æ l k j ʊ l eɪ ʃ ə n WORD_BOUNDARY ʌ v WORD_BOUNDARY ɛ ɹ iə z WORD_BOUNDARY