Human ears are good at hearing low pitches, but bad at hearing high pitches. If you use the DCT to break a sound into tones, you do not need to be as careful when playing the higher tones because people cannot hear them as well. MP3 encoders (programs which make MP3s) use this fact to make the sound smaller.
h j uː m ə n WORD_BOUNDARY ɪ ɹ z WORD_BOUNDARY ɑ ɹ WORD_BOUNDARY ɡ ʊ d WORD_BOUNDARY æ t WORD_BOUNDARY h ɪ ɹ ɪ ŋ WORD_BOUNDARY l oʊ WORD_BOUNDARY p ɪ t̠ʃ ɪ z WORD_BOUNDARY b ʌ t WORD_BOUNDARY b æ d WORD_BOUNDARY æ t WORD_BOUNDARY h ɪ ɹ ɪ ŋ WORD_BOUNDARY h aɪ WORD_BOUNDARY p ɪ t̠ʃ ɪ z WORD_BOUNDARY ɪ f WORD_BOUNDARY j uː WORD_BOUNDARY j uː z WORD_BOUNDARY ð ə WORD_BOUNDARY d iː s iː t iː WORD_BOUNDARY t ə WORD_BOUNDARY b ɹ eɪ k WORD_BOUNDARY ʌ WORD_BOUNDARY s aʊ n d WORD_BOUNDARY ɪ n t ʊ WORD_BOUNDARY t oʊ n z WORD_BOUNDARY j uː WORD_BOUNDARY d uː n ɑ t WORD_BOUNDARY n iː d WORD_BOUNDARY t ə b i WORD_BOUNDARY æ z WORD_BOUNDARY k ɛ ɹ f ə l WORD_BOUNDARY w ɛ n WORD_BOUNDARY p l eɪ ɪ ŋ WORD_BOUNDARY ð ə WORD_BOUNDARY h aɪ ə ɹ WORD_BOUNDARY t oʊ n z WORD_BOUNDARY b ɪ k ʌ z WORD_BOUNDARY p iː p ə l WORD_BOUNDARY k æ n ɑ t WORD_BOUNDARY h ɪ ɹ WORD_BOUNDARY ð ɛ m WORD_BOUNDARY æ z WORD_BOUNDARY w ɛ l WORD_BOUNDARY ɛ m p iː WORD_BOUNDARY θ ɹ iː WORD_BOUNDARY ɛ ŋ k oʊ d ə ɹ z WORD_BOUNDARY p ɹ oʊ ɡ ɹ æ m z WORD_BOUNDARY w ɪ t̠ʃ WORD_BOUNDARY m eɪ k WORD_BOUNDARY ɛ m p iː WORD_BOUNDARY θ ɹ iː WORD_BOUNDARY z WORD_BOUNDARY j uː s WORD_BOUNDARY ð ɪ s WORD_BOUNDARY f æ k t WORD_BOUNDARY t ə WORD_BOUNDARY m eɪ k WORD_BOUNDARY ð ə WORD_BOUNDARY s aʊ n d WORD_BOUNDARY s m ɔ l ə ɹ WORD_BOUNDARY