For sounds, frequencies are the same as simple tones. You can make any sound by playing several tones at the same time. The discrete cosine transform is a way to find out which tones to play in order to make a given sound. The only difference between the tones is their pitch.
f ɔ ɹ WORD_BOUNDARY s aʊ n d z WORD_BOUNDARY f ɹ iː k w ə n s i z WORD_BOUNDARY ɑ ɹ WORD_BOUNDARY ð ə WORD_BOUNDARY s eɪ m WORD_BOUNDARY æ z WORD_BOUNDARY s ɪ m p ə l WORD_BOUNDARY t oʊ n z WORD_BOUNDARY j uː WORD_BOUNDARY k æ n WORD_BOUNDARY m eɪ k WORD_BOUNDARY ɛ n i WORD_BOUNDARY s aʊ n d WORD_BOUNDARY b aɪ WORD_BOUNDARY p l eɪ ɪ ŋ WORD_BOUNDARY s ɛ v ɹ ə l WORD_BOUNDARY t oʊ n z WORD_BOUNDARY æ t WORD_BOUNDARY ð ə WORD_BOUNDARY s eɪ m WORD_BOUNDARY t aɪ m WORD_BOUNDARY ð ə WORD_BOUNDARY d ɪ s k ɹ iː t WORD_BOUNDARY k oʊ s aɪ n WORD_BOUNDARY t ɹ æ n s f ɔ ɹ m WORD_BOUNDARY ɪ z WORD_BOUNDARY ʌ WORD_BOUNDARY w eɪ WORD_BOUNDARY t ə WORD_BOUNDARY f aɪ n d WORD_BOUNDARY aʊ t WORD_BOUNDARY w ɪ t̠ʃ WORD_BOUNDARY t oʊ n z WORD_BOUNDARY t ə WORD_BOUNDARY p l eɪ WORD_BOUNDARY ɪ n WORD_BOUNDARY ɔ ɹ d ə ɹ WORD_BOUNDARY t ə WORD_BOUNDARY m eɪ k WORD_BOUNDARY ʌ WORD_BOUNDARY ɡ ɪ v ə n WORD_BOUNDARY s aʊ n d WORD_BOUNDARY ð ɪ WORD_BOUNDARY oʊ n l i WORD_BOUNDARY d ɪ f ɹ ə n s WORD_BOUNDARY b ɪ t w iː n WORD_BOUNDARY ð ə WORD_BOUNDARY t oʊ n z WORD_BOUNDARY ɪ z WORD_BOUNDARY ð ɛ ɹ WORD_BOUNDARY p ɪ t̠ʃ WORD_BOUNDARY