ɪn pɚtˈɪkjʊlɚ, ɪf wiː ˈæd ˈɛn slˈæʃ fˈoːɹ tə kˈeɪ, ðə sˈaɪzˈɛn slˈæʃ fˈoːɹ dˌiːˌɛftˈiːz ɑːɹ nˌɑːt tʃˈeɪndʒd bɪkˈʌz ðeɪ ɑːɹ pˌiəɹɪˈɑːdɪk ɪn ˈɛn slˈæʃ fˈoːɹ, wˌaɪl ðə sˈaɪzˈɛn slˈæʃ tˈuː dˌiːˌɛftˈiː ɪz ʌntʃˈeɪndʒd ɪf wiː ˈæd ˈɛn slˈæʃ tˈuː tə kˈeɪ.
In particular, if we add N/4 to k, the size-N/4 DFTs are not changed (because they are periodic in N/4), while the size-N/2 DFT is unchanged if we add N/2 to k.