6. middle a on a piano is known as a4.its sound wave has a frequency of 440 cycles per sound, also written as 440 hertz (hz).the table shows the frequencies of each of the eight a-notes on a piano. 01 2 3 4 5 6 7 a-note frequency(hz) 27.5 55 110 220 440 880 1760 3520 show that the relationship between the a-notes on a piano and their f be modeled using exponential growth. requencies can (5k/u)