At a recent checkup, I was shocked: Even though I was eating foods rich in saturated fat and a seemingly more indulgent diet, my total cholesterol was down 10 points, my bad LDL cholesterol was stellar, and my good HDL was the highest it's ever been.
As the frequency of the signal to be measured increases to approach the frequency of the source frequency, measurement error increases. To improve the accuracy of the frequency measurement for higher unknown frequency, we can use this second measurement method, count number of pulses in known time.
Frequency is measured using the Hz symbol meaning Hertz. The chart above shows a total span of frequencies from 20 Hz to 130,000 Hz. Noting that the limitation of the range of human hearing is between 20 Hz and 20,000 Hz one can easily see that frequencies exist outside of our capability to hear them.