You may have wondered how we came up with the recommendation that women have 500 calories and men have 600 calories on a Fast Day. We used the rule of thumb that women need 2000 calories and men need 2400 calories per day and on a Fast Day you should eat a quarter of a normal dayâs recommended calories. Some of you have also wondered exactly how many calories you should be eating on days when youâre not fasting.
According to most sources, the human hearing (frequency) range is between 20 Hz and 20,000 Hz (bats can hear up to 100,000 Hz!). What does that mean? Sound is a mechanical wave that propagates through a medium (air, water), and the frequency of a sound wave determines its tone and pitch.
There are still plenty of sounds in the world that you canât detect. The low range of human hearing starts around 20 hertz, and tops out at about 20,000 [PDF]. By contrast, bats can hear ultrasonic sounds with frequencies up to 110,000 hertz. Other animals, like elephants, hear sounds many times lower than those a human can perceive. And as people age, their hearing gets even worse, eliminating even more sounds from the range of audible noises. Here are just a few sounds most people are missing out on: