# Grandma Moon Speaks: Frequency Range of the Human Ear

Topics Covered:

• Audible Range of the Human Ear
• Audio or Sonic Range
• Ultrasonic and Infrasonic Frequencies

I remember attaching a wire clothing hanger to the antenna of my radio in my bedroom, so I could get the frequency and get that station and listen to the top 10 every night – Nelly Furtado

The average human is capable of hearing frequencies between 20 Hz and 20,000 Hz (20 KHz). This range is called the audio or sonic range.

Frequencies higher than 20 Khz are called ultrasonic, while frequencies below 20 Hz are infrasonic. Some animals are capable of hearing outside the audio range. E.g., bats and dogs are capable of perceiving ultrasonic frequencies, while snakes, whales, dolphins and elephants, etc use infrasonic frequencies.

If you’ve read Professor Sampler’s notes regarding the Nyquist Theorem, you’ll know that it requires a sampling frequency of at least twice the maximum frequency of a signal.

In this case, since the audio range has a maximum frequency of 20 KHz, the typical sampling frequency should be above 40 KHz. This is why the base frequency of broadcast audio, CDs and DVDs, etc., are set to 44.1 KHz, which is slightly above this number.

Since film runs at 24 fps, the most widely available standard for audio sampling is 48 KHz, which is easier to sync with the image at 24 fps. This does not mean that one is limited to this frequency. As Sampler might have told you, the higher your sampling frequency the better the end result of digitization. Many professional-level systems can sample at 192 KHz or more.

Takeaways:

• The human range of frequencies, called the audio or sonic range, is limited to between 20 Hz and 20,000 Hz.
• Frequencies above 20 KHz are called ultrasonic and frequencies below 20 Hz are called infrasonic.
• The typical broadcast standard for audio is set to 44.1 Hz because it is the Nyquist sampling frequency that encompasses the sonic range.