As we saw in part 1, sound is made up of waves of compressions and rarefactions in the air molecules around us. In this post we are going to look at frequency and wavelength and how they relate to these compressions and rarefactions and how they relate to each other. I think it is important to understand these when creating music with a computer. Understanding frequencies can really help with your mixdowns and EQing.

Wavelength
In a sound we get compressions and rarefactions in the air molecules, when we look at these in a waveform editor we see a wave. In the picture below we can see a waveform of a sine wave. Wavelength is very easy to understand as it is the distance between any two points at the exact same point in the cycle of the wave. The arrows in the image below show the wavelength and points in which you can measure it.


These points in effect relate to the the distance (the wavelength) between these compressions and rarefactions in the air molecules of the sound wave travelling through the air.

Relating Wavelength to Frequency
Human ears can hear a range of different frequencies which can be measured in Hertz (Hz) and a human has a hearing range from around 20 Hz to around 20,000 Hz (or 20kHz). This would be someone with very good hearing and these values vary from person to person and they also vary with age.

If a sound has a frequency of 1 Hertz it means that there was one cycle (wavelength) in one second. Low sounds are lower in the number of wavelength, so 60Hz would be a bass sound. High sounds such as those at say at 10kHz will sound high like a whistle. The human voice typically is between 100Hz and 3kHz.

Our ears are not sensitive to each frequency in equal measures. We are much less sensitive to the sounds at the extremes of our hearing. The range where humans excel at hearing ability is approximately 100Hz to 3kHz. This range is funnily enough where the main frequencies of the normal human voice are.

Article written by Edward Cufaude for Rhythm Creation.