As we saw in part 1, sound is made up of waves of compressions and rarefactions in the air molecules around us. In part 2 we are going to talk about 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, frequencies are measured in Hertz (Hz) and a human can hear from around 20 Hz to around 20,000 Hz (or 20kHz). Though this would be someone with very good hearing and these values vary from person to person and they also vary with age. But what does this really mean.

If a sound has a frequency of 1 Hertz it means that there was one cycle (wavelength) in one second. We can hear sounds which are 20 wavelengths per second to 20,000 wavelengths per second. We perceive these wavelengths as frequencies. if we hear a sound at say 60Hz we will hear this as a very low sound, where as if we hear a sound which is say at 10kHz we will hear this as a high sound. Our ears though are not sensitive to all those frequencies by the same amount though. We are less senstive to the sounds at the extremes of our hearing. We are much more sensitive to the sound from a range of approximately 100Hz to 3000Hz. This range is funnily enough where the main frequencies of the normal human voice are.

Article written by Edward Cufaude for Rhythm Creation