Frequency and wavelength

As in Chapter 4.1, the decomposition of waves into frequency components becomes important. For sound, the frequency is the number of compressions per second and is called pitch. The range is generally considered to be from $20$ Hz to 20,000 Hz, which is based on human hearing, much in the same way that the frequency range for light is based on human vision. Vibrations above 20,000 Hz are called ultrasound, and are audible to some animals. Vibrations below $20$ Hz are called infrasound.

Using (4.1) from Section 4.1 and the propagation speed $s = 343.2$, the wavelength of a sound wave can also be determined. At $20$ Hz the wavelength is $\lambda = 343.2 / 20 = 17.1$m. At 20,000 Hz, it becomes $\lambda = 17.1$mm. The waves are the sizes of objects in our world. This causes the sound to interfere with objects in a complicated way that is difficult to model when trying to reproduce the behavior in VR. By comparison, light waves are tiny, ranging from $400$ nm to $700$ nm.