Simplify the following text for a Grade 8 native English-speaking person.
Original: The human ear can recognize single sine waves as sounding clear because sine waves are representations of a single frequency with no harmonics ; some sounds that approximate a pure sine wave are whistling , a crystal glass set to vibrate by running a wet finger around its rim , and the sound made by a tuning fork .
Simplified: Sine waves have a `` length '' called a wavelength . There are other properties of waves and sine waves , such as their frequency , amplitude , phase , and speed .