Here's how:

* Wavelength: The distance between two successive crests (or troughs) of a wave. It's usually measured in meters (m).

* Frequency: The number of waves passing a fixed point in one second. It's usually measured in Hertz (Hz), where 1 Hz represents one wave per second.

The relationship between these three is:

Speed (v) = Wavelength (λ) x Frequency (f)

So, to measure the speed of a wave, you need to know its wavelength and frequency.