record time for echo to be heard then use speed = distance/time
have two mics connected to a cataloger at a larger distance apart, and record the time difference between a sound passing one to the other - then use speed = distance/time
Ripples on water surface:
Use a stroboscope, which has the same frequency as the water waves, then measure distance between the 'fixed' ripples and use velocity = frequency x wavelength
Or move a pencil along the paper at the same speed as a wavefront, and measure the time taken to draw this line, then use speed = distance/time
