The intensity of an electromagnetic wave is only related to its amplitude (E^2) and not its frequency. A photon has the same wavelength as the wave that's carrying it, and its energy is h x f. 

So if a laser wave is kept at the same amplitude and the frequency is reduced, why does its intensity remain the same even though its photons now carry more energy?

Why are the intensities of electromagnetic waves so different to sound waves (and other waves travelling through a medium) which are related to f^2 X E^2?