Final answer:
The critical frequency affects signal propagation and reception characteristics like channel width and signal strength but does not have perceivable 'sounds' or 'colors'. In sound waves, it relates indirectly to pitch, where a person can generally distinguish a 0.3% difference between two frequencies.
Step-by-step explanation:
The critical frequency of a signal, particularly in the context of radio communications or sound waves, is important because it helps determine the signal's range and clarity. The critical frequency itself does not have a 'sound' or 'color,' but it has perceivable characteristics in its effects on how a signal propagates or is received. For example, it can affect how wide in frequency the communication channel is, the strength of a signal received by radio telescopes, and whether a signal is continuous or intermittent.
Regarding the perception of frequency as pitch in sound waves, most people can discriminate between two sounds if their frequencies differ by 0.3% or more. In contrast, the average person may struggle to discern differences between sounds with very close frequencies, such as 1999 Hz and 2002 Hz, unless played simultaneously.
Factors like the Doppler effect can cause a signal to drift (change) in frequency due to the changing relative motion between the source and the receiver, which might result in perceivable changes in pitch when it comes to sound waves.