Introduction: Moving sources emitting spiral waves (SSp) such as cardiac rotors, do not exhibit frequency changes typical of classic Doppler effect (CDE) physics. Rotors exhibited fastest and slowest frequencies at either side when migrating passed electrodes, not directly in front and behind as in CDE. A new spiral wave frequency effect (SFE) equation required derivation to accurately describe and predict WF frequency changes observed near a moving SSp. Methods and Results: Rotational and spiral math were developed to derive new rotational wave frequency effect (RFE) and SFE equations in two dimensions. Wave front (WF) strikes from SR occur when clock angle equaled the line of sight (LOS) angle. WF strikes from spiral sources occurred when spiral summation angle equaled LOS angle. SFE is analyzed by varying spiral size and distance from SSp. New RFE and SFE equations predict diametric changes in frequency that occur simultaneously on either side of a passing rotor. Conclusions: WF frequency changes near a moving SSp exhibit 3 main differences compared to CDE: side-dependent frequency changes, a strong-side unpaired WF strike, and a reversal of sequence of activation. These differences, predicted by new RFE and SFE equations, constitute the unique diametric property of the rotating waves. Moving bodies that spin, or moving sources of WFs that rotate, result in perceived frequency differences that are relative to side of observation. Additionally, increasing and decreasing frequencies observed, no longer always represent an approaching and receding SR and SSp (respectively), especially when observed near the source.