Dual-tone Siren Rotor Vane Ratios and Musical Intervals
| Rotor Ratio | Musical Interval | Examples |
| 2/1 | Octave | Sentry 10v2T, 15v2T, 20v2T and Sterling M series dual-tones (16/8) |
| 3/2 | 5th | ACA Cyclone (12/8), Sentry 40v2T (15/10) |
| 4/3 | 4th | Model 5T, SD-10, Allertor (all 12/9) |
| 5/4 | Major 3rd | Dual-tone Model 2 (5/4) |
| 6/5 | Minor 3rd | 2T22/3T22 and WWII Carters (12/10) Thunderbolt 1000T/1003 (6/5) |
| 9/8 | Whole Step (2nd) | Federal 76, 77, 78 fire engine sirens (all 9/8) |
Siren Pitch as a Function of
Motor RPM and Rotor Vane Count
| Motor R.P.M. | Rotor Vane Count | |||||||
| 4 | 5 | 6 | 8 | 9 | 10 | 12 | 16 | |
| 3450 60Hz, 2-pole Induction† |
460 | 518 | 575 | 690 | 920 | |||
| 2850 50Hz, 2-pole Induction |
380 | 428 | 475 | 570 | ||||
| 6396 Model 2 & Tbolt Chopper @ 220V |
425 | 533 | 640 | |||||
| 6960 Model 2 & Tbolt Chopper @ 240V |
464 | 580 | 696 | |||||
†Note that 3450 RPM is typical slip for a lightly loaded motor. Heavily loaded siren motors actually have a lot more slip, with final RPMs usually between 3300 and 3400 RPM.