Evading enemies is the name of the game in Metal Gear Solid Delta: Snake Eater but this can be exceptionally difficult given the detection abilities of the NPC AI. Once detected however, Snake can tune in to these secret frequencies to cancel the alert phase entirely.
This Metal Gear Solid Delta: Snake Eater guide lists every single Cancel Alert frequency for each of the various difficulty levels.
Very Easy & Easy
- 143.03: Bolshaya Past South
- 149.75: Ponizovje Warehouse: Exterior
- 149.63: Ponizovje Warehouse
- 149.90: Graniny Gorki Lab 1F/2F
- 148.87: Svyatogornyj West
- 146.59: Svyatogornyj East
- 145.94: Krasnogorje Mountainside
- 140.15: Krasnogorje Mountaintop
- 143.16: Groznyj Grad 1F Southwest Section
- 147.49: Groznyj Grad 1F Northwest Section
- 143.94: Groznyj Grad Weapons Lab East Wing
Normal
- 147.11: Bolshaya Past South
- 149.46: Bolshaya Past Base
- 140.61: Ponizovje West
- 141.45: Ponizovje Warehouse
- 142.79: Svyatogornyj West
- 148.04: Svyatogornyj East
- 146.67: Krasnogorje Mountainside
- 141.98 Krasnogorje Mountaintop
- 141.53: Groznyj Grad 1F Northeast Section
- 144.40: Groznyj Grad 1F Southeast Section
- 144.61: Groznyj Grad Weapons Lab East Wing
Hard
- 146.20: Dolinovodno
- 146.91: Bolshaya Past South
- 145.42: Ponizovje West
- 142.48: Ponizovje Warehouse
- 144.87: Graniny Gorki Lab B1 East
- 145.59: Svyatogornyj West
- 142.03: Svyatogornyj East
- 140.94: Krasnogorje Mountain Base
- 140.58: Krasnogorje Mountaintop
- 147.54: Groznyj Grad 1F Southwest Section
- 146.08: Groznyj Grad 1F Southeast Section
- 147.65: Groznyj Grad Weapons Lab East Wing
Extreme
- 142.65: Dolinovodno
- 144.52: Bolshaya Past South
- 143.72: Ponizovje Warehouse
- 145.07: Graniny Gorki Lab 1F/2F
- 145.31: Graniny Gorki Lab B1 East
- 144.28: Svyatogornyj West
- 147.79: Svyatogornyj East
- 148.54: Krasnogorje Mountain Base
- 148.26: Krasnogorje Mountaintop
- 140.47: Groznyj Grad 1F Northwest Section
- 141.17: Groznyj Grad 1F Northeast Section
- 144.14: Groznyj Grad Weapons Lab East Wing
Note that despite knowing the frequency and it remaining exactly the same, you must perform an interrogation that yields the frequency each time in order to successfully cancel the alert phase. This peculiarity even applies if you leave the area and come right back. The frequencies cannot be used pre-emptively either, so the alert phase must be active in the first place.
Those are all of the secret Cancel Alert frequencies for every difficulty setting in Metal Gear Solid Delta: Snake Eater.