Low frequency electronic signal:
-
Brown noise
-
Low frequency electronic signal
-
Morse code, welcome
-
SOS signal transmission, Morse code
-
Morse code, SOS signal reception
-
Horrifying throbbing low-frequency rumble
-
Morse code transmission
-
Police radio
-
Geiger counter
-
High frequency pulsating electronic signal
-
High frequency squeak
-
High-frequency squeak, Low-frequency rumble
★★★★★