Horrifying throbbing low-frequency rumble:
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Morse code, SOS signal reception
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Radio noise
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White noise
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Reception, transfer, Morse code
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Police radio
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Morse code, SOS signal transmission
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Morse code transmission
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High frequency signal
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High-frequency squeak, Low-frequency rumble
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Interference Broadcasting
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Electronic signal
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High frequency pulsating electronic signal
★★★★★