Low frequency pulsing and humming signal:
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Welcome, Morse code
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Horrifying throbbing low-frequency rumble
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Low frequency pulsing and humming signal
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Brown noise
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Low frequency electronic signal
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High frequency pulsating electronic signal
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High frequency signal
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Radio noise
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High frequency squeak
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High-frequency squeak, Low-frequency rumble
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SOS signal transmission, Morse code
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Morse code, reception, transfer
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