The audio starts with a low, ominous hum, resembling a siren, which gradually gains volume. This isn't your typical high-pitched, sharp alarm sound. Instead, this siren is deep, resonating, and persistent, echoing an air-raid alarm. The intensity of the sound waxes and wanes, creating a chilling effect that sends shivers down your spine. It's a quintessential sound effect that immediately grabs your attention, transporting you to a scene of an impending air-raid in a war film or a suspense thriller. The low-pitched siren sound continues to reverberate, creating a sense of urgency and impending danger, before it slowly fades out.