冷峻科幻确认音

Low sci-fi ominous confirmation, 600 ms. A single 100 Hz struck steel tone with a slow 300 ms swell and a thin high 2.2 kHz tension layer on top, fading cleanly. Feels like a countdown starting. Cold, mechanical, slightly tense. Dry, no reverb, no musical chord, no cinematic swell. Sustain the full stated duration.