工业警告双脉冲

Ominous industrial warning tone, 900 ms. Two low metallic pulses 400 ms apart, each a 150 Hz struck steel bar with a detuned second layer a few cents flat, and a thin high 2.5 kHz tension hiss riding underneath. Feels like a hardened facility alarm cycling up, cold and mechanical. Dry and close, no reverb, no siren sweep, no orchestral brass, no horror sting.