| CPC B60Q 1/346 (2013.01) [B60Q 1/2611 (2013.01)] | 20 Claims |

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1. A siren, comprising:
a motor;
a stator;
a rotor configured to be driven by the motor to spin relative to the stator, a spin speed of the rotor determining an attribute of a siren sound produced by the siren; and
a controller including a processor and memory, the memory encoding instructions which, when executed by the processor, cause the controller to modify the attribute of the siren sound by adjusting the spin speed.
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