NRS 484D.400
Horns and other warning devices.
1.
Every motor vehicle when operated upon a highway must be equipped with a horn in good working order and capable of emitting sound audible under normal conditions from a distance of not less than 200 feet, but the horn or other warning device must not emit an unreasonably loud or harsh sound or a whistle.2.
A person driving a motor vehicle shall, when reasonably necessary to ensure safe operation, give audible warning with the horn, but shall not otherwise use the horn when upon a highway.3.
A vehicle must not be equipped with, and a person shall not use upon a vehicle, a siren, whistle or bell, except as otherwise provided in this chapter.4.
It is permissible, but not required, to equip a vehicle with a theft alarm which is arranged so that it cannot be used by the driver as an ordinary warning signal.5.
An authorized emergency vehicle may be equipped with a siren, whistle or bell, capable of emitting sound audible under normal conditions from a distance of not less than 500 feet, but the siren must not be used except when the vehicle is operated in response to an emergency call or in the immediate pursuit of an actual or suspected violator of the law, in which event the driver of the vehicle may sound the siren to warn pedestrians and other drivers of his or her approach. A driver of an emergency vehicle may operate the vehicle’s warning lamps without sounding the siren.6.
A driver of an emergency vehicle who operates the vehicle’s warning lamps without sounding the siren shall be deemed to have adequately warned pedestrians and other drivers of his or her approach for the purpose of determining whether the driver met the duty to drive with due regard for the safety of all persons pursuant to NRS 484B.700.
Source:
Section 484D.400 — Horns and other warning devices., https://www.leg.state.nv.us/NRS/NRS-484D.html#NRS484DSec400.