Texas Transportation Code - TRANSP § 547.501. Audible Warning Devices

(a) A motor vehicle shall be equipped with a horn in good working condition that emits a sound audible under normal conditions at a distance of at least 200 feet.

(b) A vehicle may not be equipped with and a person may not use on a vehicle a siren, whistle, or bell unless the vehicle is:

(c) A motor vehicle operator shall use a horn to provide audible warning only when necessary to insure safe operation.

(d) A warning device, including a horn, may not emit an unreasonably loud or harsh sound or a whistle.