33 C.F.R. § 86.03 Limits of fundamental frequencies.
Title 33 - Navigation and Navigable Waters
To ensure a wide variety of whistle characteristics, the fundamental frequency of a whistle shall be between the following limits: (a) 70–200 Hz, for a vessel 200 meters or more in length; (b) 130–350 Hz, for a vessel 75 meters but less than 200 meters in length; (c) 250–525 Hz, for a vessel less than 75 meters in length.
Title 33: Navigation and Navigable Waters
PART 86—ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES
Subpart A—Whistles
§ 86.03 Limits of fundamental frequencies.
