33 C.F.R. § 86.15 Towing vessel whistles.
Title 33 - Navigation and Navigable Waters
A power-driven vessel normally engaged in pushing ahead or towing alongside may, at all times, use a whistle whose characteristic falls within the limits prescribed by §86.03 for the longest customary composite length of the vessel and its tow.
Title 33: Navigation and Navigable Waters
PART 86—ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES
Subpart A—Whistles
§ 86.15 Towing vessel whistles.
