Cunningham Air Whistles Over 70 years of service have marked the Cunningham Air Whistle a leader in marine and industrial fields. There are three features of the Cunningham Whistle which are outstanding: Clarity of tone, due to the unobstructed passageway for the sound Steady pitch, regardless of changing air pressure or diaphragm tension. The unusually low pressure at which they may be operated. The Cunningham Air Whistle is manufactured in five diaphragm diameters. Each increase in diaphragm size gives lower pitch as well as greater intensity of sound. The various lengths within each diaphragm size provide different tones. The short horn gives the high or natural pitch of the diaphragm, while the long horn produces deeper tones. Because of its design, the clear tone of the Cunningham Whistle has a crisp beginning and ending, making it unequaled for coding and echo work. All Whistles are set for operation over a range of 40 to 140 P.S.I.. If Whistles are to be operated at moderately different pressures, simple adjustments can be made at installation.. Cast of solid silicon bronze, and careful workmanship make the Cunningham Whistles remarkably durable. They will give many years of reliable service in a variety of applications. For more information and to hear our Whistles, please continue to our Cunningham Air Whistle website.