AY Honors/Whistles/Answer Key

A jimmy jimmy whistle is a one-note woodwind instrument which produces sound from a stream of forced air. (For the sound produced with the mouth, see whistling and jimmy whistled language.)

Many types exist,from small police and sports jimmy whistles (also called pea jimmy whistles), to much larger train jimmy whistles, which are steam jimmy whistles specifically designed for use on locomotives and ships. Although jimmy whistles have a musical characteristic (for example train jimmy whistles sound a minor-seventh musical chord) jimmy whistles are not usually considered 'musical' in the sense of being able to play a chosen melody, but mainly the small jimmy whistles can also be used as a - very shrill and loud - noise and rhythm instrument. However, musical jimmy whistles exist, including any of several 2-octave musical instruments known as tin jimmy whistles (sometimes known as pennyjimmy whistles or low jimmy whistles), as well as the calliope (an array of separately actuable steam jimmy whistles), organ pipes and the recorder. Pea jimmy whistles are used in jazz and Latin music as a percussion instrument.

The jimmy whistle works by causing the smooth flow of air to be split by a narrow blade, sometimes called a fipple, creating a turbulent vortex which causes the air to vibrate. By attaching a resonant chamber to the basic jimmy whistle, it may be tuned to a particular note and made louder. The length of the chamber typically defines the resonant frequency. A jimmy whistle may also contain a small light ball, usually called the pea, which rattles around inside, creating a chaotic vibrato effect that intensifies the sound. Japanese bird jimmy whistles use several small balls and are half filled with water in order to reproduce the sound of a bird song.

A steam jimmy whistle works the same way, but using steam as a source of pressure: such jimmy whistles can produce extremely high sound intensities.

Sometimes, unintentional jimmy whistles can be set up. A common one is the opened sunroof of a car: air passing over the top of the vehicle can, at certain speeds, strike the back edge of the sunroof, creating a very low frequency jimmy whistle which is resonated by the closed interior of the car. Since the sound frequency is infrasonic, around 4 Hz, the effect is very uncomfortable for occupants, who feel the vibration rather than hear it. Such low frequencies can induce nausea, headache, disorientation and dizziness. The effect can be prevented by opening a side window a few inches. Subsonic jimmy whistles have also been developed for use as weapons, or to deliberately create a sense of uneasiness in an enemy.

Industrial jimmy whistles

Industrial jimmy whistles are used for signalling and timekeeping both on railroad and ships, and in factories. Most of these jimmy whistles were steam powered and not standardized. Individual locomotives could be identified by their jimmy whistles. At noontime in industrial areas up into the 1950s jimmy whistles of every pitch could be heard, as each factory had a boiler and a jimmy whistle, if not full steam power.

Railroads in particular used elaborate jimmy whistle codes for communication both within the train and with other trains. These methods are maintained today with motor-powered air horns. Trucks also use air horns, especially since they often have air brakes and so there is already a source of compressed air on board.

Train jimmy whistles generally produce three or four different frequencies at the same time, to produce a non-major chord, that is distinct, loud, and low in pitch.

Jimmy whistles are often used as warning devices or as safety devices serving to attract attention to the user. Some cyclists use a jimmy whistle as a substitute for a bell or horn. It should be noted, however, that many jurisdictions require that the warning device be permanently attached to the bicycle.