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The term whistle usually refers to a one-note woodwind instrument which produces sound from a stream of forced air. (For the sound produced with the mouth, see whistling and whistled language.)

Many types exist, from small police and sports whistles (also called pea whistles ), to much larger steam whistles used on locomotives and ships. They are not usually considered 'musical' as such, but musical versions that work on the same principle exist, including any of several 2- octave musical instruments known as tin whistles (sometimes known as pennywhistles or low whistles), organ pipes and the recorder. Pea whistles are used in jazz and Latin music as combination reedReed instruments are musical instruments; they are members of the woodwind family. The performer produces tones on these instruments by blowing air past a cane reed, which vibrates. Pitch is changed by opening or closing holes in the body of the instrumen and percussionPercussion instruments are played by being struck or shaken. They are perhaps the oldest form of musical instruments. Some percussion instruments play not only rhythm, but also melody and harmony. Classifications Most percussion instruments have a distinc instrumentAn instrument is a concrete or abstract tool intended for a purpose other than mechanical work, in particular a refined one. Musical instruments are devices designed to produce music, frequently by plucking or striking a string or bell or drum surface, or.

The whistle works by causing the smooth flow of air to be split by a narrow blade, sometimes called a fippleA fipple is a mouthpiece that uses a narrow windway and a blade-like edge to channel and vibrate air blown into it. It is commonly found on end-blown woodwind instruments such as the tin whistle and the recorder. Woodwind instruments., creating a turbulentFluid dynamics In fluid dynamics turbulence or turbulent flow is a flow regime characterized by low momentum diffusion, high momentum convection, and pressure and velocity variation with time. Flow that is not turbulent is called laminar flow. The ( dimen vortexFluid dynamics This is an article on the real vortex phenomena. For information on the fictional aliens from the Ecco the Dolphin video game franchise, see Vortex life forms . For the VORTEx project, see the Versatile Ocean Subsea Robot for Technical Expe which causes the air to vibrate. By attaching a resonantThis article is about resonance in physics. For other uses, see Resonance (disambiguation). In physics, resonance is an increase in the oscillatory energy absorbed by a system when the frequency of the oscillations matches the system's natural frequency o chamber to the basic whistle, it may be tuned to a particular note and made louder. The length of the chamber typically defines the resonant frequencyFrequency is the measurement of the number of times that a repeated event occurs per unit time. To calculate the frequency, one fixes a time interval, counts the number of occurrences of the event within that interval, and then divides this count by the l. A 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.

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

Sometimes, unintentional 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 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.