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Module 1: Sonido - ondas

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Columnas de aire boca

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Physics - Open-end air columns

Open-end air columns

When these air columns are excited by blowing across one end, sound waves
travel along the length of the air column. When a sound wave reaches the
other open end, some of its energy is reflected back down the tube due to
the sudden change in air pressure at this location. Numerous sound waves
therefore travel to and fro along the tube, interfering with each other and
creating a standing wave. This standing wave has a pressure node at each
end of the pipe, and a pressure antinode mid-way between them. See the
diagram below. This is called the fundamental frequency of the pipe of the
first harmonic. Higher harmonics occur with more complex standing wave
patterns. The frequency of harmonic is a whole number multiple of the
fundamental frequency. When the pipe is resonating, a number of harmonics
occur simultaneously. The diagram shows the relationships between
frequency, wavelength and pipe length.

Standing waves in air columns can be considered in terms of particle
displacement, also called amplitude. Maximum amplitude of vibration (a
displacement antinode) occurs at the two open ends of the pipe, that is
where pressure nodes occur. The displacement nodes will occur midway
between these, where the pressure antinode occurred.

In summary, for standing waves in air columns:

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