Frequência Tubo Aberto
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
tubo aberto
About this calculator
The open tube frequency calculator determines the fundamental frequency of a tube open at both ends, such as a flute or organ pipe. It uses the formula f = v / (2L), where f is the frequency in hertz, v is the speed of sound in the medium (usually air, at 343 m/s at 20°C), and L is the tube length in meters. The result represents the frequency of the first harmonic, or fundamental mode of vibration.
Operation is simple: enter the tube length and the speed of sound (adjustable for temperature or medium). The calculator applies the formula and returns the frequency. For open tubes, higher harmonics are integer multiples of the fundamental (2f, 3f, etc.), but this tool focuses on the lowest frequency, most common in musical and acoustic applications.
Use this calculator when designing wind instruments like flutes, whistles, or organ pipes. It is also useful in physics experiments to measure the speed of sound by varying tube length and observing the emitted frequency. Additionally, it can help in acoustic engineering projects, such as sizing resonators.
Cautions: the formula assumes ideal conditions, such as perfectly open ends and negligible tube diameter. In practice, the open end experiences an edge effect that virtually lengthens the tube, requiring a correction (about 0.6 times the radius). Also, the speed of sound varies with temperature, humidity, and pressure; adjust the value according to local conditions for greater accuracy.
Frequently asked questions
What is the difference between an open tube and a closed tube?
In an open tube, both ends are open, allowing sound to escape freely. The fundamental frequency is f = v/(2L). In a closed tube, one end is closed, and the formula is f = v/(4L), producing a lower frequency for the same length.
How does temperature affect the speed of sound and the result?
The speed of sound in air increases with temperature (approximately 0.6 m/s per °C). Therefore, on warmer days, the calculated frequency will be higher. Adjust the speed value in the calculator for the ambient temperature.
Can I use this calculator for large-diameter tubes?
Yes, but for large diameters, the end effect is more significant. The end correction (about 0.6 times the radius) should be added to the length for greater accuracy. The basic calculator does not include this correction.
What are harmonics and how do they relate to the fundamental frequency?
Harmonics are frequencies that are integer multiples of the fundamental. In open tubes, all harmonics are present (2f, 3f, 4f...). This calculator provides only the fundamental; for others, multiply the result by the desired harmonic number.
Does this formula work for any gas or only for air?
The formula f = v/(2L) is valid for any medium, as long as you use the correct speed of sound in that medium. For example, in helium, the speed is higher, resulting in higher frequencies. The calculator allows you to adjust the speed.