Fundamental Frequency vs Natural Frequency
Natural frequency and fundamental frequency are two wave related phenomena that are very important. These phenomena are of great significance in fields such as music, construction technologies, disaster prevention, acoustics and most of the natural system analysis. It is vital to have a clear understanding in these concepts in order to excel in such fields. In this article, we are going to discuss what fundamental frequency and natural frequency are, their definitions, applications, the phenomena connected to natural frequency and fundamental frequency, their similarities and finally the differences between natural frequency and fundamental frequency.
What is Natural Frequency?
Every system has a property called the natural frequency. The system will follow this frequency, if the system is to be provided with a small oscillation. The natural frequency of a system is very important. Events such as earthquakes and winds can do destruction on objects with the same natural frequency as the event itself. It is very important to understand and measure the natural frequency of a system in order to protect it from such natural disasters. Natural frequency is directly related with resonance. When a system (e.g. a pendulum) is given a small oscillation, it will start to swing. The frequency with which it swings is the natural frequency of the system. Now imagine a periodical external force applied to the system. The frequency of this external force does not necessarily be similar to the natural frequency of the system. This force will try to oscillate the system to the frequency of the force. This creates an uneven pattern. Some energy from the external force is absorbed by the system. Now let us consider the case where the frequencies are the same. In this case, the pendulum will freely swing with maximum energy absorbed from the external force. This is called resonance. Systems such as buildings, electronic and electrical circuits, optical systems, sound systems and even biological systems have natural frequencies. They can be in the form of impedance, oscillation, or superposition, depending on the system.
What is Fundamental Frequency?
Fundamental frequency is a concept discussed in standing waves. Imagine two identical waves, which are travelling in opposite directions. When these two waves meet, the result is called a standing wave. The equation of a wave travelling in +x direction is y = A sin (ωt – kx), and the equation for a similar wave traveling in the x direction is y = A sin (ωt + kx). By the principle of superposition, the resultant waveform from the overlapping of these two is y = 2A sin (kx) cos (ωt). This is the equation of a standing wave. ‘x’ being the distance from the origin; for a given x value, the 2A sin (kx) becomes a constant. Sin (kx) varies between 1 and +1. Therefore, the maximum amplitude of the system is 2A. The fundamental frequency is a property of the system. At the fundamental frequency, the two ends of the systems are not oscillating, and they are known as nodes. The center of the system is oscillating with the maximum amplitude, and it is known as the antinode.
What is the difference between natural frequency and fundamental frequency? • Natural frequency is a property that concerns oscillations, but fundamental frequency is a property that concerns waves. • Every system has a natural frequency, but the fundamental frequency occurs in only some of the systems. • For the fundamental frequency, the superposition of oppositely travelling two identical waves is required, but for natural frequency, only a single oscillation is required.

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