4. Resonance

Resonance is a key concept in the production of sound in instruments and in acoustics. We will come across it many more times in this book. The natural frequency (f0 measured in Hertz) is the frequency at which an oscillating system naturally wants to vibrate. For a mass on a spring, this is determined by the stiffness of the spring; a stiffer spring has a higher natural frequency as we saw in the previous chapter. To keep a system vibrating in the presence of friction we have to keep pushing it with a periodic force. The frequency of this periodic driving force is called the driving frequency, f which is totally independent of the natural frequency (we can push our mass on a spring at a frequency different from the frequency at which it wants to vibrate).

Key Terms:

Natural frequency, driving frequency, angular frequency, damped harmonic motion, driven harmonic motion, resonance, resonator, Helmholtz resonance, Quality or Q-factor.

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