Felhang

Felhang is a term used in acoustics and audio engineering to describe a sound or tone that is perceived as higher in pitch than the fundamental frequency of a sound source. These are also known as overtones or harmonics. When an instrument produces a note, it does not just produce a single frequency. Instead, it produces a complex sound wave that is a combination of the fundamental frequency and a series of higher frequencies called harmonics. The relative intensities of these harmonics contribute to the timbre or unique sound quality of the instrument.

The fundamental frequency is the lowest and usually the loudest frequency produced by a sound source, and it determines the perceived pitch. Harmonics are integer multiples of the fundamental frequency. For example, if the fundamental frequency is 100 Hz, the first harmonic would be 200 Hz, the second harmonic would be 300 Hz, and so on. While harmonics are theoretically infinite in number, only a certain number of them are audible and contribute significantly to the overall sound. The presence and strength of these felhangs are what allow us to distinguish between different instruments playing the same note, such as a piano and a violin.

In some cases, a sound source might produce frequencies that are not integer multiples of the fundamental. These are called non-harmonic overtones. While less common in musical instruments, they can occur in percussive instruments like bells or drums, and can contribute to their distinct sounds. Understanding felhangs is crucial in fields like music synthesis, audio analysis, and psychoacoustics.