Non-harmonicity

Non-harmonicity refers to the deviation of a sound's overtones (harmonics) from a perfect harmonic series. In a perfectly harmonic sound, the frequencies of overtones are integer multiples of the fundamental frequency (the base tone). Non-harmonicity results in overtones that are *not* precise multiples of the fundamental, creating a more complex and often dissonant sound. This deviation is especially common in the sounds produced by struck or plucked instruments, where the physical properties of the instrument's vibrating components influence the overtone frequencies. The extent of Non-harmonicity significantly shapes the timbre, or perceived sound quality, of musical instruments and other sound sources.

Non-harmonicity meaning with examples

• The distinctive sound of a piano hammer striking a string includes a degree of Non-harmonicity due to the string's physical stiffness. This contributes to the piano's rich, complex sound, giving it a unique character compared to a perfectly harmonic instrument. The slight detuning of the overtones adds to the instrument's acoustic profile, giving it its tonal quality, that is more than just the perfect pitch.
• In the design of church bells, engineers carefully consider non-harmonicity. Slight deviations from the harmonic series can produce an 'inharmonic' ring, while proper design can reduce it, aiming for a pleasant and clear sound. The bell's shape and the material from which it is constructed impact these nuances to the overall tone in a significant way.
• Guitar strings, when plucked, exhibit non-harmonic behavior. The thicker strings show more prominent Non-harmonicity than the thinner ones. These differences in their vibrational properties play a key role in the overall sound of a guitar. Non-harmonicity is one factor determining the instrument's distinctive and recognizable voice.
• Software synthesizers often incorporate Non-harmonicity parameters. These parameters allow sound designers to simulate the complex timbres of acoustic instruments, such as pianos, by introducing subtle frequency variations in the overtones. This provides a means of manipulating the tonal color and complexity of the sounds produced.