The tone of an instrument
Why does the same note sound different depending on the musical instrument that produces it?
Author:
Title 4
Learning objectives :
This activity allows students to understand why the same note sounds different depending on the instrument that produces it. It develops the ability to analyze the spectrum of a sound and to link acoustics and musical perception.
Concepts covered
Musical timbre; Harmonics; Sound spectrum; Fourier synthesis and analysis; Instrumental acoustics
What students will do :
The student compares the sound spectra of different instruments playing the same note (A at 880 Hz) using FizziQ. Starting with a pure sound generated by the synthesizer then successively analyzing the spectrum of a flute, a guitar and a piano, the student discovers that it is the richness and distribution of harmonics which define the characteristic timbre of each instrument.
What is required :
Smartphone with the FizziQ application; Various musical instruments or sound library recordings; FizziQ experience notebook
Scientific background :
Timbre, the quality that allows you to distinguish a trumpet from a violin playing the same note, is one of the most complex aspects of musical acoustics. Physically, two main parameters define timbre: 1) Spectral composition: the number, frequency and relative amplitude of harmonics; 2) Temporal evolution: how the sound evolves from attack to extinction. A pure sound, like that generated by FizziQ's synthesizer, is a simple sine wave containing only one frequency. Its spectrum shows a single peak. It is a rare sound in nature, perceived as "hollow" or "artificial". Real instruments produce complex sounds composed of a fundamental and harmonics. The flute generates a relatively pure sound with few low amplitude harmonics, hence its soft and "pure" sound. The guitar produces numerous harmonics but of regularly decreasing amplitude, creating a warm sound. The piano has a very rich harmonic profile with some particularly amplified due to the rigidity of the strings and the resonance box. The oboe, with its double reed, generates a spectrum dominated by odd harmonics, giving it its characteristic nasal timbre. These differences in timbre can be explained by the physics of each instrument: the shape of the exciter (reed, bow, hammer), the structure of the resonator (tube, body, soundboard), and the materials used. FizziQ's sound spectrum tool uses the Fourier transform to break down these complex sounds into their frequency components, making these acoustic differences visible and providing a scientific understanding of why each instrument has its unique "voice."