Two doubts: First, when the hammer hits any string, the string begins to vibrate, until here, no problems, but, the vibration decays over time and this decay is linear, exponential or assume another form? Second, when the hammer hits a string and the string begins to vibrate, it vibrates in fundamental frequency, in resonance frequency, and we heard this vibration. But we heard other vibrations too, that is mutiples of the fundamental frequency. So, when the hammer hits the string of 440 Hz, for example, we heard vibrations in 440 Hz, 880 Hz, 1320 Hz, 1760 Hz, 2200 Hz and so on. But in terms of sound intensity, what is the relationship between the fundamental frequency and the multiple of the fundamental frequency? I ask this because the amplitude of the multiple of the fundamental frequency is not equal the amplitude of the fundamental frequency. Probably, shoud exist a decaying relationship between the amplitude of the fundamental and its multiples. EDIT: See this ilustration (https://upload.wikimedia.org/wikipedia/commons/a/a4/Espectro_harmónico.jpg), but I don't know if this graphic is correct or not.