Upon looking back at the previous spectral analysis of a guitar signal I realised that this was not much use, as such I decided to carry out the investigation again in order to gain a more useful result.
The spectrogram view in a digital audio editor called Audacity© was used to carry out an investigation on the frequency content of the electric guitar, using a USB audio interface one shot notes and chords were recorded and saved into individual mono tracks. A Hanning window was used with 32768 point Fast Fourier Transform (FFT), adding 50dB gain and reducing the range to 40dB gave an ideal spectrogram showing each individual harmonic and the order in which they fade following the initial impact.
The outcome of this investigation can be found in the screenshots below where the vertical axis represents a logarithmic frequency scale and the horizontal represents time in seconds.
E2 (Hanning, 50dB Gain, 40dB Range, 60 - 3kHz)
C#6 Spectogram (Hanning, 50dB Gain, 40dB Range, 500Hz - 15kHz
Open E2 Chord (Hanning, 50dB Gain, 40dB Range, 60 - 4kHz)
The E2 spectogram proves the fact that a lower frequency entails a longer fade out time or sustain, the fundamental got to an inaudible level after around 30s whilst the 10th harmonic faded after just 3s. Shelquist (2011) states that “Each open string vibrates at a frequency which is directly proportional to the strings tension”, from this a conclusion can be made that the E2 string will have a lower tension and therefore less vibrational inertia.
The C#6 portrays a similar pattern but also, as the 21st fret of the E4 string, it contains far fewer harmonics and sustains for just four seconds. The impact frequencies surrounding the fundamental and first harmonic are much more pronounced in this case. In the E2 chord spectogram the short time delay between each string impact is perceivable from low to high frequencies up to 0.5s, the blue areas indicate impact noise and far higher number of harmonics as a result of the combined string displacements.
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