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Danish Dave: >I have noticed that some elctric gutars (Klein, Anderson etc etc) > have hollow bodies without f-holes (chambered bodies) what > affect does this have on the sound ?? It improves resonance. Resonance occurs for single solid objects when they experience maximum physical vibration for a given input (so a struck string vibrates at its resonany frequency). Solid guitars have two main resonance sources - the neck (which swings up and down like a twnaged ruler) and the body (which vibrates not unlike a drum head). The frequency spectrum of resonance and antiresonance couples with the frequencies (fundamentals and harmonics) produced by the vibrating string to make a guitar sound more complex. This is why really rigid guitars (eg graphite, and to a lesser degree, maple) have a repulation ofr sounding "sterile" - there is not tonal colour to the sound. Adding tone chambers has two effects - you make parts of the body much freer to vibrate (where the top thins for the tone chamber, you get a miniature "sound board" effect), and it inroduces the idea of there being several coupled masses with flexible parts between them (ie the solid bits and the hollow bits). Finally, the air gaps actually also haver their own resonant frequencies. So a hoollowed out guitar is going to have a far more complex tonal fingerprint, becahse you have lots of different resonances with lots of different frequencies. What happens is that when the string (fundamental or harmonic) frequency matches a (neck or body) resonance it vibrates the neck or body, which you can often feel of yuo're holding the part in question. Since energy is being lost in driving the body part, it is "sucked out" of the string - this is known as parasitic energy loss, from string to body (or neck). Since you have more resonances (and as the guitar is more flexible, they cause even more energy loss), you have a lot of dynamic range - some frequencies are a lot louder than others - and this makes the guitar sound more "lively". It also makes the guitar sound more acoustic - resonance in acoustic guitars is a real mess (since what you hear is the top, back and soundhole resonating) but is nevertheless based on a similar principle. Mike (Lecturer in Mechanical Engineering, University of Surrey)