What is a wolf tone? Why and how does a wolf tone occur?
The wolf tone is a wavering – similar to the change between a developing and collapsing tone – of the vibration in the strongest main resonance of the instrument’s body.
Different instruments have different wolf tone areas:
- Violin and viola: both instruments should not have a wolf tone, but it frequently occurs. There are up to two wolf tone areas here, and up to three buzzing areas. A wolf tone is always located on the main resonance of the instrument. For violins, this is usually the G-string, or sometimes the D-string. For violas, it is the G-string or sometimes the C-string.
- Cello: The cello has a significant wolf tone area. This is normally located on the G-string.
- Double bass: That’s the most prone instrument to the wolf tone. It has up to five wolf tone areas. In principle, the wolf tone can occur anywhere, but it is particularly problematic on the E-string.
The wolf tone is an interaction of string and soundboard vibration, like with a dance couple whose steps must match rhythmically. A wolf tone occurs in instruments, whose soundboard has too little damping. The cause is the coupling of the string vibration and the vibration of the insufficiently damped soundboard. As a result, the vibration of the string and the soundboard do not fit together and the vibration collapses - comparable with a dance couple where one suddenly stands on the other’s foot and the whole vibration, the dance itself, is interrupted.
To produce lots of sound colors and overtones, a cello needs a wolf tone and a bass needs a number of wolf tones. However, violins and violas do not need it. The reason is the size of the instrument – to be exact, the relationship between the soundboard size and the soundboard thickness. The larger the instrument, the thinner the soundboard in comparison (in brief: the surface of the soundboard increases, but the thickness of the soundboard does not increase proportionally). As a result, the damping is reduced. And, as you now know, a wolf tone occurs in instruments, whose soundboard has too little damping.