The short answer
Wall and rim thickness affect a bowl’s stiffness and therefore its resonant behaviour, but thickness cannot be interpreted independently of radius, height, curvature and material. Simplified singing-bowl models predict increasing modal frequency with thickness and decreasing frequency with increasing radius. Real handmade bowls should therefore be measured as complete structures rather than judged from one dimension.
Acoustics / physics
Thickness raises frequency, radius lowers it
Acoustics / physics
A thicker wall is stiffer for the same span, and greater stiffness raises modal frequency. A larger radius gives the wall more distance to flex over, which lowers it. In simplified models of singing bowls these two act in opposition, which is why a thick small bowl and a thin large one can land closer together than their diameters suggest.
Thickness is not one number
Measured by ANURAVA
On a hand-raised bowl the wall thickness varies with height and around the circumference. A single rim measurement is a sample, not a specification. This is why the measurement protocol records rim thickness at four approximately equally spaced positions and keeps the mean and the range — the range is the informative part, because it describes the asymmetry that produces beating.
Why it cannot be read alone
Thickness only has meaning alongside radius, height, curvature and material properties. Quoting it in isolation implies a precision the figure does not carry. The useful use of a thickness measurement is as one term in a description of a whole structure, and as a record of how much the wall varies.
Cross-section
Frequently asked
Does a thicker bowl sound higher or lower?
Higher, all else being equal, because a thicker wall is stiffer and stiffness raises modal frequency. All else is rarely equal, since radius pushes the other way.
How does rim thickness affect sound?
It contributes to the stiffness of the vibrating wall and therefore to modal frequency. Variation in thickness around the rim also splits paired modes, which is heard as beating.
Why should rim thickness be measured?
Because a single figure hides the variation that matters. Measuring at several positions and recording both mean and range describes the asymmetry that gives a hand-raised bowl its character.
Sources & methodology
- Peer-reviewed acousticsTerwagne & Bush, ‘Tibetan singing bowls’Nonlinearity / MITModels bowl vibration from radius, height, wall thickness, stiffness and density; tapping excites multiple modes, rubbing preferentially excites one.
- First-partyANURAVA Acoustic Method v1.0 and Sound Passport recordsANURAVAFirst-party measurement protocol and per-instrument documentation.
Written and reviewed by ANURAVA. Where a statement rests on a musical convention or a traditional association rather than on measurement, it is labelled as such in the text above.