The relationship between size and tone in singing bowls
The frequency, tone, or note of a singing bowl is based on multiple factors that sometimes work against each other to come up with surprising results. The most basic relationship between singing bowl size and frequency is the bigger the bowl the deeper the tone. Big bowls like Jambati and Ultabati styles, which can be from 8 to 15 inches are the deepest in tone, down into the 2nd octave – as low as 60 Hz. Tiny bowls like Thadobati and Mini Mani are the highest tone up into the 6th octave or over 1000 Hz.
The relationship between thickness and tone in singing bowls
This relationship can be surprising. The thicker the bowl the higher the tone. This will work against the simplistic idea that all that matters is size. So if you have two bowls at 8 inches each the thick one will be at a higher tone. How much higher? it can be huge, an octave or more. In Jambati style thin 12 inch bowls can be intensely low, near the bottom of the range for all bowls and the same size bowl if super thick can hit the 4th octave, same as a 4 1/2 inch thin Thadobati.
The relationship between shape and tone in singing bowls
Another variable to consider is one that is not necessarily linear like size and thickness. The style that most showcases this relationship is Mani. The full size version of those bowls at 6 to almost 9 inches across are very high tone, mostly 5th octave. You can find huge bowls that are 1000 Hz. The same thickness in another style, Thadobati never gets to even to the top of the 4th octave let alone double the frequency. The difference is Thadobati are open at the top while the Mani shape closes the aperture at the top of the bowl. Mani bowls often put more weight into the side walls than Thadobati, that may be a factor, too but it could not account for the consistency of this relationship, Thadobati lower than Mani. This relationship plays out in deep bowls, too with the more open Ultabati often coming in at a lower frequency than the same size and thickness Jambati.re big,
The relationship between metal and tone in singing bowls
Here I have to get into speculation because I’ve not seen enough metallic assays to have clear judgements. My speculation is the higher on the periodic table the higher the tone. All antique bronze bowls have copper and tin, This would mean bowls relatively high in tin (50) vs copper (29) wuld have a higher tone. I do have some data on bowls that contain iridium, a non-radioactive rare earth metal (77). I’m not sure about frequency but they definitely have amazing resonance. In old England they had half ton silver (50) church bells, almost pure I would imagine they had amazing sound.