I am often asked the question: “How do I know what frequency my singing bowl is”? Well, actually a Tibetan Singing bowl produces several frequencies. Most bowls (but not all of them) are tuned to a flatted fifth, also known as a Tritone. So, the “struck tone” of a singing bowl is a contradiction in terms, because when struck, a singing bowl produces a chord, or interval.
The predominant tones we hear in singing bowls are a flatted Fifth interval, also known as the Tritone. This interval was referred to as “the Devil’s Chord” and was outlawed by the Catholic Church in the 17th Century. But the graduated diameters of singing bowls produce layers of rich additional overtones, which, when heard binaurally, create beat frequency which alters our brain waves from a Beta brainwave state to an Alpha state, and in some instances, to Theta. Dr. Jeffrey Thompson, founder of the Center of Neuroacoustic Research wrote an amazing white paper on the effects of binaural beats on brainwaves entitled “Acoustic Brainwave Entrainment with Binaural Beats” which is a great resource to learn more on the physics of brainwave entrainment.
So unlike Crystal singing bowls, which are almost pure sine wave with a 3rd interval harmonic, Tibetan singing bowls are rich in layered frequencies. The lower tone of the bowl (the fundamental) is produced by rubbing a leather mallet around the outside wall of the bowl; the female overtone (the bowl’s highest voice) bowl is produced by pressing the wooden part of the mallet along the outside edge of the bowl’s lip. There is usually also a mid-tone present in medium size to large bowls, with multiple frequencies in between. This tone will usually come up when you begin to play a medium sized bowl around the lip, and then after the bowl is warmed up it will resolve to the female overtone and jump an octave. With some high-wall (“Jambati”) type singing bowls, you can often isolate this tone with a leather mallet.
To meter each frequency, first of all, we have to isolate it. We usually use a Boss guitar tuner, unless someone wants to know the exact Hertz of a bowl, in which case we’ll use Peterson software on a computer or iphone. The more sophisticated software will home in on the bowl’s broad waveform and list it. If you’re using a more primitive guitar tuner, you’ll have to get a clean, isolated tone first, let it peak, and then start to decay before the tone will even out enough for the tuner to lock in and measure it. But remember: every singing bowl frequency is still a moving target. Any measurement we take is only a snapshot of a moving wave form.
The frequencies you see marked on each singing bowl in Bodhisattva’s web store are measured by the whole or half tone, plus the number of Hertz (in multiples of two) either flat (marked by a minus -) or sharp (marked by a plus +) of the note. If the frequency is concert pitch, we list the first 3 digits of the frequency’s Hertz value. So a middle C would be marked C 261 Hz., for example. If it were 2 Hz. sharp, it would be listed as a C +2 Hz., and so on.
Each whole tone is divided into a half tone (a sharp) and two quartertones (we don’t use these in Western music for the most part). So you might see some of our sets built on quartertones: a whole note plus, or minus 10 Hz. Here’s another trick to watch out for on our site: a sharp + 10 is the same thing as the next whole tone up minus 10 Hz. Here’s what it looks like: A# +10 = B -10 Hz. These notations are exactly the same tone, but they are used differently depending on what scale they’re in.
The frequencies produced by the bowl are determined by the bowl’s diameter, shape and density of its metal. All three of these factors affect each other. Generally speaking, the larger the bowl’s diameter the deeper sounding the bowl. But the density of the metal counts, too: the thicker the bowl, the higher the pitch.
Dr. Jeff Thompson once observed that the graduated diameters of the bowl actually produce a singing bowls’ harmonics. That explains why the slope of the bowls wall can affect how many harmonics there are in a bowl. For example, smaller Cup bowls which are 4 – 5″ diameter will only have two distinct harmonics. “Thadobati” type singing bowls usually have three: the fundamental, the female overtone, and a mid-tone. A High-wall, Low-wall-Thick-lip, or a Lotus type singing bowl with a broad slope at its base will have many more audible harmonics, and starts to sound more gong-like in timbre, as opposed to bell-like.
Because the ancient ones were handmade, then, their construction varied slightly with each and every bowl. Their intervals are like voice patterns; no one voice is exactly the same. So the pitches of the bowls were determined at the time they were made, and cannot be altered unless you subtract metal from the bowl (by sanding the basin of the bowl, for example). Ancient bowl makers also altered the bowls’ frequencies by creating “hatch marks” in the sides of the walls.
Knowing the frequencies of your bowl is really helpful if you want to add bowls to your collection, if you’re playing bowls with Western instruments, or if you want to find out what Chakra your bowl resonates with. But that’s the extent of its usefulness. Do you think the monks at Drepung Loseling Monastery cared which frequencies they were playing? So once you know the frequencies of your bowl, just let it go! Thank your left brain for retaining that information and get back the business of becoming one with the sound.