Banjos with aluminum rims, soft wood rims covered in veneers, zinc tone rings, incorrectly fitted tone rings, all defy the basic understanding of how a banjo works and should be avoided. Deering advertises all of the features in our banjos so our customers know what they are buying and why we make banjos the way we do.
We respect traditions. But acoustics must be obeyed whether traditional or not. When shopping for a banjo, ask the dealer or contact the manufacturer and ask them why they build banjos the way they do. Better yet, contact us. We can tell you why we build our banjos the way we do, and our reasons are based in a strong understanding of acoustics and banjo design. Changing your banjo strings is one of the easiest and best ways to bring the tone of your banjo back to life.
One of the most common questions we hear is how Modern banjos have standard head sizes. Vintage banjos on the other hand have head sizes that are all over the map. At Deering we use two different head In this video Chad Kopotic focuses on setting up a Deering Proper adjustment of your banjo's truss rod allows you to put a little bit of concave curve in the neck of your banjo to make the playability a lot easier Banjo Set Up Your Deering.
How Banjos Work. Tone ring or no tone ring is not better or best, just different. Search Blog Post. Read More.
Banjo Set Up , Your Deering. It may be noted that for the membrane wave speed to match the sound speed in air, the fundamental frequency would need to be at least doubled relative to the highest achieved in these measurements. The conclusion is that a Mylar membrane, whether on a banjo or a drum, is always subsonic. Finally, the recordings were processed in the same way used to generate Figure 4 , giving the results plotted in Figure For clarity, only the extreme cases plus one intermediate tension are shown.
For each tension indicated by colour two different taps were analysed and plotted with circle and star symbols respectively to give an indication of repeatability. As before, the magenta line indicates the approximate limit of applicability of the method: points lying much beyond this line will not be reliably detected.
The results tell a clear story. For each tension there is a cloud of points representing a range of possible loss factors at any given frequency.
These clouds overlap, but there is a systematic movement upwards in the diagram as tension increases. This rise in damping is caused by increasing radiation damping. The conclusion for the sound of the banjo is that increasing the head tension will increase the radiation efficiency of all modes, and also change the tonal balance across the frequency spectrum by shifting individual resonances and perhaps by changing the general trend of response with frequency.
Figure 10 Loss factor against frequency for fitted modes of selected examples of the variable tension set. Tensions are indicated by colour as in Figure 8. Circles and stars show results from separate tests. Measured input admittance can be used to synthesise plucked notes. Such synthesis can be used to understand the results shown in Section 2. As has been explored in some detail in previous work [ 30 , 35 ] there are several possible approaches to such synthesis. Two of the methods presented in that work will be used here.
The first method works in the frequency domain, and uses an inverse FFT to obtain the time history of the plucked note. This method can use a measured bridge admittance with no additional processing.
Alternatively, it can use a bridge admittance computed from a theoretical model. The second method works by modal superposition. For admittance derived from theoretical modelling, the modes may be directly available from the model. For a measured admittance like the ones shown here, a modal decomposition must be carried out. This can be done using signal processing methods derived from the fields of system identification or experimental modal analysis see for example [ 34 ].
The result of such a modal fit to a measured banjo admittance was shown in Figure 6. The simpler, faster and more robust frequency-domain approach cannot give this information.
The modal-based approach uses separate degrees of freedom for the string and body, so for any given coupled mode of the combined system it is easy to compute the fraction of total potential energy associated with the string degrees of freedom. If that fraction is bigger than 0. In almost all cases the energy fraction is very close to zero or 1, making the distinction uncontroversial.
The synthesised pluck sound is created by a linear superposition of all the modes, so if desired the string modes and the body modes can be separately summed before being combined to give the final sound. Sound examples will be discussed in Section 3. There is a further subdivision of synthesis methods, depending on whether string vibration is confined to a single polarisation plane, or whether both polarisations are included.
There is no doubt that a 2-polarisation model captures more of the physics of the instrument. Examples of the effect of including the second polarisation are included among the sound demonstrations see Sect. The results to be presented here and on the web site [ 3 ] give a strong indication that recognisable banjo sound can be produced by this simpler modelling option.
For all approaches to synthesis, properties of the strings are needed: relevant properties of guitar strings have been published previously [ 15 ], while properties of the banjo strings are listed in Table 2.
The main missing ingredient is a model for the intrinsic damping of the banjo strings. A suitable model was fine-tuned by comparing the results of synthesis with measurements of real plucked notes: the details will be presented in Section 3. Exploration of these varieties of synthesis model requires two stages: the first based on measurements, the second based on listening to the resulting sounds.
It is a common experience in musical acoustics that features which show up very clearly in acoustical measurements do not necessarily produce large audible effects, while conversely some effects that are perceptually important can be remarkably hard to pin down by measurements. It has been seen in Figure 5 that the bridge admittances of guitars and banjos are significantly different. To see how this translates into different behaviour when the instruments are played in the normal way, the distribution of loss factors shown in Figure 4 , deduced from playing chromatic scales on the top strings of the banjo and guitar, can be compared with estimates derived from modelling.
The measured clouds are plotted again in Figure 11 for the guitar and the banjo separately: two sets of plucked notes were recorded for each instrument, and processed independently to give an indication of consistency of the measurements: the two sets are plotted as red circles and stars, and a reassuring correspondence can be seen between the two over the important parts of both plots.
Figure 11 Loss factor versus frequency for modes excited by plucking the top string of a the guitar; b the banjo. Red circles and stars: measured values; blue stars: values from synthesised notes; black dots: predicted loss factor for energy flow into the body alone, calculated from the measured admittances shown in Figure 5. Blue dashed line in a shows the internal loss factor of the string.
The blue and black points in these plots show theoretical estimates of two different kinds. The black points show estimates of the contribution to the loss factor arising only from energy flow from the string into the instrument body, calculated from the measured bridge admittance.
The blue points in Figure 11 are the result of repeating the chromatic scale experiment using the frequency-domain synthesis model, and processing the results with the identical analysis code used for the experimental observations so they are again limited to the region below the magenta lines.
These points can be directly compared to the measured red points, and they also serve to give an internal check both on the synthesis code and on the signal processing method, by comparing with the black points. Both blue and black points are computed, by very different approaches, using the same bridge admittance, so the blue points should always lie above the black points because the synthesis model allows for additional energy loss in the string. But this additional loss is quite small, so when the black points predict relatively high loss factor, the blue points would be expected to follow them.
These expectations are reassuringly confirmed in the plots, most clearly in the banjo case. The plots tell an interesting story. It is simplest to explain the guitar case first, Figure 11a. The body modes often show as clusters of many points, because in principle these modes are excited by the transient nature of every plucked note, regardless of the played pitch, so that many estimates of these modes are obtained from the chromatic scale.
Strictly, each body mode is not exactly the same for every played note, because it is perturbed by coupling to the string. However, except for special cases where a string overtone falls very close to an unperturbed body mode, the shift is small. The blue and red points agree quite well for these body mode clusters. Probably the line of points would continue approximately horizontal beyond the magenta line but for the limitations of the analysis technique.
The string modes consist of an approximately harmonic series based on the fundamental of each successive note so that the plotted points are spread out along the frequency axis.
The body modes have Q-factors inverse of loss factors around or lower, while the string modes have Q-factors of a few thousand and their decay times determine the duration of each played note. It is very striking in Figure 11a that the line of the string modes is fairly featureless, and mostly lies significantly above the black points. This confirms something reported earlier for guitars it is true for both steel-string and nylon-string guitars [ 37 ]: rather unexpectedly, the decay rate of string modes in these instruments is dominated by the damping of the string itself, and loss into the body of the instrument is usually only a small perturbation.
There are exceptions where the guitar body has a strong resonance, but it should be noted that this particular plot is confined to the frequency range relevant to the top string, and the strongest body resonances of the guitar lie lower in frequency.
The blue points for string modes follow the red points closely, but this is no coincidence: this data was used to fine-tune the damping model for the string used in the synthesis model.
Earlier work investigating a range of polymer-based musical strings demonstrated that a rather simple model for the intrinsic damping of the strings gave excellent agreement with measurements [ 38 ]. A version of that damping model has been successfully adapted for the steel strings played here: the loss factor resulting from this model is shown as the dashed blue line in Figure 11a.
The total modal loss factor is estimated by. The air damping term is given by Fletcher and Rossing [ 19 ] in the form. Energy loss from viscoelasticity in the string arises from the influence of bending stiffness.
The plot for the banjo, Figure 11b , is strikingly different from the guitar case. The black points lie considerably higher over much of the frequency range, as a direct result of the higher input admittance of the banjo.
There is still a trace of two lines showing string modes and body modes, but whenever the black curve crosses above the position where the line of string modes occurred for the guitar, it carries the actual loss factors up with it. Energy dissipation arising from different physical mechanisms is additive, so in theory the total loss factor cannot be lower than the black curve.
In the main this expectation is borne out by the data. There are a few red points lying below the black curve, especially in the frequency range around 1 kHz, but these may be associated with an aspect of the physics not taken into account in this simple description: each string mode can occur in two different polarisations. The description here, and the basis for the calculation of the black points, considers only the string polarisation normal to the head. Vibration in the plane parallel to the head is likely to couple much less strongly to the head, and thus exhibit lower loss factors.
The real plucks during the test procedure will involve a mixture of both polarisations, this being the explanation of the beating behaviour noted in Figure 2b. Perhaps a few peaks associated with the second polarisation have been caught by the analysis. Simple experiments using the two-polarisation synthesis method confirm that this kind of effect can indeed occur, but it would require more careful and systematic efforts to attempt a quantitative validation comparison.
This lies beyond the scope of the present work. There are several consequences for the behaviour of notes played on the banjo. For frequencies up to about 1 kHz, the string modes often have significantly higher damping than for the same string attached to a guitar.
The decay time will be faster, and at some frequencies it will be so fast that the distinction between string modes and body modes is lost: this is flagged in the plot by the black points reaching levels comparable with the line of body modes.
Secondly, over most of the frequency range plotted here the string modes follow the black points quite closely. This means that most of the energy put into the string is lost by being transferred to the body, whereas in a guitar most of it is dissipated by other loss mechanisms.
Furthermore, it will be shown in the companion paper [ 2 ] that radiation damping for many modes of the banjo head dominates over structural damping, so a significant proportion of this energy from the strings is radiated as sound.
The result of these two factors taken together is that a note played on the banjo with the same player gesture as a note on the guitar will sound louder, and decay faster. But there are probably other important factors, not made apparent by this particular analysis.
Physical measurements are never enough to settle perceptual questions: it is necessary to listen to the sounds from the synthesis model and find out if they do in fact strike listeners as convincingly banjo-like. To accompany this discussion, the reader is referred to Section 5. Here is a link to the audio instead. It makes use of the measured admittance in the red curve of Figure 5 , and it is the crucial first test of whether the synthesis method can give plausible banjo sounds.
This can be compared with sounds based on other measured admittances from this banjo, in Sounds C. These include cases with and without the resonator back, cases measured at different points on the bridge, and cases in which the regular bridge was substituted for a rigid circular bridge. This circular bridge is pictured on the web site; it will be used in the companion paper [ 2 ] as a validation case for modelling.
This contrasts with Sounds C. The difference is striking. It seems unlikely that any listener would mistake any of these sounds for a banjo. Sounds E. The last of these sounds the most distinctive, which is not surprising given that it will be dominated by the horizontal bridge admittance plotted in black in Figure 7. Sound E. They give an opportunity to hear the separate sounds of the string Your browser doesn't support HTML5 audio.
This comparison gives a useful insight. On a casual listening, the string-only sound is quite similar to the full synthesis with all modes, which is indistinguishable from the frequency-domain datum sound presented above. However, the difference is clearly audible, if hard to put into words.
Figure 12 shows spectrograms of the synthesised passage for the string modes and the body modes separately. They reveal that it is hardly surprising that some difference can be heard when the body modes are included. Body modes are strongly excited over a frequency range extended up to about 2 kHz, and although they generally have much faster decay times than the string modes, typical banjo music like the passage used here has notes that come thick and fast, and the body modes ring on for long enough to bridge the gap to the next played note.
Figure 12 Spectrograms to illustrate modal synthesis: a string modes only; b body modes only. Note that this body mode contribution to the sound gives a possible mechanism for recognising a particular instrument, to some extent independent of what music is played.
The mix of body modes is similar for every note, and constitutes a kind of acoustical fingerprint of the instrument. A similar mechanism has been suggested for distinguishing different violins by their transient sound [ 40 ]. For the banjo, Figures 2a and 12 suggest that the effect may extend over a wider frequency range, but this has yet to be formally tested. The next set of sound demonstrations, Sounds F. Rather than using measured admittance, they use a theoretical model in order to give access to parametric variations.
The various sound examples illustrate the effect of varying the size and tension of the banjo head, and also the mass of the bridge and the added stiffness due to axial effects in the strings, in-plane effects in the head and string tension. The details are described on the web site. An important conclusion emerges, illustrated by the admittance plots in Figure Adjustments that affect individual resonances but which do not change the low-frequency formant, like the examples shown in Figure 13a , have a relatively subtle effect on the sound, whereas adjustments that change this formant, like those shown in Figure 13b , have a more pronounced effect.
Examples like these provide the basis of the claim made earlier that this banjo formant appears to have higher perceptual salience than individual modes.
This hypothesis deserves to be tested in a formal psychoacoustical study. Figure 13 a Admittances calculated from the rectangular membrane model, resulting from varying head size by factors 0. The final set of demonstrations, Sounds H. Weighted mixtures of the measured admittance and the simulated admittance from the rectangular model were computed, and the crossover frequency between them was varied so that the formant could either be excluded or included.
Certain of the sound examples exhibit a phenomenon that strikes many listeners as unrealistic. Now David Politzer, who won the Nobel prize for physics in , has worked out the answer. He says the noise is the result of two different kinds of vibrations. First there is the vibration of the string, producing a certain note. However, the drum also vibrates and this pushes the bridge back and forth causing the string to stretch and relax. This modulates the frequency of the note.
When frequency of this modulation is below about 20 hertz, it creates a warbling effect. Guitar players can do the same thing by pushing a string back and forth after it is plucked.
But when the modulating frequency is higher, the ear experiences it as a kind of metallic crash. And it is this that gives the banjo its characteristic twang. If you're in any doubt, try replacing the drum membrane with a piece of wood and the twang goes away.
That's because the wood is stiffer and so does not vibrate to the same extent. Interesting what Nobel prize-winning physicists do in their spare time. This discussion has been archived. No new comments can be posted.
Full Abbreviated Hidden. More Login. Keb' Mo' with banjo picks on guitar is something Score: 2. Re: Score: 2 , Interesting. Re: Score: 3. Re: Score: 2. Now you have found me Score: 1. You just can't sing a depressing song when you're playing the banjo. You can't go-- "Oh, murder and death and grief and sorrow!
Share twitter facebook. Re: what a Happy instrument Score: 3. Think most folks here and geeks in general would recognize this one - The Eagles-Journey of the Sorcerer [youtube. Of course you can Score: 2. That's what all the weird minor keys and modes are for.
The real secret Score: 4 , Informative. The drum membrane is made out of 'possum skin. This sure looks like a candidate for an IgNobel? Parent Share twitter facebook. Does it need to be written down? It wasn't like the banjo was accidentally made That is why there are all sorts of hybrid instruments, like the Dulcijo dulcimer banjo , where the whole body is designed to be just like a normal dulcimer except for the bridge, which sits atop a tiny drum head like a banjo does.
It is neat he did math behind it, but the summary makes claims about how mysterious it was, and that sounds pretty ridiculous.
Re: Score: 1. Just because the guy is a Nobel peace p. Score: 5 , Interesting. Re: Score: 2 , Informative. Re:dont need to replace the drumhead Score: 5 , Insightful. What about the Nobel prize-winning biologists? Score: 4 , Funny. Ig Noble Score: 2. I think he's just going for the Ig Noble prize.
Playing a banjo is like an exercise in physics. By definition, physics is the science of matter and energy and the interactions between the two. From this we can see how this fits naturally into what we are doing when we play a banjo. We will be walking through the pathway that the vibration passes to give us the resulting sound that we hear when we play.
By looking at the pathway, we can understand how the materials themselves can regulate the sound we hear out of the banjo. It is generally accepted that the first banjos were constructed without a tone ring. They were built with a round rim made of wood with a skin head just like Changing your banjo strings is one of the easiest and best ways to bring the tone of your banjo back to life.
One of the most common questions we hear is how Learn how to properly adjust the action of your banjo via the coordinator rods. This is the rebroadcast of the 8th episode of our series Deering Tech Live. In this week's episode, something a little different. Greg Deering, the cofounder Your Deering. The strings are connected to both the neck and the bridge.
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