The sound of any type of guitar (and especially acoustic ones) is influenced by many factors - the size of the instrument, its shape, the fastening of the springs, and even such seemingly insignificant things as the weight of the neck and tailpiece. But the main thing is the tree.

All guitars sound different and one of the main reasons for this phenomenon is the difference in the types of wood from which they are made.

Top deck

Let's start with the main thing: the top deck. This is the part of the instrument that most influences the sound. There are two standard types of wood used for the top - these are spruce (spruce) And cedar (cedar). As a rule, spruce gives the sound a sharper and more sonorous tone, while cedar is softer and more “enveloping.” Acoustic guitars mainly use a type of spruce called "Sitka spruce". It grows both in America and Europe, and is not a rare breed, which is why its prices are moderate. Sometimes on the tops of more expensive instruments you can see "Engelmann spruce", this species is also called "German spruce" or Engelmann spruce. It grows mainly in the Alps and Canada. It is softer than ordinary spruce and, accordingly, its sound is not so sharp. It also looks different from ordinary spruce - it has a white tint, almost milky color. This is especially noticeable on older instruments, where sitka becomes golden in color and engelmann becomes slightly yellowish.

In very rare cases and, as a rule, on instruments costing over $3000, you can see another subspecies of spruce - "Adirondack spruce" — "red spruce". This is a rather rare and expensive variety, with a sonorous sound like sitka, but deeper. This species of spruce was once considered the standard in guitar making, but for many years the vast majority of guitars have been made from "sitka spruce". Hence the conclusion - the most popular types of wood for the front wall are spruce or cedar. Cedar gives the sound a softer shade, but spruce is more sonorous. In addition, spruce acquires a deeper sound over the years; it's like good cognac - the older it is, the better. Cedar practically lacks this quality. But there are exceptions to any rule - sometimes you come across nice-sounding and quite expensive instruments, where the entire body (top, bottom, and sides) is made of mahogany or koa wood, but these are exceptions. The vast majority of guitars are still made with a spruce or cedar top. Cedar is especially popular in classical guitars.

Shell and back

Let's move on to the shell and bottom deck of the body. They are usually made from the same materials. Most popular - "Mahogany" (mahogany/mahogany/mahogany), "Rosewood" (rosewood) And "Maple"(maple). Not everything that is good for electric guitars is good for “acoustics”; for example, alder and linden are practically not used. The standard is considered to be mahogany and rosewood. All other materials are usually compared with them.

Mahogany gives the instrument a soft, “even” sound. This sound is usually of medium depth and each string sounds well separately, that is, mahogany is an excellent choice for those who like to play “plucking”. Also, when using amplification (sound reinforcement) systems, this type of wood gives excellent results - especially if the instrument does not have an internal pickup and you have to record into a regular microphone.

Rosewood, on the other hand, has a deeper and more “viscous” sound - this is especially felt in the bass. This type of wood is good for rhythm parts, playing in an acoustic orchestra, and simply if you like a deeper sound. Unlike mahogany, individual strings are less audible, but if you sharply strike all the strings at once, you get a complex and voluminous sound. These guitars are a little more difficult to record into a microphone, but if the electronics are built into the guitar, the results will be good.

All other species are compared to these two. For example, maple has a sharper and more sonorous sound than rosewood, that is, closer to mahogany, but it does not have the same melody and softness of sound as mahogany.

Another fairly well-known tree in guitar building is nut. Its sound is quite sonorous and not very deep, but if you combine it with cedar, you get excellent results.

Also in lately gaining popularity Hawaiian koa. Its sound is soft and quite deep, but there is no ringing in it. But outwardly it is one of the most beautiful views tree.

In conclusion, it must be added that the most “elite” wood in acoustics is considered Brazilian rosewood. Until 1969, almost everyone used it in guitar making, but the Brazilian government banned its export and now for two good dry boards for the sides of a guitar you have to pay up to $2000, which few can afford. Therefore, most modern guitars are made from rosewood exported from other regions. It should be noted that the acoustic properties of a particular tree change depending on where the tree grew. This list could be continued, but it is impossible to list everything, and we have considered almost all the main varieties found in “acoustics”. The rest can be called the exception rather than the rule.

Fingerboard and neck; tailpiece (bridge)

What remains is the neck, fretboard and tailpiece. These elements have little effect on the sound. Necks are generally made from mahogany or (less commonly) maple. These are hard and relatively inexpensive breeds. Classical guitars often use cedar with a glued strip. ebony (ebony). Ebony is very hard and is also commonly used for fingerboards and tailpieces. But it is quite expensive, so if you do not have a master guitar, then most likely the pickguard and tailpiece on it will be made of rosewood. This is also not bad - rosewood is softer than ebony, but quite suitable. Only decorative details remain, such as sides, socket details and the like. Most often they are plastic. There are also wooden ones on expensive instruments, but they certainly do not affect the sound in any way.

It is believed that the type of wood from which the springs are made also gives color to the sound, but the shape and size of the springs themselves play a much larger role, and they are usually made of the same material as the top soundboard.

Most relatively inexpensive acoustic guitars are made not from solid wood, but from laminated wood, and it should be noted that lately laminated guitars have become increasingly better and better. best quality. Basically, the main thing is that the top is made of “real” wood, and everything else is less important. In laminated guitars, the influence of wood on the sound is much less - the pressed layers of wood do not vibrate as freely as a solid wooden plate, so these instruments have less “individuality”.

As a piece of advice: if you are looking for a guitar under $300, then don’t pay attention to the wood at all - the main thing to consider is the ease of play, the quality of the glue and, of course, the sound!

Another important point is the location of the fibers. Look closely at any decent acoustic guitar and you will see that both the front and back walls of the soundboard consist of two symmetrical halves. Moreover, not only the shape itself, but also the arrangement of the fibers is usually symmetrical. And the fibers themselves are also located evenly. This is achieved through a special wood cutting system. It is believed that this best way make the wood vibrate optimally. In addition, you need to pay attention to the distance between the fibers, especially on the front wall. Typically, the greater the distance, the softer the wood and, accordingly, the sound is softer and less sonorous. It is believed that best option, this is when the distance between the fibers is from 1mm to 2mm over the entire surface. In addition, it is good when this distance does not change much from the center of the front wall to its edges. In other words, even and parallel fibers allow wood to vibrate most freely, and, therefore, give us a good and beautiful sound!

Chapter 3. String and top

3.1 Guitar body as an amplifier

In the previous chapter we showed that many of the techniques for producing different sounds on a guitar can be learned by looking at an isolated string. But the string itself is a very weak source of sound. I got to play a "guitar" made to demonstrate this fact: this guitar had a neck, nut, bridge and pegs... everything except the body, instead all the parts of the guitar were mounted on a solid block of wood. The sound of this “bodyless” guitar was very weak and thin, bass sounds were completely absent.

There are two reasons why a string... is a very weak source of sound. Firstly, it has a relatively small surface area and therefore cannot cause large air disturbances. Secondly, any compression wave coming from one side of the string is effectively canceled out by a wave reflected from the opposite side, since the diameter of the string is very small compared to the wavelength, especially at low frequencies. (Wavelength... is the distance that travels sound wave during one cycle. Since the speed of sound in air at room temperature is 344 meters per second, the wavelength at the frequency of the lower note E (82.4 Hz) is 4.17 meters; at the frequency of upper C (988 Hz) it is equal to 34.8 centimeters.) Each of these two reasons indicates that a larger vibrator is needed for more effective sound emission.

For this purpose, a guitar body is used, which acts as an acoustic amplifier. To some extent, it is desirable that, similar to an electric amplifier or loudspeaker, the cabinet should have a "flat" (even) response across the guitar's frequency range (roughly 70 to 10,000 Hz). However, as we will see in this chapter, this ideal cannot be approached in practice. Each guitar has its own, more or less widely varying frequency response, sometimes called formant response, and therefore each guitar colors the sound in its own special way. The art of the instrument maker (guitar making still owes very little to science) consists in using the materials at his disposal in such a way as to obtain the special sound he envisions.

In the following sections, we will try to gain a basic understanding of how the body of a guitar works as an amplifier, sensing the vibrations of the strings and emitting them as sound. It will not be necessary to consider the matter in as much detail as in the case of the vibrating string, since the characteristics of individual guitars are not our primary interest. Our main concern will be to consider how the player can best extract the sound from the instrument, and a brief general study will suffice for an answer that will apply to any guitar of standard design.

3.2 Role of the upper deck

All parts of a guitar's body contribute to the sound, but they are by no means equal in importance. The reader can check this very easily as follows:

Experiment 1: Pluck all open strings (to produce a rich mixture of overtones over a wide frequency range) and use your palms to dampen (a) the shell, (b) the back, and (c) the top.

In case (a), very small vibrations are felt, and it is almost impossible to muffle the sound. On the lower deck, case (b), vibrations are felt more strongly, but the degree of influence on the sound still remains small. But in case (c) the muting effect is very strong, especially if you put your palms on the area around the stand. (At this point you can make a funny "wah-wah" sound by alternately raising and returning your palms.)

The extreme importance of the top is not at all surprising, since the strings are connected to it almost directly. If the soundboard is capable of receiving string vibrations, then it, in turn, will be able to excite the rest of the body of the guitar, as well as directly emit sound. If this is not so, then there is no sound; it is lost, as they say, at the very first fence. IN English The top soundboard is called the “soundboard”, emphasizing its vital role in converting string vibrations into sound. However, this second experiment will force you to abandon the idea that the top is the only important vibrator in the guitar body.

Experiment 2. Place the guitar on a horizontal plane with the strings up and cover the socket with some flat object that will not rattle or interfere with the vibrations of the strings (I use a soft leather disc). Start playing notes throughout the guitar's range and notice the difference in sound caused by the closed rosette. It can be seen that the response in the area high frequencies remained virtually unchanged, but all bass notes (on my guitar...roughly below open D) suffered a noticeable loss of "thickness." The sound in general became relatively weak and nasal.

Closing the outlet has two effects. The first... is the cutting off of sound reflected from the internal walls, especially the lower soundboard, and the second... is the neutralization of the action of the second most important sound source after the upper soundboard itself. This is the volume of air trapped within the body of the guitar, which oscillates like a pump... air is alternately pushed out and pulled in through the socket. Of course, usually only a small amount of air is moved in this way, but in the region of the main air resonance frequency, air vibrations can be directly felt (if the guitar has a good bass response) if you place your hand near a socket. This resonant peak is typically observed at a frequency of about 100 Hz (around the low G on the sixth string), but this frequency varies depending on the volume of the body, the elasticity of its walls and the size of the rosette1. The main air resonance imparts a certain "boom" to notes whose frequencies are located in its vicinity, and enhances the overall bass response.

Thus, in the low-frequency region, the main sound comes not from the top deck itself, but from the air inside the case. However, the air is primarily excited by the response of the top deck. Here, as throughout virtually the entire range of the instrument, the top acts as the necessary first link in transmitting string vibrations to the listener's ear. With this in mind, we can ask whether there is any special way to make the string vibrate in such a way as to most effectively drive the soundboard. But before we get into that, we need to know some details about how the top itself vibrates.

3.3 Vibration modes of the upper deck

The top is essentially a slab of wood so light and thin (sometimes as little as 2mm thick) that it would not be able to support the tension of the strings unless it was supported by several wooden spacers (or struts) glued to its inside. , and a stand glued to the outside. The most active part of the top is its wider part, approximately in the center of which is the bridge. A major design challenge for guitars is placing the headplate bracing in such a way as to give it the necessary strength but still allow the area around the bridge to vibrate freely.

From an acoustic point of view, the record, spacers and stand together form one vibrator. We previously showed, in sections 2.2 and 2.4, that a stretched string (essentially... a one-dimensional vibrator) has a number of resonant frequencies that depend on the length, mass and tension of the string. By analogy, a plate also has resonant frequencies, which depend on its size and shape (in two dimensions), its mass and rigidity. The bracing and bridge add both mass and stiffness to the areas of the record to which they are attached, so changes in the bracing system can result in very noticeable changes in the response of the top.

Just like a string, each resonant frequency of the soundboard corresponds to a specific vibration mode. In Fig. Figure 3.1 shows the first thirteen vibration modes of the top of a guitar, the shape of the bracing of which is also shown. These photographs were taken by Dr Ian Firth from the University of St. Andrews using the latest laser technique of time-averaged interference holography2. In each case, the top deck was forced to oscillate at a single frequency, and the light and dark areas can be thought of as contour lines showing the top deck motions for a given vibration mode. (The movements between two adjacent dark regions are on the order of a millionth of a millimeter, which gives us an idea of ​​the sensitivity of this technique.) Form 1 has a frequency of 148 Hz and one region of strong excitation centered on the stand; Form 2 has a frequency of 236 Hz and two regions of strong excitation, on each side of the stand. That is, when the top deck oscillates in Form 1, the bridge area moves in and out perpendicular to the plane of the deck. In form 2, the stand swings relative to its middle, one side moves inward, the other at the same time ... outward.

It is not difficult to see the parallel that exists between these two forms and the first two forms of string vibration (see Fig. 2.1). The single region of strong excitation corresponds to the single loop of the first string shape; and, just as the second form of the string contains two loops and one knot, the second form of the soundboard contains two regions of strong excitation and one nodal line along which no vibration occurs, approximately coinciding with the line along which the two halves of the top soundboard are connected. We can approximately say that this correspondence is maintained for higher resonant frequencies: just like a string, the upper soundboard vibrates in ever smaller areas, while areas of strong excitation are separated by nodal lines. However, there are several significant differences.

Rice. 3.1 Vibration modes of the upper deck

In both cases, the vibrations are transverse, that is, the string moves in a direction perpendicular to its axis, and the upper soundboard ... perpendicular to its plane. But the string has two degrees of freedom for transverse vibrations, and the top soundboard... only one. In other words... the top can only vibrate perpendicular to its plane, but the string can vibrate parallel or perpendicular to the top, or in any direction in between. For now we are simply mentioning this general principle, but in the remainder of the book we will deal mainly with the implications of this fact for the guitarist.

Another difference can be seen if we compare the frequencies of the string vibration modes (Figs. 2.1 and 2.2) with the frequencies of the soundboard modes shown in Fig. 3.1. All modes of string vibration have frequencies that are integer multiples of the fundamental frequency, and therefore the string produces a musical sound with a clearly definable pitch. The frequencies of the top shapes, with rare exceptions (for example, shapes 9 and 10 of the top in question have frequencies of 770 Hz and 880 Hz, respectively), are not harmonically related to each other, and therefore if the top is struck, a specific note will not be produced. This is actually a good thing, since the response of the top, whose resonant frequencies will be harmonically related, will vary very dramatically from note to note. Even so, the resonant frequencies of the top will result in more or less pronounced changes in volume and quality for different notes, since any overtone of a note that has a frequency close to the resonant frequency of the top will be amplified. For example, you might expect that the top deck shown in Fig. 3.1 will respond strongly to the open D string (147 Hz), not only because the fundamental frequency of this note is close to the frequency of the first mode of the treble, but also because its sixth, seventh and tenth overtones lie quite close to the forms of the treble. decks numbered 10, 11 and 13, respectively. Another strong note would be the open A string (110 Hz), the third, fourth, seventh, eighth and thirteenth overtones lie close to resonant frequencies top soundboard, in addition to the fact that its fundamental frequency will most likely coincide with the main air resonance. On the other hand, a B flat note on the third string (233 Hz) is unlikely to sound strong; Although its fundamental frequency is almost identical to that of the second soundboard mode, none of the higher overtones coincide with the resonance frequencies.

These examples explain why the presence of resonance frequencies does not prevent a guitar body from working quite well as a wide-range amplifier. Each note on a guitar has several overtones that lie fairly close to the resonances. In addition, the internal damping of the top deck prevents vibrations from gaining a very large amplitude, even at the resonance frequency. (Notice how different this is from the case where a string starts to respond quite strongly if some other string vibrates at a frequency that matches one of the first string's natural frequencies... this resonance effect contributes significantly to the richness of a guitar's tone, but it can also causing problems when trying to produce a clean melodic line.) That is, damping the top is somewhat useful because it evens out the response, albeit at the expense of power. This is one of the reasons why it is very difficult to make a guitar that will sound loud and even throughout its entire range. The other two characteristics of a guitar that conflict with each other... are volume and sustain, since at resonance the top will absorb the energy from the string relatively quickly. All of the above confirms the statement that no guitar body can come close to the ideal of a good audio amplifier. The tool maker always has to make a compromise between various conflicting factors.

In Fig. Figure 3.2 shows the top frequency response measured by Bernard Richardson of University College, Cardiff, using a guitar of his own design. The guitar was placed in a room with heavily padded walls to avoid sound reflection, and was driven by a vibrator mounted at the edge of the soundboard, diagonally down from the bridge. Using a microphone, the sound intensity was measured when the exciting frequency changed from 20 to 20,000 Hz3. You can notice that below 80 Hz and above 6000 Hz the response is very weak. The first peak, at a frequency of 95 Hz, is caused by the main air resonance, and the next two, at frequencies of 154 Hz and 216 Hz... are caused by the first and second vibration modes of the top soundboard, respectively. The extent of the influence of these, and the more densely spaced higher peaks, can be appreciated by looking at the wide range over which the response varies between peaks and troughs. The 30 dB response changes we see here would be catastrophic for an amplifier or speaker, but they are integral to the sound of a guitar. It's no wonder that the frequency, height and slope of each resonant peak determines the sound of any individual guitar so much, and that because of this, no two guitars will sound exactly the same.

Rice. 3.2 Frequency response of the top deck

The main function of the soundboard, of course, is to respond to string vibrations at frequencies corresponding to the string's vibration modes. However, striking the soundboard will cause it to vibrate the sum of its own modes, in much the same way that plucking excites the vibration modes of a string. This sound is not very long lasting due to the heavy damping, and as we have already noted, it does not have a clear pitch because the frequencies of the modes are not harmonically related. However, striking the top near the bridge (a light strike, preferably with a knuckle rather than a fingernail, with the strings muted) will produce a rich sound in which the height of the main air resonance can usually be recognized. If you close the socket, the air resonance will disappear, and the pitch of the sound will seem to increase. Even higher pitched sounds are produced by plucking the top closer to the edge, for the same reason as with strings... higher pitches are more excited when plucked near one end (see sections 2.6 and 2.7). The principle of gradual string release introduced in section 2.8(b) also has its relevance here: a soft object whose impact is spread over a relatively long period of time suppresses higher frequencies and produces a dull sound, while a harder object whose impact is sharper will produce a dull sound. emphasizes the highest forms, causing a sonorous knock.

The fact that the sound changes depending on where and how the body of the guitar is struck is, of course, well known to players who use it to achieve many different percussion effects. Less obvious, but nonetheless significant, is the fact that any note played on a guitar has some kind of percussive element, which we'll look at in section 3.5. For now, let's turn our attention to the main topic of this chapter: the ways in which energy is transferred to the top soundboard from the vibrating string.

3.4 Connection of string and top soundboard

When two vibrators, each with its own set of natural frequencies, are connected, the composite system behaves in a very complex manner, which depends on the properties of each vibrator and the nature of the connection. Guitar string and the upper deck form one of these oscillatory systems, and the details of their interaction are still very far from being fully understood. But in one respect their interaction is very simple.

The guitar's bridge, which is glued to the top and, from an acoustic point of view, behaves as a single unit with it, merely defines one of the ends of the vibrating string (at the bone) and serves to secure the string. Therefore, as a first approximation, we can consider that the strings are attached directly to the top soundboard. In this case, any force acting on the string will tend to move the top soundboard in the same direction. That is, if the string is pulled down towards the soundboard, then the upper soundboard will move down a little; if the string is pulled up, the top soundboard will also move up a little. Therefore, the continuous up and down movement of the string will cause a corresponding movement of the top area near the bridge.

In principle, the same applies to movements of the string in a plane parallel to the top soundboard, which will tend to move the soundboard in that direction. However, as we showed in the previous section, the top deck can only oscillate perpendicular to its plane. Thus, the most obvious way to make the soundboard vibrate in transverse patterns is to force the string to vibrate perpendicular to the soundboard.

Perhaps this statement is quite difficult to accept in this form. Among other things, this recommendation is almost impossible to follow, since getting the strings to vibrate exactly perpendicular to the top would require a very awkward hand position. It also contradicts the generally accepted teaching that many guitarists follow without question, which is that the only reasonable direction in which the string should vibrate... is parallel to the soundboard4. As for the second idea, there is enough evidence below to completely refute it. But the first objection is not without foundation. Indeed, it is impractical to limit the string's vibrations to just the vertical plane, but at any given time the vibrations will contain components both parallel and perpendicular to the soundboard. Even if the performer intended for the string to vibrate horizontally, he will likely also produce noticeable perpendicular vibrations. It is this component that directly sets the top deck in motion, and it is practically irrelevant whether the accompanying horizontal vibrations have a large or small amplitude. By the way, it also doesn't matter whether these components are in phase, so that some point on the string moves in a straight line, or out of phase, so that this point describes an ellipse.

However, the previous description was, to put it mildly, greatly simplified, since direct tension and repulsion are not the only way that a string can cause various forms of vibration in the top. Since the force from the string is applied to the bone, which is located at some distance from the top soundboard, parallel vibrations of the string will cause a slight rocking of the bridge, which causes, for example, the second form of vibration. (In this regard, it will be interesting to compare a guitar stand with a high bow stand string instruments. The latter is specially designed to produce such a swing, from one foot of the stand to another, when the bow is drawn along the string almost parallel to the top soundboard.) You also need to take into account that additional stretching of the string during vibrations causes changes in tension, which causes, for example, the third mode of vibration . These changes occur at twice the frequency of the string's vibrations, since the tension increases regardless of which direction the string is deflected. But the reader should not delve further into these additional connection mechanisms, since on the guitar their contribution is relatively minor5. Let's get back to more practical issues by doing a simple experiment.

Experiment 3. Try to make the open fifth string vibrate as near (a) parallel, (b) perpendicular to the soundboard as possible. This is not very easy to do, and to achieve this it is practically useless to pluck the string in the usual way, pointing the tip of your finger or nail towards the next string or down towards the soundboard. (The reasons why this is so will be shown in the next chapter, which will deal more fully with the plucking process.) The best method I have found is to grasp the string between the thumb and forefinger and pull it back like a bowstring in the desired direction, then the string is released. In case (a) it may be necessary to pass your finger under the strings, as shown in Fig. 3.3(a). In case (b) the string is pulled back as shown in Fig. 3.3(b) and is released towards the top deck, while it is necessary to limit the amplitude so that there is no impact on the frets. (In normal guitar playing, this limitation does not apply as strictly, as will also be explained in the next chapter.)

Rice. 3.3 Experiment 3

With a little practice, visually tracking the vibrations of the string after release, you can make the string vibrate almost exactly in the desired plane. The result is worth the effort as it is very impressive. The more accurately the string vibrates in a parallel plane, the more the sound becomes like a faint hum. In contrast, vibration in the vertical plane produces a deep, powerful sound and a very noticeable response from the body of the guitar.

The open A string was chosen for this experiment because its fundamental frequency is close enough to the main air resonance of most guitars and therefore produces the most striking contrast. But almost the same thing happens if you choose any other open string.

Experiment 4. Repeat the previous experiment sequentially for all open strings in turn, this time listening to each note until it fades. The difference in density and loudness is present in each case, but it is only noticeable at the beginning of the note. Towards the end, the difference in sounds played parallel or perpendicular to the top will practically disappear. This shows that over time, the polarization of string vibrations (that is, the ratio of the amplitudes of the perpendicular and parallel components) changes. In addition, you can notice that while the sound of parallel vibrations on bass strings is simply quieter, on treble strings the difference from perpendicular vibrations is noticeable not only in the volume of the sound, but also in its qualities. If we consider the first string, although the sound of parallel vibrations lacks the “density” of the sound of perpendicular ones, it nevertheless sounds almost as bright. This shows that the direction of vibration of the string is less important at higher frequencies.

Let's look at this idea in more detail by conducting the same experiment at the highest possible frequency. We learned in Section 2.11 that they can be excited by plucking the first string just under one inch from the bridge. If the plucking point is located at a distance of, for example, one-thirtieth of the length of the string, then the vibration modes around the fifteenth are more strongly excited, with frequencies of about 5,000 Hz.

Experiment 5. Repeat the previous experiment on the first string close to the bridge. This time it will be difficult to see in which direction the string is swinging and you will need to rely on the feel of the bowstring technique. It will be no less difficult to ensure the same amplitude in both cases, which, of course, is extremely important for a correct comparison. However, I tried this experiment on several guitars and in all cases I got results similar to the following.

Perpendicular vibrations produce a generally louder sound, with a clear "thump" at the beginning of the note; with parallel vibrations this noise was absent, and the note sounded very thin, although with subjectively the same brightness as with perpendicular vibrations.

Although this would seem to confirm the idea expressed earlier, it must be admitted that an “experiment” that is so difficult to control and which relies so heavily on subjective impressions is not worthy of the name. Given the need for a well-controlled experiment, I was very fortunate in being able to take advantage of the work of Bernard Richardson, who at University College, Cardiff, had developed an ingenious apparatus for just this purpose. The essence of the Richardson method is that the string is automatically plucked using a cotton thread, which allows you to control not only the direction of plucking, but also precisely set the point at which plucking is performed and the plucking force. The sound of the resulting note was recorded in a soundproof room, and the recording was analyzed by playing it through a filter connected to a recorder, providing a visual representation of the first few overtones of the note. Or one could plot the intensity of sound in each octave of the frequency range.

Using guitars of his own making, Richardson received large number such recordings, and they left no doubt that in the low and mid-frequency ranges (below about 1500 Hz) perpendicular plucking produces significantly greater sound intensity than parallel plucking. (Physicists, for example, may be interested in the fact that the height of the peaks on the open first string is usually about 10 dB.) In addition, when plucked perpendicularly, the peaks are much steeper, the sound intensity very quickly reaches its maximum value, and then falls instantly; and with parallel plucking, it may take a significant fraction of a second for the sound to reach peak intensity, after which the decay is usually similar to that after perpendicular plucking.

This is all consistent with the hypothesis that the string vibrations gradually lose their original polarization, but at lower frequencies the soundboard is directly driven only by the perpendicular component.

At frequencies above approximately 1,500 Hz, there is practically no difference between the two plucking directions. From the experimental results that were provided to me, it can be assumed that some of the higher overtones are more excited by parallel plucking, and the rest... by perpendicular plucking. It seems that the initial direction of vibration of the string is not as important at higher frequencies as at lower frequencies. This is most likely due to the fact that a significant part of the sound emitted at the highest frequencies does not come from the body of the guitar at all, but directly from the strings. (For example, at a frequency of 5,000 Hz, the air wavelength is only 6.9 cm; in comparison, the diameter of the string is still small, but not so small that it can be neglected.) One confirmation of this is the fact that although the “frameless The guitar mentioned at the beginning of this chapter sounded quite pathetic and weak in the lower frequencies, when played very close to the bridge almost came close to my Ramirez guitar.

Regardless of the reason, this provides the ability to dampen sounds in the bass and midrange without losing high frequencies by causing the string to vibrate parallel to the soundboard. We'll see in the next section why this can sometimes be useful. However, deliberately causing the string to vibrate parallel to the soundboard should be the exception and not the rule. If a tight sound is desired, it is best for the guitarist to concentrate on the perpendicular component and ignore the parallel component.

If it seems to you that this turns a familiar rule upside down, and this is indeed the case, then you should not jump to conclusions that everything that follows from this rule is also wrong. To be precise, the idea that the string should always vibrate parallel to the soundboard was the reason why apoyando (supported plucking) and tirando (unsupported plucking) should be performed as equally as possible, from the same position of the hand, and that with tirando, the nail should pass as close as possible to the next string without touching it6. This is actually sound advice, but it only happened because in this case two theoretical errors added up to correct practical advice. This confusion arose from a misunderstanding of the nature of the pinching movement, as we will see in the next chapter.

3.5 Start transition

Section 1.5 stated that a non-musical sound heard at the beginning of a note is important characteristic any instrument, and the origin of this starting transition was briefly described. We now know enough about the behavior of the two parties involved...the strings and the top...to learn a little more about this phenomenon. As we proceed, we will take the opportunity to draw on several ideas from the first three chapters to provide a fitting conclusion to this largely theoretical part of the book.

Consider a string pulled diagonally down toward the soundboard just before it is released. As we learned in Section 2.6, in fact the string in at the moment held in readiness to oscillate according to the sum of forms corresponding to its deformed form. But in the previous section we learned that any force applied to the string will act in the same direction on the soundboard. Of course, the deck will be essentially stationary in the parallel plane, but the perpendicular component of the force will cause slight deformation of the top deck. In this way, the upper soundboard is also kept in readiness to oscillate by the sum of its shapes corresponding to this deformation.

When the string is released, the soundboard is also released from its deformed state, and two vibrations occur simultaneously: the vibration of the string with its harmonic modes, and the vibration of the soundboard, the frequencies of which modes do not usually correlate harmoniously with each other or with the frequencies of the string modes. Therefore, this second vibration is a noise that is clearly distinguishable from the musical sound of the note, but decays quickly due to the strong damping of the soundboard...hence it is called the "start transition". At this time, the string continues to vibrate and transmits its vibrations to the upper soundboard. That is, the musical sound produced by the string is heard from the very beginning and continues to sound for a long time after the end of the starting transition, provided that nothing interferes with the vibrations of the string.

The reader may have already noticed the similarity between this description of the start transition and the sounds that occur when hitting the top deck, described in Section 3.3. Indeed, the two sounds have much in common: releasing a string has almost the same immediate effect on the top as lightly hitting the bridge. The pulse in the bridge area, as described earlier, emphasizes the low-frequency vibration modes of the top soundboard, in particular... the main air resonance. Therefore, the start transition usually sounds like a faint thud at the beginning of the note. The nature of the start transition, as well as the musical quality of the note, depends on the manner in which the sound was struck. The sharper the release, the sharper the impulse on the stand will be, and the more the transition will be like a "knock" or "click". In addition, the transition is very sensitive to the direction of plucking, since it is excited mainly by the perpendicular component of the tension of the string before it is released. If the string is made to vibrate parallel to the soundboard, the low-frequency transition noise disappears, which can be easily verified using the following experiment.

Experiment 6: Mute the strings using a piece of soft cloth placed between the strings and the fingerboard. This will not dampen their vibrations completely, but will equalize their duration with the duration of vibrations of the upper deck. Now, no matter which string you pluck, it is easy to hear the “thump” of the top transition mixed with the short vibrations of the string. You can easily demonstrate the dominant role of the air response by closing the outlet. This will make the sound of the transition much quieter. Now compare the sound produced by either string when pulled (a) perpendicularly or (b) parallel to the soundboard, in the manner used in Experiment 3. The booming sound heard in case (a) disappears in case (b).

If the string is plucked perpendicular to the soundboard, with the same force, but at different points on the string, then you can hear that the transition becomes more and more significant as the plucking point approaches the bridge. (This is due to the simple fact that more and more of the plucking force is transferred to the top rather than the saddle.) But in Section 2.7 (Fig. 2.6) we showed that the same force produces vibrations of less energy as it approaches the bridge . In other words, when plucking near the bridge we get more noise and less musical sound.

The percussive sound produced near the bridge can sometimes be used to amazing effect, but it can also be a great disturbance, for example when playing high harmonics on treble strings. In Section 2.10 we showed that to make the fifth harmonic sound clear, the string must be plucked about three inches (7.62 centimeters) from the bridge; but if, when plucking, a strong perpendicular component is introduced, then the noise of the transition will immediately almost completely drown out the gentle sound of the harmonic. Let's take into account that on the first string, the harmonic on the fifth fret has vibration mode frequencies equal to 1319, 2637, 3956, 5274 Hz, and so on. Since all of them, except the first, lie in the high-frequency range, in which the sound is emitted almost equally well, regardless of whether the vibrations began parallel or perpendicular to the top soundboard, we will lose practically nothing, but will gain a lot by reducing the perpendicular component in this case fluctuations to a minimum. The same approach can be used if you need to get a thin and weak sound, in particular when playing treble strings near the bridge.

I hope you found this chapter to provide some useful background knowledge about how a guitar works. The main idea of ​​the chapter, which will be used in the part of the book devoted to sound production techniques, can be expressed very briefly. We now know that the direction the string vibrates has a significant effect on the quantity and quality of sound produced. It follows from this that the guitarist must master the technique of controlling the direction of release over the widest possible range. In particular, a normal plucking motion should introduce a noticeable perpendicular component to the vibrations since the top is driven primarily by it. These are the main goals, and we are now ready to discuss how they can be achieved in practice.