EP1182641A2 - Soundboard made with fibre composite - Google Patents

Abstract

Resonance plate comprises a core plate (1) and a fiber coating (2) made of long fibers and arranged on both outer sides of the core plate. The core plate has a recess (3) surrounded by the material regions of the core plate where the total volume of the recess is not more than 80%, preferably 20-45%, of the total volume of the core plate. Preferred Features: Single regions of the core plate have different thicknesses.

Description

The invention relates to a resonance board in fiber composite construction, containing at least one of long fibers and carrier material existing fiber coating, for use for an acoustic Musical instrument, especially a string instrument.

The invention is described below using the example of the resonance plates of String instruments described in more detail. However, it is also for others with a sound box or sound board acoustic musical instruments (such as guitars and pianos) advantageous usable.

The resonance body of a string instrument is used by the two Soundboards (ceiling and floor) and the frames connecting them educated. The ceiling is traditionally made of spruce wood, the floor is mostly made of maple wood.

In recent times, people have already tried the sound boards Manufacture acoustic musical instruments in fiber composite construction. Structures in fiber composite construction mostly consist of long fibers, which are preferably oriented in certain directions, and one Carrier or matrix material, which is generally a thermosetting or thermoplastic.

Previous efforts to manufacture acoustic Musical instruments determined resonance plates in fiber composite construction consistently aim to improve the acoustic properties of the copying replacing wood if possible. Examples of this Experiments in the prior art known to date are given, for example, by DE 37 38 459 A1, EP 0 433 430 B1, US-A 5,895,872 and US-A 5,905,219. So DE 37 38 459 A1 strives for "a macroscopic heterogeneity almost identical to that of wood" and specifies that "that composite material similar properties to the spruce should have ".

These previously known resonance plates appear unsatisfactory in fiber composite construction that they are very acoustically good, solid wood soundboard made in traditional construction at most equivalent, but not at all are superior.

The invention is therefore based on the object of a resonance plate to create in fiber composite construction, which compared to award-winning, solid wood soundboard made in traditional construction a significantly improved acoustic quality has. The resonance plate according to the invention is intended in particular under Maintaining the familiar and desired timbre of a person Solid wood soundboard has a significantly higher sound power exhibit.

a) wenigstens ein aus der Resonanzplatte geschnittener Teststreifen weist einen Qualitätsquotienten (Q_M = c_L/rho) von mindestens 0,02 m⁴/sg, vorzugsweise von mindestens 0,04 m⁴/sg auf, wobei c_L die Schallgeschwindigkeit (in m/s) der Longitudinalwellen in Längsrichtung des Teststreifens und rho die mittlere Gesamtdichte (in g/m³) des Teststreifens ist;

b) der vom Umriß der Resonanzplatte umgrenzte Flächeninhalt der Resonanzplatte ist so groß gewählt, daß

b1) die Frequenz der Hauptkorpusresonanz (B1-Mode) von Streichinstrumenten in folgenden Bereichen liegt:

• bei der Violine zwischen 480 und 580 Hz, vorzugsweise zwischen 510 und 550 Hz,
• bei der Viola zwischen 380 und 500 Hz, vorzugsweise zwischen 420 und 460 Hz,
• beim Violoncello zwischen 150 und 210 Hz, vorzugsweise zwischen 170 und 190 Hz,
• beim Kontrabass zwischen 80 und 120 Hz, vorzugsweise zwischen 90 und 110Hz,

b2) die Frequenz der zweittiefsten Korpusresonanz (0,0-Mode) bei der Gitarre zwischen 180 und 240 Hz, vorzugsweise zwischen 190 und 220 Hz, liegt,

b3) die Frequenz der tiefsten Resonanz (0,0-Mode) des Klavier- bzw. Konzertflügelresonanzbodens zwischen 40 und 60 Hz, vorzugsweise zwischen 45 und 55 Hz, liegt.

This object is achieved according to the invention by combining the following features:

a) at least one test strip cut from the resonance plate has a quality quotient (Q _M = c _L / rho) of at least 0.02 m ⁴ / sg, preferably of at least 0.04 m ⁴ / sg, where c _{L is} the speed of sound (in m / s) of the longitudinal waves in the longitudinal direction of the test strip and rho is the mean total density (in g / m ³ ) of the test strip;

b) the area of the resonance plate delimited by the outline of the resonance plate is chosen so large that

b1) the frequency of the main body resonance (B1 mode) of string instruments lies in the following areas:

• in the violin between 480 and 580 Hz, preferably between 510 and 550 Hz,
• in the viola between 380 and 500 Hz, preferably between 420 and 460 Hz,
• in the cello between 150 and 210 Hz, preferably between 170 and 190 Hz,
• for double bass between 80 and 120 Hz, preferably between 90 and 110 Hz,

b2) the frequency of the second deepest body resonance (0.0 mode) in the guitar is between 180 and 240 Hz, preferably between 190 and 220 Hz,

b3) the frequency of the deepest resonance (0.0 mode) of the piano or concert grand resonance floor is between 40 and 60 Hz, preferably between 45 and 55 Hz.

In particular, the invention is based on the following considerations and To attempt:

If a test strip is cut from a resonance plate (as will be explained in detail in the description of an exemplary embodiment), the acoustic quality of this test strip can be assessed using a quality quotient Q _M , which is defined as follows: Q M = C L / rho

Here CL is the speed of sound (in m / s) of the longitudinal waves in the longitudinal direction of the test strip and rho the mean total density (in g / m ³ ) of the test strip.

The quality quotient Q _M is therefore higher, the greater the speed of sound of the longitudinal waves in relation to the vibrating mass. A large value of Q _M thus corresponds to a favorable mass-rigidity ratio of the resonance plate.

For spruce wood, a typical quality quotient Q _M = 0.0145 m ⁴ / sg results from C _L = 5800 m / s and rho = 400 kg / m ³ . The highest value achievable in spruce sound wood was measured in the tests on which the invention is based, QM = 0.016 m ⁴ / sg. This value corresponds to the values found on soundboards of the most famous violin makers (such as Antonio Stradivari). Below average spruce tone wood is Q _M = 0.012 m ⁴ / sg.

With test strips made of resonance plates in fiber composite construction, on the other hand, quality quotients Q _M of over 0.06 m ⁴ / sg can be determined. The acoustic material quality of soundboard in fiber composite construction is thus almost four times as high as the acoustic material quality of the best and long-aged spruce tone wood. Despite this well-known fact, it has so far not been possible to create resonance panels in fiber composite construction which, taking into account all the necessary aspects, are superior to solid wood resonance panels. The reasons for this difficulty and the sense of the combination of features according to the invention result from the following considerations.

If you manufacture a resonance plate with the same geometrical dimensions instead of wood in fiber composite construction, the much higher quality quotient Q _M results in much higher natural frequencies (resonance frequencies). This increase in natural frequencies leads to an undesirably sharp or nasal sound and thus adversely changes the timbres of the instrument.

One could think of lowering the natural frequencies of a resonance panel made of a fiber composite construction (and shifting it again in the direction of the natural frequencies of a conventional solid wood resonance panel) by making the resonance panel of fiber composite construction thinner than a corresponding solid wood resonance panel , In the experiments on which the invention is based, however, it was found that the quality quotient Q _{M of} a resonance board in fiber composite construction - in contrast to the quality quotient of a conventional solid wood resonance board - is thickness-dependent, namely that a reduction in the board thickness also a reduction in the quality quotient Q _M has the consequence. If you reduce the thickness of a resonance board in fiber composite construction (to lower the resonance frequencies back into the desired range), you also reduce the quality quotient Q _M and thus lose the acoustic advantage that the fiber composite construction itself has over traditional wood -Construction.

The invention therefore proceeds on the basis of these considerations a fundamentally different way to get the resonance frequencies of one in Fiber composite construction produced resonance plate in the desired area and familiar from solid wood soundboard lay.

In the solution according to the invention, the natural frequency increase caused by the fiber composite construction (with which the very desirable increase in the quality quotient Q _{M is} connected) is compensated for by such a geometry-related natural frequency decrease, by which the quality quotient Q _{M is} not significantly reduced. For this purpose, the surface area of the resonance plate is dimensioned larger than in the case of a resonance plate made of solid wood of a string instrument of the same timbre. An enlargement of the resonance plate results in a shift of the natural frequencies downwards. Because of its larger area, the resonance plate can then be given a correspondingly greater thickness without the natural frequencies leaving the range required for the desired and familiar timbre. The resulting quality quotient Q _M is thus significantly higher than that of a non-enlarged, thinner board in fiber composite construction.

Because an enlargement of the vibrating surface is also a Increase in sound radiation and thus an increase in acoustic efficiency of the instrument results in the solution according to the invention not only the desired timbre of classical string instruments, but it will be about it in addition also the others resulting from the sound radiation sonic properties, such as "carrying capacity", "volume" and "Dynamics", improved. The resonance plate according to the invention allows it with building instruments that respect listening habits (Tone color sensation) the conventional, made of solid wood Correspond to instruments, however with regard to their acoustic Efficiency significantly superior to traditional instruments are.

Would you be one with a sound box made of solid wood? conventional string instrument the area of the Enlarge resonance plates, so this would the natural frequencies of the Move the instruments down so much that a dull one ("potty") timbre results. With a conventional string instrument with solid wood sound boards would be a broadening due to the low transverse stiffness of the Solid wood panels also for the formation of vibration modes with narrow, lead parallel, antiphase antinodes that a low due to hydrodynamic short circuits Result in sound radiation (cf. Cremer, Lothar: "Physik der Violin ", Stuttgart 1981, p.341).

It is only then that the resonance plate is enlarged acoustically useful if a material (like a Fiber composite material) with a higher one than wood Flexural rigidity and therefore a higher speed of sound is used.

The acoustic condition formulated in feature b) of claim 1 serves to control comparable timbres. Characteristic b1) is the frequency of the main body resonance, which - according to the relevant literature - is referred to as B1 mode. Feature b2) specifies the second deepest body resonance for the guitar, which is designated 0.0 mode. Feature b3) relates to the deepest resonance of the soundboard of pianos or concert grand pianos, which is also designated 0.0 mode according to its mode of vibration.
The resonances mentioned, in particular their respective typical vibration form, are explained in more detail in the exemplary embodiments.

In the experiments on which the invention is based, Acoustics laboratory of the inventor modal analysis of excellent Instruments of famous violin makers (like Antonio Stradivari or Guarneri del Gesu). For violins whose timbres are from Artists and trained listeners as pleasant and balanced B1 mode is always in a relatively narrow range Frequency band between 510 and 550 Hz. A violin with a B1 mode tends to sound rough and well above this frequency range sharp while a violin with a B1 mode below this Frequency range tends to be dull and potty has. The natural frequency of the B1 mode can therefore be considered a reliable acoustic indicator for the timbre of a String instrument are considered.

Expedient embodiments of the invention result from the Dependent claims.

These and other details of the invention (such as extraction, Measurement and evaluation of test strips) are based on the drawing explained in more detail.

1 to 4 show the typical form of natural vibration of the main body resonance (B1 mode), as is the case with violins, violas, cellos and double basses. Parts of the literature also call the B1 mode C3 mode (Jansson) or B1 ₊ mode (Hutchins). The mode is determined with the help of experimental modal analysis. In experimental modal analysis, a large number of transfer functions (acceleration divided by force; or vibration response divided by vibration excitation) are measured by using a hammer (e.g. PCB 086C80) to excite the instrument at a number of coordinates distributed over the body. The vibration response is measured using an accelerometer (e.g. PCB 352B22) at the driving point. The upper end of the side edge (bass beam side) of the bridge is selected as the driving point. All of these measurements are carried out when the instrument is ready to play, with only the strings being dampened with foam in such a way that the steep-sided string resonances are damped, while the body resonances of the instrument to be determined are not changed. Apart from the piano or grand piano, which are measured in the normal standing position, the measurement of the other musical instruments in which the resonance plate according to the invention is installed is carried out with free-free storage. The instruments are expediently stored softly on foam cushions in the area of the upper and lower block. The transfer functions are evaluated using the relevant programs (eg STAR Structure) in the manner usual for modal analysis.

• in Längsrichtung des Bodens 2 verlaufen zwei Knotenlinien 3a und 3b, wobei die linke Knotenlinie 3a durch den Bereich des Stimmstocks 5 verläuft. Der Mittelbereich des Bodens 2 schwingt somit gegenphasig zu seinen beiden seitlichen Rändern. Für die B1-Mode ist diese Querbiegeschwingung des Bodens charakteristisch. Bei einigen wenigen Instrumenten kann beobachtet werden, daß die beiden Knotenlinien 3a und 3b sich im oberen Bereich des Bodens 2 bogenartig zusammenschließen.
• die (weiß gezeichnete) untere rechte Backe 4 der Decke 1 schwingt gegenphasig zu dem den größten Anteil der Deckenfläche einnehmenden (schwarz gezeichneten) Schwingungsbauch im Bereich des Baßbalkens 6, wobei die Knotenlinie 3c, welche diese gegenphasigen Schwingungsbäuche trennt, in der Regel durch den unmittelbaren Nahbereich des Stimmstocks 5, und anschließend durch das rechte (mit "f" bezeichnete) f-Loch verläuft, um den Deckenumriß im Bereich der größten Umrißbreite unten rechts zu verlassen.

1 shows the B1 mode of a violin by means of a contour plot, the left resonance plate representing the top 1 and the right resonance plate representing the bottom 2, in each case from the outside. The body is therefore shown "unfolded", although the measurement takes place in the assembled, ready-to-play state of the instrument. The black areas marked with "+" swing in phase opposition to the white areas marked with "-", whereby the black areas of the ceiling swing outwards together with the black areas of the floor (towards the outside of the body) and inwards after half an oscillation period , The same applies to the white areas of both plates. This phase relationship is shown in FIG. 2 on the basis of greatly exaggerated amplitudes (bold lines); it shows a cross section through the body on the line designated by A in FIG. 1. The thin lines reflect the rest of the body for orientation. The details of the amplitude distribution can vary from instrument to instrument; The following characteristics are typical for the mode of natural vibration of the B1 mode:

• Two knot lines 3a and 3b run in the longitudinal direction of the floor 2, the left knot line 3a running through the area of the tuning stick 5. The central region of the base 2 thus swings in phase opposition to its two lateral edges. This transverse bending vibration of the floor is characteristic of the B1 mode. With a few instruments it can be observed that the two node lines 3a and 3b join together in an arch-like manner in the upper region of the base 2.
• the lower right cheek 4 (shown in white) of the ceiling 1 swings in phase opposition to the antinode in the region of the bass bar 6, which occupies the largest portion of the ceiling area (black line), the node line 3c, which separates these antiphase antinodes, generally by the immediate one Close range of the reed block 5, and then runs through the right f-hole (labeled "f") to leave the ceiling outline in the area of the greatest outline width at the bottom right.

Fig. 3 (ceiling) and Fig. 4 (floor) show for better understanding also the natural mode of the B1 mode, but now (in Contrary to the contour plot Fig. 1) as a wire mesh model, with Fig. 3a and 4a the deflected with -90 °, Fig. 3c and Fig. 4c with + 90 ° deflected state compared to that in Fig. 3b and Fig. 4b show the idle state shown with 0 °.

The frequency responses shown in Fig. 5 to 8 represent the typical Input acellance of a violin (Fig. 5), a viola (Fig. 6), a cello (Fig. 7) and a double bass (Fig. 8). The input accuracy is that transfer function where the vibration excitation and the vibration response at the same Measuring point can be measured. The above-mentioned driving is the measuring point Point selected. It is the X axis of the input precision around the frequency, with the Y-axis around the vibration level (Acceleration divided by stimulating force) in dB. The Different resonances are clearly too individual peaks detect. In the violin and viola (Fig. 5 and 6) forms the B1-Mode typically the last outstanding resonance summit a body resonance region formed by the envelope 7. This resonance area is always due to a steep dip 8 (Anti-resonance) from the higher-frequency plate resonance peaks Cut. As can be seen in FIG. 7, the B1 mode forms the Violoncello usually has the highest low-frequency resonance peak below 300 Hz. The B1 mode is often without in the cello physical measurement methods due to the so-called Wolfston susceptibility of the bowed tone (especially on the C string) make out whose fundamental frequency is the resonance frequency of B1 mode equivalent.

In the double bass (Fig. 8), the B1 mode is usually second, the main body resonance in the area around the Helmholtz resonance Ao 100 Hz. The resonance peaks of the Helmholtz resonance Ao and the 4 to 7 are shown as T1 mode below the B1 mode marked such.

The second lowest mentioned in feature b2) of claim 1 Body resonance of the acoustic guitar is shown in FIG. 9 illustrated. This resonance is found in literature [see Fletcher N. H. and Rossing T.D: "The Physics of Musical Instruments", New York 1991] is referred to as fashion with a 0.0 character, since it has 9 knot lines neither in the longitudinal nor in the transverse direction of the ceiling, but rather rather by a single antinode per resonance plate (Ceiling and floor) is marked. The connection of cavity, The top and bottom of the guitar lead to three body resonances 0.0 characteristic, namely for the Helmholtz resonance and for two close in frequency, about 100 Hz above the Helmholtz resonance lying body resonances. In the feature b2) called fashion is the lower frequency of these two last-mentioned resonances, and thus since the Helmholtz resonance the The guitar's first body mode is the second lowest Body resonance, or the middle of the three body resonances with 0.0 character. It differs from the higher frequency, third Body resonance with 0.0 character due to the phase relationship between the ceiling and floor. Ceiling and floor vibrate in the feature b2) mentioned resonance in phase (in the same spatial direction), so that the body bends as a whole like a thick plate; in the higher-frequency, third 0-0 body mode, on the other hand, swing the ceiling and The floor is out of phase, thus causing the body to "breathe" out. The waveform of the mode mentioned in feature b2) is in 9 is illustrated by lines of equal amplitudes 10. These are centered around the area of the web 12 and describe one Antinode, which is about the shape of the lower outline of the Takes resonance plate [cf. Richardson, B.E. "The acoustical development of the guitar "in: Catgut Acoust. Soc. J. Vol. 2, No. 5 (Series II) May 1994; P. 5; Fig. 4b].

Feature b3) is the deepest resonance of the Soundboard of the piano or concert grand. This resonance will also with 0.0 mode according to their waveform designated. Their wave form is the same by lines Amplitudes 10 shown in Fig. 10 [see: Kindel: "Modal Analysis and finite element analysis of a piano soundboard "M.S. thesis, University of Cincinnati. Quoted from: Fletcher N.H. and Rossing T.D: "The Physics of Musical Instruments", New York 1998, p. 382].

The measurement of the quality quotient Q _M mentioned in claim 1, feature a) is expediently carried out as follows:

Strip elements 14 are cut out of the surface of the resonance plate. The proportions of a strip element are derived from the average thickness (D _m ) of the strip element as follows: the length L of the strip corresponds to 25 times the thickness D _m , the width B of the strip corresponds to 5 times the thickness D _m .

The speed of sound C _{L of} the longitudinal waves in the longitudinal direction of the strip element (strip) is then determined by measurement. The resonance method established in the field of structure-borne noise measurement is used for this measurement. It is illustrated in Fig. 11:

The strip 14 is elastically supported in the two node lines (n ₁ and n ₂ ) of its first natural bending frequency on elastic bands or foam wedges 15 (free-free boundary conditions). The strip is excited sinusoidally via airborne sound. For this purpose, a miniature loudspeaker 16, which is connected to a power amplifier 17, is positioned at a distance of approximately 5 mm below one of the two strip ends. The sinusoidal signal is generated by a sine generator 18. The oscillation response of the strip excited in this way is picked up with the aid of a sound level meter 19. For this purpose, the microphone 20 of the sound level meter is positioned at a distance of approximately 1 mm above the end of the strip opposite the loudspeaker. The frequency is gradually increased at the sine generator 18 until the natural frequency of the first natural bending vibration of the strip can be read off from the sound level meter by the associated maximum level of the level peak. (The slight natural frequency deviation due to the damping can be neglected here). The frequency f _{2; 0} (in Hz) corresponding to the maximum level of this resonance peak is noted. (Meaning of the indexing f _{n; m} : number of the nodal lines running in the transverse direction of the strip n = 2; number of the nodal lines in the longitudinal direction m = 0; the corresponding form of natural vibration is symbolized by means of the (dashed) lines of maximum deflection 21 in FIG. 11).

The speed of sound (c _L ) of the longitudinal waves (in m / s) is defined as follows: C L = (0.98 * f 2 0 * L 2 ) / D m

L is the stripe length (in m), D _{m is} the mean stripe thickness (in m), and f _{2; 0 is} the resonance frequency (in Hz). (If the strip thickness is not constant according to claim 5, the different thicknesses are averaged and an average strip thickness D _{m is} used.)

The average total density rho of the strip is calculated from rho = m / V. Here m is the total mass (in g) and V the total volume (in m ³ ) of the strip. The total volume V is determined by measuring the strip dimensions (strip length L (in m), strip width B (in m) and the average strip thickness D _m (in m)) in accordance with V = L * B * Dm.

12 shows the physically essential relationship on which the invention is based on the thickness dependency of the quality quotient QM: the strip thickness D _m (in mm) on the X axis and the quality quotient QM (in m ⁴ / sg) on the Y axis. applied. The curves labeled A (maple) and F (spruce) represent the quality quotient of the wood types conventionally used for soundboard. It is shown that it is independent of thickness and in this test series for spruce at 0.0155 m ⁴ / sg and for maple at 0.0067 m ⁴ / sg. The curve labeled VS shows the quality quotient Q _M for the test strips of the resonance plate according to the invention produced as a fiber composite sandwich. The deterioration of this quotient Q _M is clearly evident when the strip thickness is reduced to less than 4 mm. Depending on the material properties of the core plate and the fiber composite material (fiber basis weight; resin content, etc.), as well as depending on the core plate recesses and fiber coating (direction and density), different curves VS are obtained, i.e. different dependencies of the quality quotient QM on the plate thickness. According to claim 2, the thickness of the resonance plate is dimensioned such that the quality quotient Q _{M of} at least one test strip cut from the resonance plate has at least 90% of the maximum value achievable with the selected fiber composite material. This 90% line 28 is drawn in FIG. 12 for the fiber composite material on which it is based.

The function VS in FIG. 12 immediately reveals that a Compensation of the natural frequency increases of the resonance plate by Reducing their thickness to deteriorate the acoustic Quality leads. In contrast, according to the invention, the sound necessary natural frequency reduction by increasing the area bounded by the outline of the soundboard. The 13 and 14 show an embodiment for this. Because the width the resonance plate in the first approximation in the second power Inherent natural frequencies can be a relatively low one Widening of the outline 23 of the invention, with Fiber composite coating 24 built resonance plate by about 5% compared to the conventional outline 22 (shown in dashed lines) accomplish the required frequency shift.

The core plate 26 of the resonance plate has, as in FIG. 14, at one Segment shown, according to claim 4 recesses 27, wherein the Total volume of all recesses at most 80%, preferably between 20 and 45% of the total volume of material Core plate is. This feature allows an improvement of the Mass-stiffness ratio of the resonance plate. According to claim 5 has the segment of the resonance plate shown in FIG. 14 a different thickness D. According to claim 6, it has a multidirectional fiber coating based on not parallel arranged fibers 25 there.

Claims (6)

Resonance board in fiber composite construction, containing at least one fiber coating consisting of long fibers and carrier material, for use for an acoustic musical instrument, in particular a string instrument, characterized by the combination of the following features: a) at least one test strip cut from the resonance plate has a quality quotient (Q _M = c _L / rho) of at least 0.02 m ⁴ / sg, preferably of at least 0.04 m ⁴ / sg, where c _{L is} the speed of sound (in m / s) of the longitudinal waves in the longitudinal direction of the test strip and rho is the mean total density (in g / m ³ ) of the test strip; b) the area of the resonance plate delimited by the outline of the resonance plate is chosen so large that b1) the frequency of the main body resonance (B1 mode) of string instruments lies in the following areas: in the violin between 480 and 580 Hz, preferably between 510 and 550 Hz, in the viola between 380 and 500 Hz, preferably between 420 and 460 Hz, in the cello between 150 and 210 Hz, preferably between 170 and 190 Hz, for double bass between 80 and 120 Hz, preferably between 90 and 110 Hz, b2) the frequency of the second deepest body resonance (0.0 mode) in the guitar is between 180 and 240 Hz, preferably between 190 and 220 Hz, b3) the frequency of the deepest resonance (0.0 mode) of the piano or concert grand resonance floor is between 40 and 60 Hz, preferably between 45 and 55 Hz. Soundboard according to claim 1, characterized by such a thickness of the soundboard that for the given fiber composite material the quality quotient Q _{M of} at least one test strip cut from the soundboard has at least 90% of the maximum value achievable with this fiber composite material. Soundboard according to claim 1, characterized in that it contains a core plate and at least one outer fiber coating consisting of long fibers and carrier material. Soundboard according to claim 3, characterized in that the core plate has at least one recess within the area delimited by the outline of the soundboard, the total volume of all recesses being at most 80%, preferably between 20 and 45%, of the total volume of the core plate filled with material. Soundboard according to claim 3, characterized in that individual areas of the core plate have a different thickness. Soundboard according to claim 1, that the fiber coating is single-ply and at the same time multidirectional.

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