articol despre bassoforte.pdf

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Sound Characterization of a New Experimental

Bassoon: the Bassoforte

Timo Grothe

Erich Thienhaus Institut, Hochschule fr Musik DetmoldDetmold, Germany

Based on an idea of Guntram Wolf, an interdisciplinary

team of musical instrument makers, engineers,

and musicians developed a new bassoon. Te first

fully playable prototype of the new instrumentcalled the

Bassofortehas been tested at the Hochschule fr Musik

Detmold, where the present author carried out a series of

acoustical measurements to characterize the Bassoforte in

comparison to the modern German bassoon.

In 2009, Guntram Wolf came up with the idea to develop

a wind band bassoon. Adopting design principles Wolf along

with Benedikt Eppelsheim of Munich had already success-

fully brought into practice with the Contraforte and more

recently the Lupophon, this series of modern double-reed

instruments should now be completed with the Bassoforte.

Te development of this new bassoon-like instrument was

accompanied by an interdisciplinary research initiative at the

echnische Universtitt Dresden, where the present author

had at that time worked on double-reed research during

his PhD under the supervision of Prof. Roger Grundmann.

Te practical development process of the new instru-

ment as well as some of the modern German bassoons

peculiar acoustical properties (including air column and

tone hole concept) that have inspired the Bassofortes design

have already been reported in German inRohrblattand in

English inDouble Reed News(British Double Reed Society).1Tis article presents a comparison of the sounds of the

bassoon and the Bassoforte using the first fully playable

prototype of the new instrument.

Specications of the Bassoforte

So that the reader may better understand and interpret the

measurement results, a short overview of the Bassoforte

will be given here, along with some of the objectives that

led to its invention.At the heart of the development of the Bassoforte was

Guntram Wolfs wish to make an instrument for bassoonists

to play in a wind band. o compete with the brass instru-

ments, it should play louder and have a clearer sound color

than the modern bassoon. Te new instrument should

Figure 1a. TheBassoforte (r) next

to a modern Germanbassoon.


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98 SOUND CHARACTERIZATION OF A NEW EXPERIMENTAL BASSOON: THE BASSOFORTE

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provide an even and stable tuning through a logical

fingering system. (After all, the instrument should still

be intuitive for bassoonists to play.) And, the instru-

ment should preserve the typical double reed sound.

As it became obvious that achieving a greater dynamic

range and clearer sound required a drastic redesign ofthe bore and tone-hole concept, a larger objective arose:

to design a new air column that overcomes some of the

intonation troubles inherent in the modern Heckel/

Almenrder concept.

After many tone hole calculations and recalculations,

laboratory measurements on simple mock-ups, and

development of manufacturing strategies and special

tooling, the initial ideas came to fruition in this first

version of the Bassoforte.

Widening the conical bore created a greater dynamic

range and tonal volume (the Bassoforte has a taper of

1/56 compared to the 1/70 typical for bassoons). Te bore

was elongated, extending the bass range by a semitone to

A1. Manufactured of maple, this first version Bassoforte

is considerably heavier than the bassoon and so comes

with a spike to rest on the floor for convenient playing.

Te tone holes are short and wide and fully operated by keys. Tis helped in making a

more ergonomically convenient keywork. As shown in Figure 2, the positions of the fingers

are identical to what would be used on the bassoon. However, the Bassoforte has four addi-

tional keys (marked by bold characters in the following picture):

Ef : No fork fingering is needed for E f3. Te Efkey operates an Efhole.

A: Te Bf1 hole is closed by the little finger of the left hand, to play the lowest

A1 (all holes closed).

o (octave key): Contrary to the bassoon, the Bassofortes piano hole (whisper key)

is closed by default. o overblow the octave, press this octave key to open the

piano hole. Te additional action of the right hand for notes higher than C4 is

obsolete (Cs4F4 are fingered like Cs3F3 with additionally pressed octave

key). f (flageolet key): Tis key opens the flageolet hole on the bocal, some centimeters

downstream of the reed which facilitates overblowing to the twelfth (Fs4-C5 is

fingered like B3-F4, using the flageolet key instead of the octave key).

Te Bassofortes fingering system is different but logical, requiring less finger action in the

right hand for the overblown notes. It overcomes the need for the many odd helper fingerings

that are needed on a German bassoon to establish proper intonation.2

Figure 1b. Reeds for bassoon (l)and Bassoforte (r).

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Scientic Study

Te completion of the fully playable prototype enabled the following comparative in vivostudy.

Acoustical Measurements

Four different measurement methods were applied to both the bassoon and the Bassoforte:

1) Measurement of acoustic input impedance to determine the air column resonances

2) Calibrated sound pressure measurements of single notes in a reverberant chamber

to determine the upper dynamical limit3) Measurements with an acoustic camera in a concert hall.

4) Studio recordings of music to investigate sound color by means of spectral

characteristics.

Figure 2. The Keywork of the Bassoforte. The four extra keys are marked

with bold characters (Ef , A, o, f).


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1) Air column resonances

Although the player influences the sound to a large extent by his reed design, embouchure,

and blowing technique, the intonation properties and the generic sound color of reed wind

instruments are determined by their air column.

Acoustic impedance is the ratio of pressure to acoustic volume flow. It is a local quantity

that, in a pressure antinode of a standing wave, has a maximum because the acoustic volume

flow in the denominator becomes very small. When measuring the acoustic impedance at

the input end of wind instrument resonators, observed peaks in the impedance spectrum

indicate air column resonance frequencies. Near these peak frequencies, vibrations of theair column are initiated easily because only a very small volume flow amplitude is needed

to establish the pressure standing wave.

Te input impedance spectrum is the acoustical fingerprint of the resonator. It is a very

convenient and reliable measure as it can be measured without reed and musician.

Figure 3 shows the acoustic impedance spectra of some corresponding fingerings on

bassoon and Bassoforte. (o produce these plots, the measured impedance curves have been

corrected for reed mouthpiece equivalent volumes; 1.8 cm3for the bassoon and 3.4 cm3for

the Bassoforte.) Te vertical black lines mark the fundamental frequency and its integer

multiples of the note corresponding to this fingering. It is observed that the first peak of the

Bassoforte accurately matches the fundamental frequency.Furthermore, due to the greater regularity in its tone-hole grid, the Bassofortes higher

impedance peaks align slightly better to integer multiples of the fundamental. Tis is an

indication of greater tuning stability.

Figure 3. Acoustic impedance curves of four notesB f1 (f0= 59 Hz), B f2 (f0= 117 Hz), F3 (f0=175

Hz), and B f3 (f0= 235 Hz)for bassoon and Bassoforte. The curves are shied vertically forbetter readability of the plot. Vertical black lines mark the partials of the sounded note.

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As mentioned above, the impedance curve excludes the effect of the musician, and so

the interpretation of these curves is somewhat vague. However, a general and meaningful

difference is clearly observed: the cut-off frequency, which is the threshold above which

sound waves propagate in the air column, is shif ted. Te cut-off is indicated in the impedance

curves by the occurrence of smaller, irregular peaks. For the bassoon curves shown in Figure

3, the cut-off is found around 500 Hz whereas at the same point the Bassofortes impedancepeaks are still well aligned. Tis aspect will be further discussed later on.

2) Reverberation chamber measurements

o measure the dynamics and sound of the instrument, it is necessary to consider not just

the resonator but the full systemto measure the sound pressure created by the reed

and player in their surrounding acoustic. Tis then brings up the question of the optimal

microphone position for comparable recording of both instruments.

Generally, the bassoon has a complex radiation pattern, due to the distribution of tone

holes across the long and slim instrument body. Te Bassofortes radiation pattern may be

different, since the tone holes are shifted and pads are hanging above all of them. o create

a measurement configuration insensitive to differences in radiation characteristics, we

decided to measure both instruments while they were played in a reverberation chamber.

In such a roomwith oblique, sound-reflecting wallsa diffuse sound field develops. Tis

means that the air particles are moving randomly without dedicated directions. Terefore,

given a stationary sound excitation, at every position in this room the sound pressure will

be the same. Furthermore, the sound power wil l be proportional to the square of the sound

pressure.

As we were interested in comparing the sounds of the bassoon and Bassoforte in terms

of their overtone content and measuring the upper dynamic limits of both instruments, the

reverberation chamber at the Erich-Tienhaus Institut of Hochschule fr Musik Detmold

provided an ideal measurement environment. Te measurement system was not very convenient

for the player, however, as he was advised to play as loud as he could on both instruments.

Averaging many repetitions of the same note, played and recorded at several positions in the

room with calibrated measurement microphones, we found that the integral sound power

radiated from both instruments is about the same (see Sound pressure level in able 1).

But as the sound of the Bassoforte has much more energy in the higher overtones, it

appears to be significantly louder to our ears. Tis is reflected in the results for the loudness

(see Loudness in able 1). Loudness is a psychoacoustic measure that takes the frequencydependent sensitivity of the ear into account when quantifying perceived dynamic level. It

is measured on the Sone scale, with a doubling in Sones expressing a doubling in loudness

perceived. (Tis relationship is different in the logarithmic Decibel scale used for A-weighted

sound pressure levels).

Bf1 Bf2 F3 Bf3

Sound pressurelevel [in dB(A)]

bassoon 88.9 93.7 95.1 96.1

Bassoforte 92.6 92.6 95.2 97.7

Loudness(in Sone)

bassoon 68.7 78.2 87.3 92.3

Bassoforte 75.7 82.0 97.7 106.1

Table 1. Sound pressure level and loudness of bassoon and Bassoforte notes played in a rever-beration chamber


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Te sound spectra measured in the reverberation room are shown in Figure 4, where

we can observe that the spectral envelope over the peaks (which characterize the strength

of the overtones) is about the same in the frequencies up to 1 kHz. However, the overtones

in the Bassoforte between 2 and 4 kHz are significantly enhanced as compared to those of

the bassoon.

3) Acoustic camera measurements

For musicians, a much more common surrounding than the reverberation chamber is a

concert hall.We asked our musician to repeat the experiment in the large concert hall at the Hochschule

fr Musik Detmold. o measure and visualize the sound radiated from the bassoon, we used

an acoustic camera.

An acoustic camera is a two-dimensional array of microphones (we used the system

Noise Inspector by CAE, Gtersloh, Germany, with forty digital MEMS microphones). Te

differences in time of flight and in the pressures at the nodes of this array allow for an esti-

mation of the locus of the sound source. Te distribution of sound power in a plane parallel

to the array, typically at the same distance as the sound source, can then be calculated. In

the center of the array is a camera, and to its optical image the acoustical image from the

microphone analysis can be overlaid in real time. Tis allows an intuitive and demonstrativeinspection of the sound field (see the snapshot shown in Figure 5). Te frequency range of

the microphone analysis was here adjusted to between 2 and 4 kHz. Tese visualized sound

measurements confirmed the large dynamical difference between bassoon and Bassoforte

in this frequency band as observed in the previous experiment. Despite the differences

between bassoon and Bassoforte in terms of tone-hole design, their locations relative to the

Figure 4. Sound spectra of four notesB f1 (f0= 59 Hz), B f2 (f0= 117 Hz), F3 (f0=175 Hz), and B f3

(f0= 235 Hz)played on bassoon and Bassoforte. The curves are shied vertically for betterreadability of the plot.

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main bore axis, and in their coverage by keywork, we were not able to identify a significant

difference in radiation characteristics.

4) Studio recordings

o compare the sound color of both instruments in more detail, we asked another musician to

play both instruments in a recording studio. Five studio microphones were set up at various

distances from the players position by a professional sound engineer in the recording studio

of Hochschule fr Musik Dresden. o get comparable sound files, the musician was sitting

and trying to keep both instruments in the same position relative to the microphones. In

contrast to the previous single note measurements, we now asked the musician to play ashort piece of his choice.

In the subsequent analysis, we cut short snippets of constant pitch and analyzed the

sound spectrum separately for each of the five recording channels. Te process of inspection

of the spectral envelope of the overtones mentioned earlier allows the creation of a timbre

characterization from a formant analysis.

A formant is an elevation in the spectral envelope that occurs when a group of neigh-

boring overtones are pronounced in the spectrum. Te center of gravity of this raised

frequency band is the formant frequency. Formants are the reason we can identify vowels

independently of pitch. Te existence of one or more formants in a sound and the ratio of

their center frequencies strongly influences timbre perception. A rough characterization ofa complex musical sound can be made by comparing it to the formant frequencies of vowels.

Te formant analysis of our bassoon and Bassoforte sounds revealed three formants below

3 kHz. Tese occur near 500 Hz, 1 kHz, and 2.1 kHz, as shown in Figure 6 (following page).

Te shaded regions mark the spread of formant frequencies as observed from the five dif-

ferent microphone positions. Here we can observe two characteristic differences: 1) Te

Figure 5. Snapshot of acoustic camera recordings of the note D2 (f0 = 73.9 Hz) played onbassoon (right) and Bassoforte (le) in the concert hall of Hochschule fr Musik Detmold. The

distance between camera and musician is 2.7m, the analyzed frequency band is 2-4 kHz. Thecolors display sound pressure levels according to the color bar below the image (in dB SPL).


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Bassofortes third formant (around 2 kHz) is higher compared to that of the bassoon. 2) Even

more significantly, the curve of the Bassofortes main formant increasingly shifts from 500

Hz to 750 Hz as it approaches the upper end of the low register. At the register margin, the

formant drops rapidly back to 500 Hz for overblown notes above F3. Te main formant of

the bassoon, on the other hand, barely changes for these same notes.

Whereas the energy boost between 2 and 4 kHz and the increased third formant are

individual sound characteristics that give the Bassoforte a recognizably enforced sound

when playing along with the brass instruments of a wind band, the shifting of the main

formant is an indication of an unevenness in timbre. Our ears spectral analysis identifiesthis shift easily: Te tone color becomes very open and nasal for the notes D3 to F3. Tis is

definitely an aspect to reconsider when creating a second, refined version of the Bassoforte.

Coming back to the input impedance measurements of the resonator (Figure 3), we

find an interesting relation between the cut-off frequency of the air column and the main

formant center frequency. Te importance of the cutoff frequencys impact on timbre has

already been emphasized by Arthur Benade4but was not studied in a systematic way. Te

present results are an indication that the wind instruments rear end (the open tone holes

in the downstream part of the bore after the first open, pitch-determining hole) creates

formants. Tis hypothesis provides a link between the geometric design of the resonator

and its sound color attributes; a link that can help further developments and may be of usefor a directed sound design.

Figure 6. Formant center frequencies in the sounds of bassoon and Bassoforte. The shaded

regions mark the scattering of observed center frequencies from the ve dierent microphonepositions. The dashed horizontal lines mark the center frequencies of the vowels o, , a, and e.3

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Conclusion

Standard acoustic measurements provide an insight into the acoustical properties of the

Bassoforte. As compared to the modern German bassoon, it can be shown that the Bassoforte

plays significantly louder and has more overtoneswhich may increase the audibility of

bassoon parts in wind bands. Furthermore, an unevenness in timbre is shown by meansof formant analysis. Te results indicate that the acoustical properties of the air column,

namely the cut-off frequency, should be taken into account in further developments of the

Bassofortes tone hole design in an effort to correct unwanted nasality.

odays orchestral instruments have undergone centuries of development and the

remaining modifications with which instrument makers experiment nowadays are small (if

they experiment at all) and the yielded effects are matters of nuancecertainly important

to musicians, but oftentimes complicated to measure and to understand.

In this context, however, it was a fascinating opportunity for a researcher to study an

instrument such as the Bassoforte, which is a quite drastic redesign when compared to

other state-of-the-art descendants of its family. It is also a testimonial to the spirit of the

company of Guntram and Peter Wolf, which dares to undertake experiments like these: In

order to better understand the performance characteristics and experience the sound of a

new instrument in a musical context, it was crucial to stop doing laboratory measurements

on modified mockups and to instead build a fully playable prototype to be evaluated in vivo

by musicians.

It will certainly require more time to further develop the Bassoforte, but already it has

provided much invaluable experience to the multidisciplinary team who has dared to leave

the beaten path.

Timo Grotheis a trained woodworker fascinated by musical instrument

making. He experimented in self-taught string instrument making (guitar

and cembalo) and later studied mechanical engineering at echnische

Universitt Dresden. As a graduate student, he had the opportunity to

join the research team of Prof. Roger Grundmann, who just had developed

a new bend for the bassoon bocal based on computational fluid dynamics.

For his very recently submitted PhD entitled Experimental Investigations

on Bassoon Acoustics, Grothe developed an artificial mouth for double

reeds, an experimental setup that allows researchers to precisely measure embouchure actionsunder realistic playing conditions. Grothe is now at Hochschule fr Musik Detmold, where he

teaches and researches musical acoustics at the Erich Tienhaus Institut (EI) for onmeister.

Acknowledgement

Professor Malte Kob is acknowledged for his support in the measurements carried out at

Hochschule fr Musik Detmold. Tanks to the bassoonists Stefan Pantzier(studio record-

ings) and Hannes Fritsch(reverberation chamber and concert hall). Maximilian Pauls of

Hochschule fr Musik Dresden carried out the studio recordings. Help with the acousticcamera was provided by Nico Zurmhlen of CAE.

Te Bassoforte is the result of a research agreement between Guntram Wolf Holzblasinstrumente

GmbH, Kronach, and echnische Universitt Dresden. Benedikt Eppelsheim largely


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contributed to the Bassofortes acoustical design, and throughout the development Stefan

Pantzier provided valuable advice from the viewpoint of the musician and reed maker.

Te contribution of the present author in the development of the Bassoforte was supported

by the German Federal Ministry of Economics (BMWi) in the project ZIM-KF2229603.

Professor Roger Grundmann and Dr. Johannes Baumgart are also gratefully acknowledged

for their scientific support.

Endnotes

1 imo Grothe, Das Bassoforte: ein Fagott fr die Harmonie,Rohrblatt27 (2012): 83-87.

imo Grothe, Te BassoforteA Bassoon for Wind Bands, trans. Michael Johnson,

Double Reed News: Te Magazine of the British Double Reed Society, (Summer 2013):

8-12.

2 James Kopp, Te Not-Quite-Harmonic Overblowing of the Bassoon, Te Double Reed

Vol.29 No.2 (2006): 61-75.

3 Jrgen Meyer,Acoustics and the Performance of Music: Manual for Acousticians, Audio

Engineers, Musicians, Architects and Musical Instruments Makers(Springer, 2009).

4 Arthur Benade,Fundamentals of Musical Acoustics(New York: Dover Publications, Inc.,

1990).

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