PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

The consolidation of Engineering Acoustics as an example ofcontextual history of science
Joachim SCHEUREN
Müller-BBM GmbH, Germany

ABSTRACT
Following widespread practice in natural sciences, the history of Acoustics is mostly understood and depicted as a sequence of scientific ideas and achievements provided by ingenious individual scientists orscientific schools. Even if this approach is accepted because it foregrounds the sequence and relation of ideas,
it risks to ignore the driving energy of any social and technical context. This is particularly true for appliedsciences like acoustics which, from a certain level of scientific insight, are much more driven by the needs oftechnology than by purely scientific interest and curiosity.
The mutual influence and dependence of scientific, technological and social determinants can be illustrated
exemplarily for the renaissance of acoustics in the mid of the last century. Being underestimated as conclusively understood and lacking new challenges, the relevance of Acoustics changed significantly with thedemands of the post-war era. The respective requirements were able to initiate an iterative process linking
technological progress and needs with new scientific insight. With reference to some typical examples it will
be shown how these interactive efforts finally established the disciplines of engineering acoustics and noise
control which essentially contributed to renew and strengthen acoustics as an indispensable interdisciplinary
field.
Keywords: History, Engineering Acoustics

1. INTRODUCTION
Being - from a superficial point of view - a chronology of relevant scientific events and findings
only, any deeper interest and insight in - as well as benefit from - history crucially depends on understanding the context, i.e. the mutual dependencies, influences and impacts which drive or co-drive
at least all historic developments and relationships. This equally holds for the history of science where
the temptation to undervalue scientific and social contexts is increased by the fascination of many
outstanding singular scientific findings of excellent individuals.
However, the real benefit of historical considerations can be found if all “who”s, “when”s and“how”s are complemented by understanding the “why”s. This may particularly apply to physicaldisciplines of high technological impact. A well-known example is given by the extremely rapid
progress of nuclear physics forced by political urgency and priority in the last years of world war II.
Although being a most questionable example of forced, even misguided technical progress, it can bestated that extreme promotion and support only enabled great physical and technological progress inan unimaginably short time.
Comparable conditions of highest needs were found in the reconstructive era after world war II
where the many wartime devastations had to be overcome as fast as possible. The urgency of basic
reconstructions together with increasing demands later provided an environment of exceptional fertility for developing, understanding and applying sound control, its preconditions and its implications.
Thus, the then occurring revival of Acoustics was characterized by the growing need to apply
physical insight to actively influence and control our environment, the world around us. Although it
belongs to the basic branches of physics, there was, in the 19th century even, no imagination yet
about the immense technological all-day relevance acoustics might have in some future. On the contrary, mechanization had to become very advanced to make aware that all its requirements needed asystematic involvement of acoustic aspects. Thus, starting from “Technical Acoustics” as definedand developed in the first half of the 20th century, engineers more and more developed, applied andfinally consolidated the acoustics they needed: “Engineering Acoustics”.
It is obvious from this mutual interaction that the relevance of technical and engineering acoustics

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caused a revival of acoustics as a whole by initiating many new research and development activities
and thus - in an iterative procedure - by contributing to and benefiting from progress in the wide fieldof acoustics. So, the stimulus which continuously turned acoustic demands to modern technology, haspromoted acoustics to become an important part of applied science again which - by its most interdisciplinary character – is crucially linked up with nearly all technological disciplines and thus became ahighly needed, essential part of today’s technology and science.
It is interesting and instructive to have a closer, historical look to inventiveness and scientific/technological successes of this period. They all appear as results of pioneering works and ideas ofindividual scientists. In spite of the short temporal distance since then, a historical classification ofoutstanding lifetime achievements of the most relevant German “schools” of this time can be found involumes 10 and 11 of a series of publications recently edited by the German Acoustical Society, DEGA([1]). However, these enlightening booklets do not aim to identify and follow the close links between
physical, technical, social, political and individual needs and deliverables which enabled and promoted scientific progress of acoustics in the interdisciplinary field of engineering and technology bymutual interaction.
It is this context, the simultaneousness and mutual incentive of (human) needs, (physical/scientific)
insight and (technical) realisability, which launched a fruitful renaissance of acoustics in tow behindengineering acoustics. And it is this context which this paper tries to deal with by illustrating themutual dependence and driving energy of needs, scientific findings and practical solutions. If consequently followed up and concluded, this approach should have the potential to complement and consolidate the review of individual scientific achievements, as compiled and acknowledged in [1], byrevealing the environment which - at the same time - required and enabled them. And this is what weunderstand and aim as contextual history.
Accepting some abstracting simplification, the mutual interaction of growing demands (requirements), progressive insight (science) and innovative technology (realisation) can be depicted schematically within an iterative cycle of research and development. As long as practical engineering tasks andsolutions are involved, such interaction between research and development is not driven for its own
sake. Instead it typically follows practical needs and technical possibilities. Therefore, any practiceoriented cycle of research and development involves
x technical implementation and realization of new research results and approaches,
x practical application of technical realisations to meet given demands andx increasing demands stimulating new research again.
It is interesting and fascinating to identify and to illustrate the mechanism of interdependence andmutual influence between research and development as driven by and for practical, i.e. applied soundcontrol engineering.

Figure 1 – Iterative cycle of research and development involving implementation and application
Fig. 1 schematically illustrates this cyclic procedure which also defines the interactive role of engineering acoustics ([2]). Following this flowchart shows how - starting from direct contributions toresearch - engineering acoustics can help tox develop concepts and solutions, then tox technically implement these to solve practical acoustic problems, tox apply the technical solutions to reality and finally - by assessing its success - tox formulate the need for improvements or new approaches which should be a matter of research again and thus finishes the closed cycle loop.
It was this ongoing procedure which maintained progress and success of engineering acoustics
from the mid of the 20 th century to these days and which thus initiated the recapture of acoustics froma basic and well-established discipline of physics to a highly topical discipline of modern technology.

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2. TECHNICAL ACOUSTICS BEFORE 1950
Although the term “Acoustics” first appeared in 1693, the science of sound may be traced back to
the cradle of our culture (e.g. Pythagoras). Starting from relating qualitative hearing events to quantitative numerical ratios by Pythagoras, the cultures of our world were able to continuously develop
and provide a deep understanding of our hearing and its physical causalities and relationships. Consequently, the scientific understanding of acoustics could be summarized in advanced, comprehensive
theories of sound in the 19th century already. Hermann von Helmholtz’ “On the Sensations of Tone”(1862) as well as Lord Rayleigh’s “Theory of Sound” (1894/96) are the most prominent and lasting
examples.
In parallel to the scientific exploration of Acoustics the end of the 19th century saw a rapid development of electroacoustic technologies to transduce, register, transmit and reproduce sound. Thus established “Technical Acoustics” was the starting point for growing relevance and involvement of acoustic
issues within the process of industrialization in the 20th century ([3]). At first this development focusedon providing and supporting desired sounds (sound transmission, -reproduction and -distribution). In
addition to developing and extending worldwide broadcasting of sound signals via phone and radio
networks as well as tape and disc recordings, W.C. Sabine was able to lay the foundation for targeted
design and layout of auditory rooms to best adapt them to speech and music.
However, technical reduction of undesired sounds was increasingly recognized as an important discipline, indispensable even for progressive mechanization of our world. Significantly interested
circles thus were sure in the early 20 th century already that noise abatement was a public duty, being
claimed for instance by the first German noise abatement society founded in 1908.
Acoustics and Technical Acoustics tried to meet the respective requirements by successful research
activities as well as by new findings and development results. Apart from complementing and completing the far-sighted frameworks of Helmholtz and Rayleigh, this led to increasingly systematicinvestigations of sound generating, sound transmitting and sound controlling mechanisms. Exemplary
examples werex Berger’s mass law (1910)
x Derivation and validation of practical approximation formulas
x Introduction of “dB” (1920s)
x Introduction of loudness characterization in “phon” (1926)
x Derivation and experimental verification of coincidence effect by Cremer and Eisenberg(1942/48)
x Development and provision of versatile measurement technology
x Development and provision of theoretically and empirically well-founded state-of-the-art forthe most important disciplines of Technical Acoustics.
In total, in the middle of the last century Technical Acoustics may be described as a discipline whichfeels committed to the fascination of new technical possibilities (electro acoustics) and quality-conscious hearing requirements (room acoustics) but also to a still weak social awareness of
detrimental noise effects (noise control). By orienting successive insight along the requirements ofincreasing mechanization, Acoustics had been able to recommend itself as an important instrument ofprudent engineering activities: Technical Acoustics thus had become Engineering Acoustics.

3. ENGINEERING ACOUSTICS AFTER 1950
Reconstruction in Europe after devastating world war II had to fulfil so many basic needs thatminor relevance only could be given to all questions of sound comfort. But it just was the mechanization which - being consciously experienced during new reconstruction - resulted in increased
prosperity and thus implicated higher quality demands. Slowly but steady, in the following years thesedemands then found their way into planning and approval procedures. The consideration of quality
demands became more and more important when new efficient and material-saving construction andproduction methods at the same time had to fulfil higher durability and stability and improved acoustical/vibrational characteristics. Engineering Acoustics thus was given a growing, indispensable
cross-sectional function within almost all engineering disciplines. Without timely involving Engineering Acoustics, it became more and more difficult to realize optimal operating conditions, environmental compatibility of technical systems, plants and processes or even growing demands for better
functionality and comfort of technical products.
In Germany, the nucleus for managing and upgrading this acoustic engineering work was found in7004

some prominent scientific centers which were founded or further developed after the war in Berlin,
Dresden and Göttingen. Soon, acoustic engineering offices evolved from these centers which could
provide acoustic know-how and experience as well as acoustic specialist knowledge to companies andauthorities which thus were able to cope with new acoustic issues and problems. Iterative interactionof these scientific centers with the practice oriented work of acoustic engineers continuously enhanced
state-of-the-art knowledge and thus set the basis for development of a new interdisciplinary discipline.
Although a growing number of private and public institutions today have own acoustic competence,
specialized acoustic engineering companies still are of central relevance. Apart from their specificpotential of knowledge and experience, this relevance is based on exchange of acoustic insight andmethods between different application fields. While the work of specialized departments often isconstrained by their limited applicative area, diversified acoustic engineering companies benefit fromexperiences and methods which initially were tailored to different applications.

4. FOCUS OF ENGINEERING ACOUSTICS TODAY
Today, engineering acoustics is a widely acknowledged cross-sectional discipline which necessarily has to be involved systematically to meet ambitious requirements to environmental compatibility of systems, plants and products. Although recent requirements may particularly focus on traffic
and transportation noise, other areas like effective limitation of industrial and neighborhood noise ornoise at working places need competent involvement of Engineering Acoustics in planning, design,
approval and layout. In addition to this, engineering acoustics today equally play a significant role inactively designing various sounds, particularly if rooms are to be acoustically optimized for specificuse or if specific product sounds are to be realized.
Engineering acoustics has been able to cope with this profile of requirements by growing standardization and automatization of its planning and developing activity and today has got modern tools
which essentially facilitate analysis and assessment, prediction and targeted control of sounds. Illustrative examples of successfully involving and applying engineering acoustics arex modern computer-aided technology and methods to register and evaluate acoustic signals,
x integration of subjective parameters and assessments into the characterization and assessment of sounds and their effects,
x progress in problem-oriented modelling of acoustic fields and mechanisms for application
specific simulations and predictions,x continuous development of simulative calculations and assessment criteria in room acoustics,
x targeted definition and realization of product sounds particularly for automotive sounds,
x essential progress in technical analysis and reduction of road-, rail, and aircraft noise,x high environmental compatibility of industrial plants by technical means,x successful research, provision and implementation of innovative methods for active controlof sounds and noise.
These examples illustrate how engineering acoustics has successfully established itself as an indispensable part of modern engineering and technology. This in turn has revitalized the classic field of
acoustics which, at the time, tended to be underestimated as conclusively understood and lacking newchallenges. The roots of this turnaround were clearly set in the diverse environment of after war
reorientation. Therefore, this is an impressive example of the effectivity of many mutually reinforcing
influential factors on partial disciplines of science and technology, an example of the importance ofcontext and its mutual dependencies.

5. CONCLUSION AND OUTLOOKIn spite of all progress in the last years and decades: the physically complicated wave nature ofsound and vibration fields remains a challenge to continuously improving state-of-the-art engineering
acoustics by innovative research and development. This is because only powerful engineering acoustics are able to ensure high standards and environmental compatibility for growing mechanization andmobilization of our world.
Although being the result of numerous individual efforts and successes, the overall development ofengineering acoustics was strongly determined by the specific melting pot of the postwar period. This
impressive example of contextual energies would deserve a complete, well balanced investigation andrepresentation of the underlying historical relationships.

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REFERENCES
1. Költzsch, P. Schriftenreihe zur Geschichte der Akustik. Vol 1 - 11,
published by DEGA, Deutsche Gesellschaft für Akustik, Berlin, www.dega-akustik.de
2. Scheuren, J. Entwicklung, Bedeutung und Perspektiven der Ingenieurakustik zwischen physikalischer
Wissenschaft und angewandter Technologie. Fortschritte der Akustik, DAGA 2016, Aachen, p.1-14,
Deutsche Gesellschaft für Akustik, Berlin, 2016.
3. Beyer, R.T. Sounds of our times. Springer, Berlin, 1999
4. Scheuren, J. 100 Jahre Technische Lärmminderung in Deutschland.
Zeitschrift für Lärmbekämpfung 49(6), 2002, S.199–218.

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