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Acoustics for Engineers

2 hours course

Motivation | Contents | Goals | Aspects | Manuscript | Concept

Practise

 

Motivation

Asking anyone about the most annoying environmental Umweltbelastung the answer will mostly be

                                                    Noise

This should be a reason for the mechanical engineer to get familiar at least with basics of acoustics, since noise sources would be very often an otherwise useful machine.

Basically, noise is a vibration problem, but in addition to classical vibration theory is is not only a question of physics - measuring and evaluation will be necessary according to physiological viewpoint.

For the mechanical engineer, knowledge of basic acoustics will be interesting even within the design phase in respect to noise reduced design.

Noise reduced design means

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Noise should be minimized at its source

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Noise should be antagonized early

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Noise should be avoided reasonable

Contents

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Viewpoints, rating ad targets of acoustics

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Vibration theory from measuring point

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Frequency analysis an mechanical impedance

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Physical foundation of acoustics

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Airborne noise

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Structure born noise

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Noise sources in machines

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Noise reduced design

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Secondary noise reduction

Goals

What means acoustics compared with usual vibration theory?

From engineering standpoint, acoustic is basically only a special topic of vibrations. Therefore, in acoustics many already well known themes will be found again. What is the special thing of an acoustic lecture?

New will be the strong aspect of measuring. Acoustic is always connected with human impact. Therefore, acoustics will always require sophisticated measuring techniques. Measurement will now be a fundamental topic.

New is a strong part of frequency analysis, since the human ear itself is the most powerful frequency analyzer. What is the meaning of Fourier? His theories - complicated an abstract? Indeed, they are not!

New is the investigation of mechanical vibrations in a higher frequency range. Therefore, some classical methods will not work anymore and have to be expanded.

Aspects

In mechanical engineering, acoustics today is important as well as unpopular. Important because of the high annoyance of noise. Unpopular because of expenses of acoustic measures which makes acoustics very oft be judged as being unproductive (however, a shortsighted viewpoint). However, it might be interesting and profitable for an engineer to specialize on acoustics. It's a goal of the course to give the student the sensitiveness to handle these controversial problems.

Manuscript

A manuscript is available (in German language). Additionally, the students will get an elaborated catalogue of questions which should be answered over the course. This will result in a consolidation of the stuff, siche the questions contain a number of difficulties found in practice. After the test, the students will get additionally a script with the carefully elaborated answers as supplement of the manu.

The elaborated questions are part of the test at the end of the course.

The Concept

There is only space of two hours a week for a subject that could cover a complete discipline. How to fulfill?

It would be possible to start schoolmasterly with excessive basics and continue up to the end of the semester. but this will not lead beyond basics.

It would be possible to tell a lot of practical stories. Interesting maybe. But in practice there will arise more questions, other problems.

Let's try it otherwise!

Defining a clear target - noise reduced designing. That means to handicap noise at its origin.

Mathematical basics cannot be avoided. Again starting with ┤... what is a vibration?┤

Indeed, it will begin in that way. But now we take a new viewpoint:

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From the viewpoint of measurement - it's always one of the uppermost topics in acoustics
 

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Evaluation not only from mechanical but furthermore from physiological viewpoint - background is always annoyance
 

If we not get caught in banalities, we will proceed well. Again we meet names like Fourier or D┤Alembert

No - not again derive Fourier integrals, convergence proving, calculate series coefficients. It is much more interesting to look at the primary set on. To think about what Fourier basically says to us (he was natural scientist and not a mathematical theorist). And the result is astoundingly uncomplex.

Numerical methods in acoustics - this topic would got beyond the scope of the course. However, knowing the mathematical and physical basis will enable to understand these method and judge then for their usefulness.

A carefully elaborated manuscript together with the catalog of question will help to cover this large stuff within such a short time.