Online conference EuroBrake from May 17th to 19th 2022

It can be expected that many new and exciting development topics will be presented and discussed, which will be relevant in the production-related environment later. We wish all contributors success.

RTE is happy to support you in the implementation of practical measurement and testing tasks on brake components, in series production and in the development process. For series production, the focus is on robust testing solutions that bring reproducible results and ensure continuous monitoring of production quality.

On brake discs, the natural frequency measurement and the damping behavior are increasingly being taken into account by OEMs as quality criteria. The necessary measuring system for determining the damping behavior of the natural frequencies of brake discs has been offered and further developed by RTE for years.

In order to create a worldwide standard, a new ISO standard is currently being developed, in which RTE is also involved.

RTE AKUSTIK + PRÜFTECHNIK and Partner TMM at Control 2022!

The 34. Control will be held at the Stuttgart Exhibition Centre from 3rd to 6th May 2022.
You will find us together with our turkish partner TMM in Hall 6 – Booth 6111.

If you need a free entrance ticket, just send us a short email.

We are looking forward to your visit.

Read more.

Still up to date and on the agenda – the subjective acoustic test!

In many industrial sectors, subjective acoustic testing is still used today. It is always about 100% quality assurance. What is not taken into account is that the employee has to decide for several hours a day whether components are fault-free or not, regardless of their daily form and other influences.

In principle, humans have good qualities for recognizing difficult fault patterns. The more experience the employee has, the better the error detection. Influences on the employee, such as distraction, daily form, tiredness and lack of experience mean that errors are not discovered.

Internal and external complaints always lead to extra work, stress and, of course, additional costs. This can be avoided with the objective test.
Objective testing means that quality assurance is reproducible and reliable and the results are automatically documented. This meets the high requirements of customers and DIN standards.

The perfect thing is that with objective testing technology, the data is still available after the test and is available for continuous process evaluation and improvement. With the comprehensive SonicTC measuring and testing system, all data can be conveniently processed at any time, even at an office workstation, regardless of production activities.


The two testing technology specialists RTE Akustik + Prüftechnik GmbH and LAW NDT Mess- und Prüfsysteme GmbH decided to work together (January 2022). With this cooperation, two highly specialized companies in the field of non-destructive material testing are bundling their activities with the aim of being able to offer their customers new solutions in the future.

LAW NDT develops, designs and manufactures automated measuring and testing systems for 100% control in series production. In addition to its own eddy current crack detection devices, LAW NDT offers optical and tactile test methods as well as assembly and joining technology, including feeding and packaging solutions.

Supplemented by RTE’s field of competence, acoustic testing technology and the development of intelligent testing systems based on the SonicTC measuring and testing software developed in-house, comprehensive and, above all, new test concepts can be developed.

Contact us directly with your test task, we will be happy to support you.

A perfect team!
SonicTC testing software and IVS-500 laser vibrometer from Polytec

Acoustic testing with the laser vibrometer?

Yes, of course! The cause of a noise are vibration processes which are emitted as airborne sound via elastic bodies. Vibrations can be recorded using airborne sound or structure-borne sound as well as optically.

The IVS-500 laser vibrometer from Polytec, in combination with the SonicTC testing software, is a perfect expert system for noise and vibration testing. Especially when the acoustic test is subsequently integrated into a production process and expensive modifications are to be avoided. Existing ambient noise could have a negative impact on the measurement signal, or it would take a lot of effort to adapt the mechanics.

The IVS 500 is parameterized and controlled directly via the Ethernet interface with the SonicTC test software. Goodbye additional hardware or software ..

Ask us what is possible.

E-mobility: the challenge for quality assurance!

Testing of electric motors or entire electrical assemblies (e.g. air conditioning systems, car seats, sunroofs, pumps, adjusters, etc.) is one of our core competencies. Our SonicTC NVH (noise and vibration test) test system provides you with a powerful tool for analyzing, evaluating and testing devices and components. SonicTC ensures quality standards and sustainably reduces the costs of complaints and rejects.

The principle of the NVH check is comparatively simple. The implementation in series monitoring requires special experience and knowledge. During component testing, the noises and vibrations are characterized so that conclusions can be drawn about functionalities. In this way, on the one hand, the component is assessed in a quality-relevant manner; in addition, the statistical evaluation can then be used to determine and optimize the weak points of the component and the process.

Get in touch with us by phone or email. We are here for you.

SonicTC has completed its next evolutionary step and is now available as version 2.1. With SonicTC we have developed a modern and efficient NVH test software for noise, vibration and functional testing.

The demands on testing technology and its possible uses are growing steadily. Fast and convincing analyzes and results are expected. The software system should also be easy and flexible to parameterize, but still offer all the necessary evaluation functions.

Our SonicTC system is specially developed for quality assurance in series production. We place great demands on the versatile connectivity of the software for test bench control, from the Lin-Bus to the Can-Bus, everything is implemented in the new version for the automotive industry.

Today, users want to compare the test results from production with the data from the development department and its systems. It is also required to transfer the test features developed from laboratory test systems (Test Suites, Artemis, LabView, MatLab, etc.) directly to the production test bench. However, the different test systems are mostly incompatible and often use different methods and filters. With our SonicTC software the user gets exactly this adjustment functionality.

Ask us if you want to know more about it. Write an email to


Monitoring of quality characteristics in components and brake systems

The brake disc has a significant influence on the noise behavior of the brake system. Based on its material and construction-related properties, a brake disc shows some physical effects that must be taken into account for the reproducible monitoring of the resonance frequencies and their damping values.

In recent years, many automobile manufacturers have optimized the behavior of brake systems through material and design modifications. In addition to function and weight, the focus is also on the noise generated during braking. The aim is to minimize background noise in the vehicle interior. This topic reaches a new dimension in the field of electromobility, as electric vehicles have a significantly lower overall noise level than conventional vehicles.
Component-specific resonance frequencies are currently being monitored in the series production of brake components for quality monitoring when it comes to noise development. In addition to the resonance frequency itself, however, its damping behavior also plays a very important role in the development of noise. A high level of damping offers significantly less potential for noise development during braking.
In practice, the damping behavior is currently only examined in the development and prototype phase. Monitoring the damping behavior of critical resonance frequencies in series production enables significantly improved quality monitoring.

Detection of the resonance
Resonance frequencies are the fingerprint of a component. They do not change under comparable conditions and can be measured reproducibly.
To determine the resonance frequencies, acoustic resonance analysis is used, which uses the physical effect that a component that is excited to vibrate vibrates at its natural frequencies.
A brake disc exhibits many resonance frequencies that occur in certain component areas depending on the type of vibration, for example on the friction ring or on the pot. When it comes to the noise development during braking, it is mainly the modes of vibration on the friction ring that are relevant. They are used as a test feature for quality monitoring. These frequencies are usually in the range from 500 to 5000 Hertz.
The resonance frequencies and the associated waveforms have only been calculated theoretically in the development phase using the finite element method (FEM). However, the attenuation of a frequency can only be determined experimentally. For this reason, extensive laboratory measurements are carried out on the component itself in the prototype phase and then under dynamic conditions in the installed state.
Resonance frequencies are influenced by manufacturing and material tolerances. Due to the design and construction, there are areas in which some resonance frequencies are very close to each other or can overlap. In the case of series monitoring, it is therefore important to select test features that can be clearly detected and reliably evaluated, also taking into account the permissible tolerances.

Damping behavior
An acoustic signal contains all excited resonance frequencies of the component, each of which has an individual damping behavior. In order to be able to evaluate the frequencies individually, they are calculated from the time signal. The aim is to determine the value of the lowest damping for the relevant resonance frequencies.
This is more complex with brake disks than with other types of components. In particular, the waveforms on the friction ring of a brake disc show systematic changes in the area of ​​frequency and damping values. Depending on the measuring point, the measured values ​​for the same test feature can vary greatly.
In practice, systems have proven themselves that allow multiple automatic excitation at different measuring points on the circumference of the brake disc, also in order to minimize the effects of manual interventions. In combination with suitable mathematical algorithms, the value of the minimum damping for the relevant waveforms can be calculated from the recorded measured values. If necessary, a total value for the pane can also be output as a quality indicator.
In this way, the damping of a resonance frequency can also be determined and monitored as a feature in the series production of brake discs. Despite all the complexity, it must be ensured that the approach is practical and robust, and that the corresponding test systems are designed to be user-friendly.

Dagmar Metzger, RTE Akustik + Prüftechnik GmbH

Acoustic testing with a laser vibrometer on electric motors

Choosing the right sensors is essential for ensuring that the acoustic testing technology can be used as an objective testing technology in serial operation. In practice, all of the standard accelerometers (body-borne noise) and contactless sensors (air-borne sound microphones) that are available on the market are suitable here.

Measurements on difficult-to-access test components
A new feature of the SonicTC acoustic testing system is the integration of the control for the laser vibrometer by Polytec, based in Waldbronn. In recent years, the use of laser vibrometers as an additional option for contactless sensor technology for recording vibrations has established itself in test engineering. One of their intended uses is to take measurements on difficult-to-access test components and/or in test environments with high levels of background noise.
The laser vibrometer can, according to the company, be installed with the testing system quickly, simply and directly as a measurement sensor for the testing system. For example, the interface for a one-dimensional laser-scanning Doppler vibrometer IVS-500 is parameterised via a selection field, meaning that it is then immediately operational.

Scalable testing system for one or multiple test benches
The testing system is characterised by its scalability from one or multiple fully/semi-automated test benches. With the 2.1 release, the graphical, open programming supports the implementation of application-specific interfaces for single-user systems or fully automatic test benches in series production. The test stands can be operated simultaneously either in series or in parallel. The more complex the task is in terms of tests, measurement parameters and their correlation, the more apparent the strengths of SonicTC become.

The testing system is equipped with various communications solutions for higher-level systems, thereby ensuring the exchange of data in production lines and testing systems.
Thanks to its versatile analysis methods/evaluation methods/algorithms, the testing system can also be used in laboratories to evaluate measurement results. The procedures range from signal preparation to analysis of time and frequency ranges.

Acoustic material testing
Check workpieces non-destructively by means of acoustic resonance analysis.

State of the art

In order to avoid defective parts in mass production, innovative ways of process control, materials and quality assurance at low costs are required. A non-destructive test method (NDT) such as e.g. B. ultrasound, X-ray analysis, magnetic particle or eddy current testing is required and sometimes the maximum permissible defect size is specified. However, this information is hardly effective, because it is important that the workpiece meets the specified functional characteristics and does not fail in the field. The “classic” NDT processes combine objective sensory information with subjective human evaluation. The highest level of reliability cannot be achieved in this way.
The industrially applied acoustic resonance analysis (also called “sound test”) allows a fast, objective and 100% test of ceramic and metallic workpieces as well as composite materials.

Vibrations correspond to the properties of the work piece

Due to an external excitation, vibrations spread in the solid body: It vibrates in certain characteristic forms and frequencies, the so-called natural natural or resonance vibrations. They are, so to speak, the “language” of the test object. The vibration propagation in the material is characterized by elasticity, shape, material and structure and represents the mechanical properties of the body. Influences such as B. a crack, a different geometry or a change in material affect the resonance frequencies.
Acoustic material testing makes use of precisely these effects. By comparing the measured workpiece-specific characteristic values with stored reference values, quality characteristics such as “OK”, “cracked”, “material and structural defects” can be assigned from the resonances.

Resonance analysis is one of the volume-oriented NDT processes and evaluates defects in the material, while surface-oriented methods only assess these at or just below the surface. Classic methods have no relation to the mechanical properties of the component, while the resonance frequencies represent the mechanical strength.

Application steps

Test objects are subject to object-related, process-related or test-related influences. With the resonance method, only those properties can be assessed which influence the natural vibration behavior of the test object. If necessary, other influencing variables are to be eliminated mathematically. Taking the influencing factors into account, it is necessary to check whether the resonance analysis is suitable for the test task, i.e. H. the quality-relevant errors can be recognized. Proof of suitability is possible through a feasibility study, supported by a modal analysis (FEM). A few test objects are sufficient to assess whether resonance frequencies can be measured. Further measurements under process conditions record and evaluate possible influencing factors. The resonance analysis has been used successfully in industry for many years for fast and safe crack and structure testing of safety-relevant components.

Experience with users has shown, among other things:
• Temperature differences change resonance frequencies, but can be compensated for during the test become.
• In the case of sintered metal gears, exactly those parts failed after a torque load whose Resonance frequencies deviated from the good parts.
• Intelligent processes allow reliable sound testing of ceramic products and composite materials with high material and production-related scatter.
• The process brings the user considerable cost savings: Short test times, inexpensive automation, no consumables and documentation accompanying series production.

Forward-looking work and developments

The acoustic resonance analysis supplements the classic NDT methods for fast component testing. The aim is to make acoustic testing technology even easier and more effective for industrial use for the user. New processes such as pattern recognition and AI models will play an important role here.

2021, Jörg Ritter, RTE Akustik + Prüftechnik GmbH