Acoustics and control: NVH development, sound design, and intelligent vibration reduction

Airborne noise is an important factor not only in product development and quality assessment but also in private settings. Certain sounds are intentionally present and meant to create a positive impression, while others are unwanted and disturbing and need to be identified and, if necessary, modified or eliminated. Additionally, there are numerous regulations regarding maximum permissible sound pressure or sound power levels that must be observed.

We offer measurement and solution approaches for all these airborne noise challenges. To comply with specific limits, we can perform sound pressure level measurements or determine sound power according to standards.

To evaluate the sound impression of products or noises, we conduct objective measurements and determine relevant psychoacoustic parameters. Additionally, subjective evaluation through participant surveys can be carried out. The results then serve as a basis for optimizing the sound impression, up to sound design.

To improve acoustics in enclosed spaces, we can determine the acoustic properties of the materials you use, such as absorption coefficients or transmission loss, through standardized measurements.

For enhancing room acoustics, we perform reverberation time measurements on-site. Based on these measurements, we develop a tailored target concept with measures to optimize the room acoustics according to your requirements.

Vibrations are relevant not only in product development and quality assessment but also in everyday life. Vibrations can be classified into desired ones — for example, those that provide user feedback to enhance the operation or user experience — and unwanted or even hazardous vibrations. Therefore, understanding the generation, transmission, and radiation of structure-borne sound is crucial.

In the field of vibroacoustics, we offer a variety of measurement and solution approaches tailored to these challenges.

We perform structure-borne sound measurements on your components or assemblies, customized to your specific requirements. This includes measuring accelerations on the components, transmission paths, and radiation behavior using advanced vibroacoustic measurement technology.

To investigate the radiation and transmission characteristics of components, we conduct vibration mode analyses. This process identifies both the natural frequencies and vibration modes of the components.

Based on the measurement results, we provide you with a tailored set of optimization measures to improve the vibroacoustic behavior of your components and achieve the desired performance.

Measurements are performed using high-quality accelerometers and force sensors. With a wide range of sensor models, we can cover the entire relevant frequency spectrum. For data acquisition and evaluation, we use the PAK system from Müller-BBM. Our measurement technology meets the highest standards for accuracy. Results are either determined according to standards or based on a customized concept developed in coordination with you.

When investigating components and parts, knowledge of the vibroacoustic behavior of the component on the one hand, and the transmission behavior on the other hand, is essential to adapt the development of the components to the installation situation.

We offer innovative measurement concepts specifically in the field of component and part analysis.

To measure the contact forces in (sub-)systems, we create a measurement chain based on the blocked-force method to determine all relevant interface forces. Alternatively, interface forces can also be determined using in-situ blocked forces.

To determine the material properties and transmission behavior of flexible bending components, we offer structure-borne sound measurements to identify the relevant parameters. The measurements can also be conducted in a climate chamber to account for temperature influences. Additionally, the internal pressure of fluid lines can be integrated into the measurement series to investigate the pressure influence of the medium on structure-borne sound transmission.

The measurements are carried out with high-quality acceleration and force sensors. Through a wide selection of sensor models, we can cover the entire relevant frequency range. For data acquisition and evaluation, we use the PAK system from Müller-BBM. Our measurement technology meets the highest Requirements regarding the accuracy of the measurement results. The blocked-forces test bench setup is tailored to your components to ensure compliance with the blocked-forces condition. Using our climate chamber, measurements under temperature influence from -40° to +180° can also be performed for small and medium-sized components. For the investigation of fluid lines, we also offer the possibility to examine static internal pressures of the line up to 40 bar.

Then you’re exactly right with us. If needed, we design a concept for your drive that is optimized both in control technology and acoustics. We’re also happy to optimize existing control systems for you. To operate a drive acoustically optimized, a lot of groundwork can already be done in the control system, starting with the control concept. We design or optimize this for you and coordinate the drive concept acoustically in parallel. Additionally, using our algorithms, beyond the normal function, we can overlay sounds, noises, or sound concepts specified by you, effectively using the drive as a speaker. We also work on active noise cancellation, which can, depending on the setup, be implemented with the drive and an optimally designed control system. This way, the drive can fulfill its intended task and additionally serve as a speaker or exciter, or eliminate certain disturbing noises that occur.
With our software MXsounddesigner, we can also create sound design concepts for the sound of e-vehicles or e-motors of all kinds.

First, the control concept for the intended operation of the drive is developed. Simultaneously, the acoustic sound of the drive is measured, analyzed, and optimized using structure-borne and airborne sound technology. Once the acoustically optimized drive concept is fully functional, additional algorithms can be integrated to either generate extra sound or reduce unwanted noise. The development work is carried out with state-of-the-art measurement technology. For the control concept, dspace real-time hardware is used, and for the acoustic optimization, class 1 microphones and high-quality accelerometers are employed, with their signals captured by a PAK system from Müller-BBM.

In the field of vehicle acoustics, the acoustic quality impression plays an important role. on one hand, the airborne noise affecting the driver and passengers is significant, and on the other hand, the vibrations transmitted into the vehicle interior also matter. unwanted noises should be minimized as much as possible, while at the same time, a high-quality vehicle sound that the customer can identify with should be created. the same applies to the vibrations that occur. the driver wants to receive tangible feedback from the road surface, but driving and seating comfort should not suffer. this is where we can support you.

Thanks to our long-standing close ties to the automotive industry, we can draw on a broad knowledge base in the fields of vehicle acoustics and driving comfort.

To identify noise phenomena at the whole-vehicle level, we perform airborne sound measurements inside the vehicle. From these measurements, noticeable components are identified and evaluated, and improvement suggestions are derived.

As a counterpart to airborne sound, we also offer structure-borne sound investigations on the entire vehicle. Here, the focus is placed on driving comfort. the complete vehicle is measured, and any influencing components are identified and evaluated, with improvement suggestions developed as needed.

Thanks to our wide range of sensors designed for different frequency ranges and measurement conditions, we can cover all relevant components and measurement scenarios. For driving components, triaxial accelerometers are mounted, for example, on the wheel carrier. On the seat rail, MEMS acceleration sensors can be installed to capture the low-frequency range relevant to driving comfort. Additionally, vibrations directly on the seat surface can be recorded using seat cushion vibration sensors. This also allows for normative measurements to be offered. The airborne noise inside the vehicle is measured using class 1 microphones. For data acquisition and evaluation, we use the PAK system from Müller-BBM. Our measurement technology meets the highest requirements regarding the accuracy of measurement results. The results are either determined according to standards or based on customer-specific KPIs or evaluation methods.

The acoustic quality of an electric machine often depends on its operating condition and design. To investigate these interactions and improve the sound experience for the user or operator, it is beneficial to measure both the electrical and acoustic parameters in order to assess the relationships.

Through our many years of expertise in controlling electric machines and the associated connection to the airborne sound emitted by the machine, we can support you in determining the acoustic properties and optimizing your electric machine. For this purpose, we perform time-synchronized and highly precise measurements of the voltages, currents, and power flows, as well as the acoustic and control-related parameters.

The measurement of electrical quantities is carried out using a Dewetron Power Analyzer, which is synchronized with our PAK system from Müller-BBM via a PTP switch. This enables high-resolution and highly accurate measurement of electrical parameters in the MHz range, simultaneously with the air-borne and structure-borne sound measurements conducted using class 1 microphones and high-quality acceleration sensors.

Acoustic problems often arise from structural excitation, such as unfavorable natural frequencies, local resonance phenomena, or insufficient stiffness. More flexible structures like cables are particularly susceptible and difficult to assess.

We support you with structural mechanics simulations to precisely analyze the acoustic behavior of your components. This can be offered as a standalone service or combined with experimental measurements. Through modal analyses, we identify critical natural frequencies and evaluate vibration behavior. From this, we derive targeted measures such as frequency shifting, stiffening, or structural decoupling.

A key advantage lies in linking simulation and measurement. We measure the transfer behavior experimentally while simultaneously creating an FE model. This model is calibrated and validated using the measurement data. This results in a digital twin that can be used for further optimizations without needing to measure anew in each iteration. This saves you time, reduces testing costs, and provides reliable early insights into the acoustic behavior.

For evaluating the acoustic structural behavior, we rely on Finite Element Analyses (FEA). The focus is on modal analyses to determine natural frequencies and mode shapes, complemented by simulations of harmonic excitation to assess the structural response under specific load cases.

Optionally, we combine the simulation with experimental measurement data, collected by us upon request. A parallel simulation model is created and calibrated and validated based on measured parameters such as dynamic stiffness and damping. Validation is performed, for example, by comparing transfer functions and using the Mode Assurance Criterion (MAC) to ensure reliable agreement between simulation and reality. This digital twin can then be used for parameter studies and targeted optimizations.

Depending on the question, we perform full natural frequency analyses, parameter studies, sensitivity analyses, or accompanying models for the acoustic design of complex structures — precisely tailored to your requirements.