MTG Test & Measurement highlights at Automotive Testing Europe 2023 in Stuttgart

MTG was pleased about the great interest in the traditional Test & Measurement portfolio as well as in newly developed products.

This year’s MTG highlights included enhanced in- and outdoor measurement microphones, digital preamplifiers, sound intensity probes, acoustic calbrators, turnkey in- and outdoor test benches as well as  the optimised Sound Power Hemispheres SLH for measurements according to ISO 3744 and ISO 3745 for various applications in R&D, sound design and consumer protection.

NEW – WME 980 as digital version in addition to the weatherproof microphone units WME 980 AM and WME 980 CN

MTG traditionally offers a wide range of precision measuring microphones with weather protection for temporary and permanent installations.

The WME 980 AM and WME 980 CN are high-end weatherproof microphone units for permanent outdoor measurement as well as stationary or mobile community-noise monitoring or airport noise.

• 20 Hz to 20 KHz
• 15 dB(A) to 146 dB
• Lemo® ERD.2S.306
• Power supply: 6 to 25 V DC
• remote calibration with electrostatic actuator
• suitable for sound level meters of Type 1 acc. IEC 61672

Inside the housing there are switches for the cable driver and the microphone heater, which prevents condensation under extreme climatic conditions..

The digital version consists of the 1/2" measurement microphone capsule MKS 221, the 1/2" measuring microphone preamplifier MV 240 digital with USB interface, a dry adapter, a rain/dust protection and a wind protection with bird deflector.

MV 240 digital – New fields of application in weatherproof microphones and positive customer response

 The innovative MV 240 digital is an all-in-one development which differs in every respect from all commercially available analogue digital solutions in terms of design and quality.

The outstanding features include, for example:

– Digital measuring microphone with 32-bit data transmission

– Digital transmission of fixed calibrated sound pressure values

– Full dynamics of a newly developed low noise 1/2" capsule   

– With "¼" capsule – maximum 160 dB sound pressure level

– max. dynamic range of the 32 bit range is 186 dB

Equipped with a new, specially developed high-end low noise capsule and a new, integrated electronic system (including an integrated AD converter/ADC) that is tuned to the microphone capsules, the MV 240 considerably expands the circle of potential users.

Existing disadvantages of previous AD solutions with regard to costly operation and time-consuming installation, possible sources of error due to complicated coordination of several electronic components and the resulting time and personnel expenditure could be overcome.

The new MV 240 offers the possibility of solving all the above-mentioned problems with just one device, thus saving time and money, i.e. it cost-savingly replaces 2 analog measurement microphones, two analog front end channels and a part of the digital signal processing.

In addition, no separate power supply unit is required as is usually the case with analog measurement microphones when their full dynamic range is to be used. 

Another major advantages are a test generator integrated into the microphone, which checks both the complete transmission and evaluation of a 32-bit data stream from the microphone via the interface to the measurement software on the PC and the possibility of using common measuring software, compatible with all common operating systems

The new MMS 214 1/2" and 212 1/2" measurement microphones

 The growing demand confirms the ambition of the MTG R&D department to develop measurement microphones for extreme operating conditions and particularly demanding measurement tasks.

MMS 214 1/2“ Measurement Microphone with particularly low inherent noise level

• free-field, 2 Hz to 20 kHz, 6,5 dBA to 104 dB
• IEPE (BNC)
• Microphone power supply: IEPE
• TEDS acc. IEEE 1451

The MMS 214 is designed for acoustic measurements of low sound pressure levels close to the threshold of human hearing. The microphone preamplifier internally generatesthe polarization voltage for the externally polarized microphone capsule.

MMS 212 1/2“ Measurement Microphone for rugged environment

 free-field, 3,5 Hz to 20 kHz, 15 dBA to 139 dB

• IEPE (BNC)
• Microphone power supply: IEPE
• TEDS acc. IEEE 1451

The MMS 212 is very insensitive to extreme temperature, humidity, dust and vibration and therefore designed for applications in rugged environments. It can be calibrated with a standard 1/2“ sound calibrator.

The measurement microphone is suitable for sound level meters of IEC class 1 acc. IEC 61672.

Of growing importance -localization of sound sources using 3D sound intensity probes

The localization of sound sources using three-dimensional sound intensity probes / SIS has already been gaining importance for several years, such as for applications on robots in the automotive industry.

For this reason, MTG places particular emphasis on the development and manufacture of an extensive range of sound intensity probes.

The highlights include the SIS 194 3D 1/2" and SIS 194 3D 1/4"

The SIS 194 3D allows a simultaneous sound intensity measurement at one point of a room in all three dimensions. For this purpose an arrangement of three one-dimensional sound intensity probes is formed, thus all three axes of the microphone pairs cross in one point and are in a plane perpendicular in each case.

Each of those microphone pairs constitutes a one-dimensional sound intensity probe in conventional design.

In addition to measurement of sound pressure, each individual sound intensity probe -by its two-microphone-technology – enables the acquisition of the sound pressure gradient and thus the sound intensity computation.

The quality of conformity of both measurement capsules, relating to their transfer function, is measured in accordance with DIN EN 61043 and IEC 1043 respectively and documented as pressure-intensity-distance/residual-intensity-distance for probes. To each measurement-capsule pair of the SIS 194 3D a measurement report is enclosed. On the basis of this report the compliance with tolerance limits for class 1 probes is apparent.

SIS 194 3D 1/2”  

• 35 Hz to 1.5 kHz
• 12-pin Lemo®
• Microphone power supply: IEPE

The SIS 194 3D 1/2" consists of three Measuring Microphone Capsules Pairs MK 290 E (2x MK 222 E) with matched phase response and frequency response. Due to the use of the 1/4” Measuring Microphone Preamplifiers MV 310, sound field distortions (shadowing and diffractions) are minimal. The distance between the microphone pairs is defined by spacers (50 mm). These enable measurements in a frequency range between 35 Hz and 1,5 kHz.

SIS 194 3D 1/4” 

• 1 Hz to 10 kHz
• 12-pin Lemo®
• Microphone power supply: IEPE

The probe consists of two in phase- and frequency response matched measurement-microphone capsules MK 222 E (order drawing MK 290 E) and MK 301 E (order drawing MK 390 E). By the use of the constant current powered 1/4 ‘’ measurement-preamplifier MV 310 the sound field distortions (shading and diffraction) are minimal. The distance between the three microphone capsules is accurately defined by means of a spacer. Thereby measurements are possible in a frequency range from 35 Hz to 10 kHz.

SIS 190 double – Measurements without Interruption

The SIS 190 double allows a simultaneous sound intensity measurement in a very large frequency range.

• 35 Hz to 12 kHz
• 10-pin Lemo®
• Microphone power supply: IEPE

For this purpose an arrangement of one one-dimensional 1/2" sound intensity probe and one one-dimensional 1/4" sound intensity probe is formed. Due to its two-channel technology each individual Sound Intensity Probe makes it possible not only to measure sound pressure levels but also to record the sound pressure gradient which is needed to calculate the sound intensity.

The SIS 190 double consists of the Measuring Microphone Capsules Pairs MK 290 E (2x MK 222 E) and MK 390 E (2x MK 301 E) with matched phase response and frequency response.

Due to the use of the 1/4” Measuring Microphone Preamplifiers MV 310, sound field distortions (shadowing and diffractions) are minimal.

The quality of conformance between the microphone pairs with regard to their transforming functions is measured in compliance with DIN EN 61043 and documented as Minimum pressure-residual intensity index for probes.

Each microphone capsule pair comes with a measuring protocol. It shows the tolerance limits for class 1 probes.

DAkkS Certificates- Increased demand for calibration services according to the latest global standard DIN EN ISO/IEC 17025:2018

The accreditation of conformity assessment bodies (laboratories, inspection and certification bodies) is the legal mandate of the German Accreditation Body (DAkkS).

The result of the successful audit was the confirmation of the existing DAkkS accreditation and the competence as DAkkS-accredited testing laboratory in an annex to the accreditation certificate D-K-19573-01-00 according to DIN EN ISO/IEC 17025:2018 for Mechanical measurands – Acceleration and Acoustic measured variables

MTG calibrates the physical parameters sound pressure and acceleration in its own laboratory and issues either DAkkS- or factory certificates (optional).

The measuring standards for sound pressure and reference microphones are traceable to PTB standards / Physikalisch Technische Bundesanstalt.

The measuring standards for acceleration and reference acceleration sensors are traceable to DKD standards (Deutscher Kalibrierdienst).

Acoustic calibrators from Gefell – Sound Calibrator 4010 and Sound Calibrator 4011

The 4010 is a sound calibrator conforming to IEC 60942 class 1 and ANSI S1.40 for the calibration and the verification of microphones and sound level meters.

The combination of two sound pressure levels and two frequencies allow both level linearity and frequency linearity to be verified.

Each sound calibrator is supplied with an individual calibration certificate.

The reference microphone and control circuit together maintain a constant sound pressure level inside the calibration coupler and automatically adjust for changes in load volume, temperature, atmospheric pressure and relative humidity.

In addition the sound calibrator measures the environmental conditions temperature, atmospheric pressure and relative humidity.

The 4011 is a sound calibrator conforming to IEC 60942 class 1 and ANSI S1.40 for the calibration and the verification of microphones and sound level meters. It generates a sound pressure level of 114 dB at a frequency of 1000 Hz for the verification of the calibration of sound level meters. Each sound calibrator is supplied with an individual calibration certificate.

The reference microphone and control circuit together maintain a constant sound pressure level inside the calibration coupler and automatically adjust for changes in load volume, temperature, atmospheric pressure and relative humidity. The sound calibrator can be used for 1/2“ and 1/4“ microphones.

Optimised Sound Power Hemispheres / SLH  for sound power measurements according to ISO 3744 and ISO 3745

Internationally, manufacturers of all sound-emitting industrial and consumer goods devices are increasingly required by law to record and comply with the entire chain of human and environmentally relevant sound emissions.

At the same time, consumer-oriented sound design is becoming increasingly important in product development, e.g. designing corporate and brand product sounds in the field of e-mobility in the automotive sector.

The necessary analyses can only be carried out using powerful measuring and testing technology.

So-called enveloping surface methods are essential here, which enable measurements on measurement objects placed under a dome by means of sound power hemispheres, among other things.

The sound power emitted by a noise source is measured at defined, statistically uniformly distributed measuring points on a dome-shaped measuring surface enclosing the source. The microphone/sensor positioning is done according to sound power standards 3744 and 3745.

The SLH can be installed with 6 or 12 bars and allows to use 10 or 20 pieces of high standard measurement microphones conform to DIN IEC 61094-4.

The same microphone arrangement can be used, e.g., in a perfect application to record the sound of components of electrical vehicles. Another application for sound investigation of acoustical components by using of hemispherical microphone arrangements is measurement of tire noise

The new sound power hemisphers are a "one for all" solutions for a wide range of measurement tasks, including the optional selection of suitable sensors from other manufacturers.

A unique feature in terms of flexibility is the possibility to cover all relevant frequency ranges (DIN EN ISO 3745:2017-10 / "General case").

Outstanding features of all new MTG-SLH-Models are user-optimised design, increased precision, extended functionality, application range and flexibility.

The innovative design ensures optimal, stable sensor positioning, cost-effective, simplified mounting and measurement procedures, and, last but not least, reproducible measurement data in accordance with international standards.

A standard-compliant, geometrically exact alignment to the centre is possible without the use of additional measuring/adjustment equipment.

The SLH are available in two different sizes for the buildup of hemispherical microphone arrays with radii of one or two meters for up to 20 microphone positions each. Depending on the measurement task, the sound power hemispheres can be supplied with standard measurement microphones, particularly low-noise measurement microphones or measurement microphones for harsh environments.

Microtech Gefell -Turnkey in- and outdoor test benches

Exterior and interior noise measurements are of increasing importance for the vehicle development as well as in the production-side quality assurance and are decisive for the type approval or the product sound design.

In order to obtain a type approval for vehicles as a precondition for the sale in different markets, it is required, among other things, to carry out a type test, e.g. according to standard ISO 362-1:2015, to meet the acoustic requirements.

For this purpose, a special driving cycle is executed on a defined measuring section.

Microtech Gefell has long-time experience in planning and installing the necessary outdoor pass-by or indoor simulation measuring sections.

A special acoustic measuring system, different control signals such as light barriers, speed measuring system, GPS (if any), climate data recording and road temperature measurement are integrated into the system.

They are implemented by means of installation-related planning as well as performance for fixed installations of pass-by test stands under field conditions.

Weatherproof microphones from MTG’s product range are used for permanently installed systems. Together with the used sound level measuring system, they form a sound level measuring chain which is used for checking the standard values and, simultaneously, for the frequency-related analysis of the driving noise.

Microtech Gefell -Turnkey indoor solutions – Simulation test benches

Microtech Gefell also has extensive experience in planning and installing such test stands and is able to integrate the components necessary in addition to the measuring system. The structural and building-related work, e.g. acoustic room setup and drive systems, is coordinated for the projects by Microtech Gefell, but it is not included in the company’s scope of work.

Furthermore, the MTG team plans and installs the metrological components in any kind of acoustic and vibration test stands such as sound measuring rooms with chassis dynamometers, modal analysis and hydro pulse systems.