Precise noise measurement in rail vehicles according to ISO 3381 with imc WAVE and imc FAMOS

The imc WAVE software offers a powerful platform for the acquisition and analysis of acoustic data and supports:

• Direct measurement with high-quality microphones from GRAS sound and vibrations
• Real-time data analysis and monitoring with imc measurement system imc ARGUSfit or
  imc CRONOSflex
• Automated processes for reproducible measurement campaigns
  https://www.imc-tm.com/products/measurement-software/imc-wave-nvh-analysis/noise
  https://www.imc-tm.com/products/measurement-software/imc-famos

Noise measurements in the interior of rail bound vehicles are carried out according to the specifications of ISO 3381. This international standard defines methods for measuring and evaluating interior noise to ensure that the acoustic conditions meet comfort and safety requirements. Microphones are placed at defined positions in the vehicle interior, such as seating and aisles.

ISO 3381 is applicable to various types of rail vehicles, including:

• high-speed trains
• passenger trains
• freight trains
• trams
• metros

Operating conditions

The measurements include various operational scenarios:

• Starting noise: noise emissions when starting the vehicle
• Driving noise: noise emissions at a constant speed
• Braking noise: noise emissions when braking
• Stationary noise: noise emissions at a standstill, e.g. from air conditioning systems or fans

The combination of imc WAVE and imc FAMOS provides you with a precise, standards-compliant and efficient solution for interior noise measurement according to ISO 3381.

Noise measurements in rail vehicles are carried out in accordance with the specifications of ISO 3381 to determine the sound level inside the vehicle under real operating conditions. The measurements are used to assess comfort, safety and noise reduction in accordance with standards.

Measuring software and data acquisition system :

imc WAVE is used for control and data acquisition of the acoustic data. The microphones are connected to an imc measurement system that records high-resolution audio data. The microphones are calibrated before the measurement to ensure accuracy.

The measurements are carried out under realistic operating conditions, e.g.:

• Standstill: Noise level in the vehicle with the engine switched off and on.
• Start-up: Acoustic evaluation during vehicle acceleration.
• Constant speed: Measurement at defined speeds on straight sections of roadway.
• Braking: Recording of the sound level during vehicle braking.
• Tunnels & bridges: Analysis of environmental influences on the noise level in the interior.

• Standardized acoustic testing in rail vehicles
• Simple and precise data acquisition with imc WAVE
• Automated analysis & reporting with imc FAMOS
• Flexible adaptation to different vehicle types and operating conditions
• Immediate availability of measurement results through real-time analysis and reporting

The high-quality microphones from GRAS – 46AE, 146AE and 246AE – are specially designed for precise acoustic measurements. They differ in their construction, possible uses and technical specifications. Here are their main advantages and differences:

GRAS 46AE – Classic 1/2” free-field microphone with preamplifier

Benefits:

• Precise free-field measurements for general acoustics and laboratory environments
• High sensitivity (50 mV/Pa) for detailed measurements even at low levels
• Low self-noise 17 dB(A), ideal for precise acoustic analysis
• IEPE compatibility, enabling easy integration into measurement systems

Applications:

• Noise measurements in the automotive industry and rail bound vehicles
• Acoustic tests in research and development
• Sound power measurements and standardized noise measurements

GRAS 146AE – Rugged 1/2” free-field microphone for harsh environments

Benefits:

• Extended temperature and humidity range, specially designed for outdoor use
• High long-term stability, even under difficult environmental conditions
• IEPE technology for easy system integration

• More robust against external influences, making it particularly suitable for outdoor measurements

Applications:

• Outdoor noise measurements in traffic and environmental acoustics
• Long-term monitoring of noise emissions
• Noise measurements in industrial environments

GRAS 246AE – High-precision 1/2” free-field microphone with preamplifier

Benefits:

• Precise free-field measurements for general acoustic applications and laboratory environments.
• Ideal for many measurement channels thanks to SYScheck2™ auto-calibration
• Ideal for long-term monitoring thanks to SYScheck2™ auto-calibration

Applications:

• Noise measurements in the automotive industry and rail bound vehicles
• Acoustic tests in research and development
• Sound power measurements and standardized noise measurements

Summary of differences:

Modern measurement systems for sound and vibration analysis must meet demanding requirements: Flexibility, precision and reliability are at the forefront. This is precisely where imc ARGUSfit comes in – a modular measurement system developed specifically for the challenges of acoustic and vibration technology.

With its compact design and modular architecture, the system can be customized to meet specific measurement requirements. Thanks to ICP-compatible inputs, imc ARGUSfit is ideal for connecting microphones and accelerometers – perfect for noise, vibration and harshness (NVH) applications in the rail industry.

Another advantage is the synchronous acquisition of high-frequency signals, which also enables a detailed analysis of dynamic processes. Whether structure-borne sound measurements, vibration analyses or running noise tests – imc ARGUSfit delivers precise and reproducible results.

In combination with the imc STUDIO and imc WAVE software, the user has a powerful tool not only for signal acquisition, but also for real-time analysis, visualization and reporting.

Summary:
imc ARGUSfit is a highly flexible and powerful system that is ideally suited for sound and vibration analysis – from mobile applications to complex test stands.

When it comes to demanding sound and vibration analysis, the modular imc CRONOSflex measurement system is a powerful solution for research, development and industrial applications. Thanks to its high flexibility, robustness and accuracy, it is ideally suited for applications in the field of NVH (noise, vibration, harshness) – whether in the vehicle, on the test bench or in the field.

imc CRONOSflex supports a wide range of sensor types, such as IEPE accelerometers, microphones or strain gauges, and offers sample rates of up to 100 kHz per channel. This allows even highly dynamic processes to be precisely recorded – whether for analyzing resonance behavior, structure-borne vibrations, structure-borne or airborne sound.

The system is completely modular: the modules can be mechanically and electrically connected via pluggable connectors or distributed decentrally via CAT5 cable. This enables a customized setup – from just a few to several hundred channels – without sacrificing mobility.

Summary:
With its high measurement accuracy, flexible expandability and robust construction, imc CRONOSflex is an ideal solution for professional sound and vibration analysis – from the laboratory to mobile applications in the field.