With decades of experience in the complex world of acoustic measurement and data acquisition, our guest today is a leading expert in vehicle testing and certification. They have been at the forefront of deploying sophisticated measurement solutions, like those from imc Test & Measurement, to help major manufacturers such as Stadler Rail ensure their vehicles are not only compliant with strict regulations but also deliver a superior passenger experience.
This conversation delves into the critical importance of conducting acoustic tests under real-world operating conditions and the unique technological challenges this presents. We will explore how the synergy between advanced data acquisition systems and high-precision microphones provides the high-quality data necessary for both certification and design optimization. Furthermore, we’ll discuss how this detailed acoustic information is translated into tangible improvements in passenger comfort and perceived safety, moving beyond simple noise limits to refine the entire rider experience. The discussion also sheds light on the process of transforming raw data into actionable insights that guide the validation and improvement of modern rail vehicles.
You performed tests on Stadler’s vehicles under real operating conditions. Why is this approach so critical for both regulatory compliance and passenger comfort, and what unique challenges does it create for data acquisition compared to a controlled environment? Please provide a specific example.
Testing directly on the vehicle in its natural environment is absolutely essential because both regulations and passengers exist in the real world, not a sterile lab. In a controlled setting, you can eliminate variables, but you also eliminate reality. The goal is to understand the vehicle’s true acoustic signature, which includes how it interacts with different track conditions, weather, and operational demands. This is critical for certification, as regulators need to know the vehicle meets noise limits during typical service. For passengers, a constant, low-level hum that’s acceptable in a lab might become an irritating rattle when combined with the vibrations of a real track. The biggest challenge for data acquisition is filtering out the signal from the noise—literally. Our systems must be robust enough to withstand the vibrations and environmental factors of a moving train while being sensitive enough to capture the nuanced sounds we need. For instance, capturing the precise acoustic profile of the braking system as the train enters a station, with ambient city noise in the background, is far more complex and valuable than testing the brakes in a quiet, stationary test bay.
The combination of imc data acquisition systems and GRAS microphones was key to collecting high-quality data. Can you walk me through how these two technologies integrate during a typical test and what specific advantages this setup offers for vehicle certification and optimization?
Think of it as a nervous system for the vehicle. The GRAS measurement microphones are the highly sensitive nerve endings, placed strategically throughout the vehicle—in the passenger cabin, near the bogies, and outside—to capture sound with incredible accuracy. These microphones convert acoustic waves into precise electrical signals. The imc data acquisition system then acts as the central brain. It takes all these disparate analog signals and digitizes them simultaneously. The magic of the imc system is its ability to synchronize this acoustic data with other vehicle parameters, like speed, acceleration, and braking pressure. This integration is the key advantage. It allows us to create a complete, multi-layered picture of an event. We don’t just hear a loud noise; we see that it occurred at exactly 85 km/h as the train entered a specific curve. This direct correlation between cause and effect is invaluable for engineers, allowing them to pinpoint a problem and develop a targeted solution, which is fundamental for both passing certification and truly optimizing the vehicle.
Beyond simply meeting regulatory noise limits, how does the detailed acoustic data you collect translate into tangible improvements in passenger comfort and perceived safety? Could you share an anecdote or metric where a minor acoustic adjustment made a significant difference for the rider experience?
Meeting regulatory limits is just the entry ticket; true excellence lies in shaping the passenger’s sensory experience. The data we collect allows us to dissect the soundscape inside the cabin. We’re not just looking at the overall decibel level; we’re analyzing the frequency and character of different sounds. Is there a high-pitched, intermittent whine from the HVAC system? A low-frequency rumble from the wheels? These are the things that don’t necessarily break regulations but can create a fatiguing or unsettling environment for passengers. A quieter cabin is often perceived as a safer, higher-quality vehicle. I recall a project where we identified a specific harmonic vibration that occurred only at cruising speed, creating a subtle but persistent buzzing sound near the windows. While well within legal limits, our analysis showed it was right in a frequency range that is particularly annoying to the human ear. By providing Stadler’s engineers with this precise data, they were able to add a small amount of targeted damping material. The overall decibel level barely changed, but the character of the sound was transformed, leading to a noticeably more serene and premium-feeling ride.
After collecting the raw acoustic data, what is the process for turning it into actionable insights for a client like Stadler Rail? Could you describe the key steps your team takes to help them validate prototypes, optimize products, and improve the overall vehicle design?
The raw data is like a massive, unread library; our job is to find the right books and interpret them. The first step is data processing and validation, where we clean the signals and filter out any irrelevant environmental noise. Next, we move to analysis. Using specialized software linked to the imc systems, we correlate the acoustic events with the vehicle’s operational data. We generate detailed reports with visualizations—like spectrograms that show noise frequency over time—which make it easy to see where and when specific acoustic issues arise. For a prototype, this process helps validate that the initial design meets its acoustic targets. For an existing product, it’s about optimization. We might identify that a certain panel is vibrating and causing a rattle at a specific speed. We then provide this focused insight to the engineering team. This allows them to move from a vague complaint like “it’s too noisy” to a specific, solvable problem, enabling them to make targeted design changes, test them, and use our follow-up measurements to confirm the improvement.
What is your forecast for the future of acoustic testing in the rail industry?
I foresee a significant shift towards more integrated and continuous monitoring. Instead of just performing acoustic tests for certification at a single point in time, we will see more systems embedded for the life of the vehicle. This will allow for real-time monitoring of the vehicle’s acoustic health, predicting maintenance needs before they become critical failures—for instance, detecting a change in a wheel bearing’s sound signature long before it fails. Furthermore, the focus on the subjective passenger experience will intensify. We will move beyond simple decibel measurements to more sophisticated psychoacoustic models that can predict how “annoying” or “pleasant” a soundscape is. This will enable manufacturers to not just build quieter trains, but to actively design a more comfortable and reassuring auditory environment for everyone on board.
