Sound Quality and Vehicle Condition
For more than a decade, evaluation of sound quality inside trams has been done by Tramwaje Warszawskie sp. z o.o., (Warsaw Tramways Ltd.) in cooperation with Brüel & Kjær Polska Sp. z o.o.
The evaluations were done using binaural recordings made on a number of trams manufactured between 1908 and 2008, travelling on normal town routes.
Until recently, a Head and Torso Simulator (HATS) and instrumentation recorder would be used, for example a PULSE system. This usually required a vehicle to be removed from service. This is inconvenient, but the information that a good recording conveys could also be used for troubleshooting and maintenance work as well and sound quality and comfort.
In 2008 Brüel & Kjær introduced the SoNoScout system to the automotive industry and this has proven to be ideal for collecting data “in real time” – that is, by an engineer travelling as a passenger on a tram in normal service.
SQ Recording the Easy Way
With SoNoScout, the drawback of taking vehicles out of service, complicated setups, and the considerable cost of traditional SQ recording and analysis systems was no longer a problem. The self-contained PDA-based SoNoScout NVH Binaural Recording and Analysis System could be taken for a tram ride, just like any other PDA/Mp3 player.
SoNoScout features the functionality of a HATS and comprises an extremely easy to use, handy recorder and a sound-card to interface to measurement microphones. The system offers high-quality, calibrated, binaural recordings, along with GPS data indicating the vehicle position and speed. Data acquisition can be performed by anybody on a vehicle in regular service.
Operating the touch screen of the pocket PC, the operator only needs to establish the GPS signal, choose a name for the file and press start.
During recording, the operator wears standard mini headphones with built-on microphones positioned close to his ears. This results in a binaural recording, saved as a wave file, along with position and speed information. By appearing as a normal traveller “listening to music”, the operator avoids unwanted attention from passengers or the driver, thus making the recordings very realistic.
The wave files gathered can be used for analysis and post-processing using Brüel & Kjær’s PULSE software.
The software running in the pocket PC enables you to:
- Play back the sound
- Show the sound levels vs. time, as well as FFT and CPB spectra
- Plot the contour in 3D
- Filter the signals and play them filtered
- Track the RPM
- Plot the route and vehicle speed
The sound signal can be played back and analysed together with the GPS data, and features a live cursor moving over the time and spectral plot. The same kind of analysis can be performed in the handy recording device and the PC software provided.
Furthermore, the data can be analysed using more advanced tools such as the PULSE data acquisition and analysis system.
The design, operation and maintenance of streetcars is of interest to manufacturers, operators and consultants.
We asked an example of each to evaluate SoNoScout:
- The Manufacturer: Pojazdy Szynowe Pesa Bydgoszcz SA – a Polish company manufacturing rail vehicles, including fully low floor articulated streetcars
- The Consultant: The Department of Intelligent Technologies at the Institute of Fundamental Technological Research, Polish Academy of Sciences, known as IPPT PAN – a recognised scientific and research centre offering high-quality NVH and SQ testing and troubleshooting for the automotive, railway, machine diagnostics, and aerospace industries
- The Operator: Tramwaje Warszawskie sp. z o.o. – a company operating trams in Warsaw and who pay considerable attention to environmental issues and travel comfort
The extensive tests led to the same opinion – SoNoScout is a very versatile, cost-effective and useful tool. High-quality, exchangeable data, ease of use, immediate result presentation and the ability to perform measurements during normal operation, even by a non-skilled person, were especially appreciated.
All three evaluated SoNoScout as especially suitable for the following:
- Transferring “hot” data to the consultant or designer
- Easy data collection for archiving and periodical trend analysis
- Product marketing and benchmarking, including real life examples
- Communicating quality problems or specification requirements to sub-suppliers
- “Before and after” comparisons for vehicles under maintenance/overhaul
- Studying vehicle dynamics, including normal load
- Developing, selecting and adjusting broadcast systems, warning signals and aids for blind people, etc.
So, who knows, the next time you take a tram ride you might be riding alongside SoNoScout.