A handy and multi-purpose tool, LMS Test.Lab Virtual Car Sound can be used for general sound design and target-setting as well as advanced vibro-acoustic trouble-shooting in the vehicle refinement stage. The LMS Test.Lab Virtual Car Sound solution is mainly applied to vehicles, but can be helpful when analyzing issues found in other rotating machinery products and components.
Starting from experimental or CAE data, a sound quality equivalent model (SQE) is generated that decomposes the interior car noise into powertrain, road/tire, and wind noise.
This sound decomposition methodology has been tested and confirmed by a jury. The SQE model is equivalent in quality and features to the original sound. For troubleshooting and target-setting applications, the model can be refined with a TPA model to study the different structure-borne and airborne path contributions.
This virtual vehicle can be driven interactively under different operating conditions. Speed, rpm, throttle, gear and brake can be adjusted. While driving, users can listen to the generated sounds for a subjective evaluation. For objective evaluation and target-setting, FFT-based spectral analysis is complemented with real-time sound quality metrics, like loudness, articulation index and roughness. The partial contribution of the different sound sources and paths is also displayed in real-time. This interactive driving mode gives maximum freedom to the sound engineer to simulate realistic operation conditions. For more project flexibility, this mode comes with a drive-by-file mode for repeatable drive profiles and an external control mode. This could be a CAN-bus or serial port interface that provides the hook-up of an external vehicle simulator.
All model components – orders, octave bands, FRFs, accelerations, mounts, forces – can be modified in real-time for evaluation of ’what if’-scenarios. Modifications include peak removal, level increase/decrease, phase corrections, and randomized phasing. Click-free switching between modified models provides straightforward A/B comparison under any operating condition.
During the refinement stage, time is limited and one might only have limited data to build the model. LMS Test.Lab Virtual Car Sound has been designed with these situations in mind. Even with limited data, a SQE model can be created. LMS Test.Lab Virtual Car Sound can handle both monaural and binaural data.
The use of sound quality engineering tools in automotive development is well accepted - but their application is mainly restricted to the refinement and troubleshooting of physical prototypes. Currently, designers have few tools to help them listen to their ‘virtual’ models. Imagine what could be achieved if an awareness of sound quality could be implemented upfront. The concept team could use a joystick to listen to the engine note as it goes through an arbitrary speed change. 
Incorporating engineering attributes like external engine sound or ride comfort into the design cycle is nothing new for automotive engineers and especially NVH experts. What is new though is the role of the brand image in engineering the overall driving experience. Like any product today, automotive brands are no longer just status symbols; they have become value symbols and customers expect that a car lives up to its brand promises.
