Harman Kardon® in Vehicles
Virtual acoustic technologies including complex testing and measurement processes: a high-precision approach for perfect sound
Work on a tailor-made sound system begins long before a new car physically exists, even in prototype form. The acoustic engineers start with the development as soon as first design studies of a new car have been defined. Fine-tuning can take up to three years because the final car profile, equipment and material properties can change during development phase. Complex computer-simulation technology and detailed tests are used to perfect the sound profiles in each new model.
The acoustic experts make use of the VirAx (Virtual Acoustics) tools specially developed by HARMAN for this purpose. The virtual-development environment allows the acoustic properties of the vehicle interior to be displayed in three dimensions, with music made visible on the screen. All factors that affect the sound in the interior, however minimally, are taken into account. These include, for example, trim panels or windows that vibrate along with the system, causing resonances that interfere with the sound. The simulation allows Harman Kardon engineers to determine the distribution of the sound right into the furthest corner of the interior. To optimize the sound, the loudspeakers can be placed at various positions in the future car using the virtual computer model. The optimum diameter is also defined so as to create the best possible sound. Different-colored areas on the screen show development engineers where the acoustic pressure is particularly high or guide them in eliminating problems. There may be areas within the complex architecture of the vehicle interior in which sound waves cancel each other out. Thus, there are numerous steps along the way in determining how each of the 10, 12 or even 14 loudspeakers should be positioned for optimum effect. Naturally, close cooperation with the car manufacturers is essential every step of the way so that the best possible combination is found.
However, the virtual-development environment is not just limited to the graphical reproduction of the acoustics. You can also listen to the virtual sound system. A binaural reproduction technique allows acoustic engineers to listen to the as-yet-nonexistent car, enabling them to carry out auditory tests to further refine the sound.
Once the optimum position for the loudspeakers has been defined and the corresponding high-quality components have been developed and selected, extensive tests and measurements are carried out for the perfect sound.
Harman Kardon, Inc., subjects all sound-system components to extreme tests – similar to the tests undergone by the car itself – in order to test their resilience in practice. The components are required to withstand demanding extreme-temperature tests, as well as unusual vibration stresses, to ensure long-term quality.
A microphone array with six precision measuring microphones is used in the Harman Kardon development laboratory to measure frequency response. The mobile frame construction can be positioned individually at all seats inside the test vehicle, permitting maximum precision. This enables Harman Kardon engineers to achieve absolute neutrality, as well as the required faithful reproduction quality, in the sound system.
When a new Harman Kardon sound system has passed all the tests involved through modern measurement technology and scientific evaluation processes, it must undergo one final test: the human ear. After the simulation tests on the virtual model, top acoustic experts employ detailed and direct audio comparisons. “The human ear remains the most precise measuring instrument,” explains founder Dr. Sidney Harman. These tests are first performed step-by-step in the laboratory and then in the finished car. The final sound must always match high Harman Kardon standards but may feature fine nuances, depending on the particular car model and the relevant target group. Only if the “golden ears” of the Harman Kardon acoustic experts are truly convinced of the quality of the reproduction will the premium sound system be allowed to be used on the road.