Acoustical Measurement and DSP Application in Automotive Audio

This article offers a primer on how to approach acoustic measurements and the practical application of DSP in car cabins, one of the hardest acoustic environments for quality sound reproduction. The topics addressed in this article will be expanded in future articles.

- Philipp Paul Klose

Car cabins are one of the hardest acoustic environments to create quality sound reproduction in: The space is small and has massive room resonances from the deepest bass notes up until the midrange frequency band. Acoustic engineers are confronted with surfaces that either create nasty reflections (e.g., glass or metal), while other parts are covered with effective acoustic dampening materials (e.g., Thinsulate or Basotect), and are therefore very absorptive. At the joints of interconnected materials rattle noise can occur.

The speakers can only in a few cases be directed at the listeners at the 0° axis and the car is producing noise by itself through flowing wind, rumbling tires, and a working powertrain be it electric or of an internal combustion type. It seems like the only good thing is that we know where the listeners ears are positioned and that they will barely move their heads.

Although it is possible to have good sound reproduction in the car: It is just a little bit harder to attain than in other environments. Thankfully, DSP power is available, and it is more than useful in cars. While tuning often seems like a black art and is feared by many engineers, much like an exam in higher mathematics, it is not that complicated.

Proven measurement techniques help substantially with achieving a good tuned system and mastering the many tasks that can be also done by engineers who are not blessed with "golden ears."