Haptic and acoustic performance: Switches at the heart of the automotive industry

In the past, the electrical items used in automobiles were mainly lights, heaters and wipers that were activated with relatively simple switches, most of them toggles that could be sourced from a few manufacturers. The interior of these classic autos was simple yet functional.

Recently, the trend has been to include more complex features (such as infotainment) and the aesthetics and ergonomics of interior controls became more important in the switch selection, mainly through the layout of the various controls. Manufacturers are focusing on the look and feel of the passenger cabin and searching for ways to differentiate their offerings in an increasingly competitive business.

As a result, the design process for automotive interiors and controls now revolves around haptics, defined as the science and physiology of the human sense
 of touch, and acoustics, defined as the science of audible sound perception. The brand identity of a vehicle and its position within the range of automobiles from a manufacturer is characterized by the look, feel and sound, and these key elements mainly rely on the switch quality.

From robust pushbutton or toggle switches with relatively long travel, automotive interior subsystems and user preferences have evolved to more modern switches, such as smaller tactile switches with much shorter travel (less than 0.8 mm). With the increase of switches in the dashboard, smaller switches are required to fit within the available space. Many of today’s drivers perceive old-style “long-travel” switches to be of inferior quality because they are familiar with the interface of portable devices such as smartphones. Short-travel switches are usually based on a metallic “snap” dome contact system that interfaces between the actuator and the switch housing.

Nowadays, automotive manufacturers and their suppliers producing subsystems such as switch panels often produce detailed specifications for the haptic and acoustic performance of the switches they select to ensure that they meet the brand identity as well as delivering consistency over time. For switch manufacturers, delivering correct and consistent acoustic performance to produce a sound and feel that match the required perception of brand quality desired by the automaker is the biggest challenge.

Several elements enter into the composition of a tactile switch and define the sound it makes. For example, the dome material and composition, structure and design of the switch body, and how the switch fits into the larger system impact the final product. So tuning switches can be a bit of an art and requires experience to deliver the correct results.

Characterizing the acoustics of any switch usually involves measuring the audible spectral components of the sound made, using an accurate sound meter in a carefully controlled environment. The spectral distribution describes the sound’s “colour” and clearly differentiates between the two distinct sounds generated by the switch’s actuation and release.

Every component of the switch structure has an impact on the sound of the switch and must be carefully considered and tweaked to deliver the required sound spectrum.  Embedding the switch in a printed circuit board can also change the sound of the switch, as can fitting the sub-assembly into the vehicle, so switch manufacturers have to work in close coordination with the vehicle manufacturer to ensure that the switch performs as desired in the vehicle.

C&K, a leading manufacturer of high-quality electromechanical switches, has extensive experience in customizing short-travel tactile switches such as the KSC series and has an extremely wide range of components to draw upon. C&K has also invested in a state-of-the-art anechoic chamber with an accurate sound evaluation that enables evaluation of individual switches and customer sub-assemblies. It offers reliable and high-performance switches with just the right sound and feel.