Lynnaire Johnston - Science helps create warning sounds

Tuesday, August 09, 2011 12:00 PM

Just how do engineers choose the various warning sounds in your vehicle? Turns out there is more to it than whatever takes their fancy at the time - with Ford engineers, anyway.

Ford's research shows certain types of alerts work better in certain situations, and that sound frequencies and rhythms play an important role in the driver responding appropriately. A team of Ford engineers spend their days dreaming up sounds and subjecting them to a battery of tests to determine which warnings help drivers best react to possible dangers and work in harmony with other sounds in the vehicle. This gruelling process involves complex scientific theory, listening clinics and on-road simulations to whittle down numerous sounds to the few that prove most effective.

In developing its safety sound cues, Ford relies on principles of music theory, mathematical analysis and psychoacoustics - the study of sound perception - to research properties such as pleasantness, loudness and sharpness. As a musical composer might select from different types of sound to cast a specific mood, Ford sound technicians choose from a palette of psychoacoustic parameters to create the ideal acoustical and vibrational environment.

The goal of the sounds is not to entertain you; but to help make sure you respond quickly to the driving environment that can change instantly. Ford's preliminary research shows certain types of alerts work better in certain situations, and that sound frequencies and rhythms play an important role. For instance, in studies designed to see how proactive safety features can best alert drivers to potential accidents, drivers responded faster to audible alerts that sound more authoritative and are emitted in a rapid, staccato rhythm. Drivers also indicated a preference for a combination of warnings - audio alerts backed up by a visual warning.

As a result, Ford pairs audible alerts with visual cues for scenarios requiring a more urgent driver response. Another important consideration is the presence of other sounds, including the radio or other in-car signals that compete for the driver's attention.

Ford uses a variety of methods to test the effectiveness of audio and visual components. To re-create the driving experience, Ford pumps wind and road noise into cars isolated in a soundproof chamber with mannequins equipped with precise microphones that capture high-fidelity recordings of the alerts as a driver would hear them. Many of the prevailing sounds incorporate a series of notes along the major scales, with intervals that are pleasing to the ear, yet discernible enough to break through the ambient background of the car and other sounds competing for the driver's attention.

Some sounds that do well in the consumer preference testing do not meet the standard for eliciting the proper driver response, such as the soft, electronic beat sound "Techno01", similar to club music around the world, which did well in the subjective studies but was not audible enough to cut through the car's background sounds.

Finding the right universal sound that works for all drivers is a challenging objective and one that transcends geographic boundaries. Because sensory perception and preference varies around the globe, Ford also tests some sounds in different regions to develop uniform cues that work in its various consumer markets.