While working on prototypes, Google engineers tested sound signals that were played only inside the car. When the control system decided it was time to sound a signal, a sound was heard inside the vehicle, and company employees recorded this event in a log. Then specialists analyzed how correctly and timely the alarm was triggered.
In addition, Google created several variants of sound signals. For example, if the danger is not too great, the car emits two short signals. This mode is used when a neighboring car begins to gradually shift towards the prototype. If the situation requires immediate warning of another driver, the Google prototype emits a louder and longer signal.
Also, sound signals were added to the prototypes to warn pedestrians and cyclists about the approach of a Google car.
