Add Ford to the ranks of automakers adding sounds to notify pedestrians of oncoming electrified cars. The 2020 Escape Hybrid and Explorer Hybrid will both include a custom sound, O-29 (listen to it below) that plays when they're moving at speeds up to 19MPH. We wouldn't quite call it "melodious" like Ford does, but it's designed to be at once identifiable as a car sound yet gentle on the ears. The humming both modulates and changes frequencies to match speed, giving you enough cues to react without completely eliminating the usual hybrid quietness.