Ken:The other day, the news was talking about sound of a hybrid car. The driving sound is quiet that pedestrians can’t hear the sound, putting them at danger.

Dad: I know that news as well. Actually, I recently experienced a hybrid car coming close to me but not realizing it. I thought it could be dangerous.

Ken:In the news, they mentioned about testing a warning sound system when a car is approaching a pedestrian.

Dad: Warning sound to alert the pedestrians of the car's presence is being evaluated. People apprehend their surrounding using their five senses. For objects that aren't in contact, vision and auditory information is depended on. But with visual information, you can only apprehend the area you see. When a moving object, like a car, is coming from behind, auditory information is necessary to confirm safety. If the sound when coming close is too small, like a hybrid car, it is a natural thought to try to make a noticeable sound.

Ken:But since there are not too many hybrid cars, it may be okay to have cars with that sound, but once there are many hybrid and electric cars, it may seem odd for it to make sounds. Usually, it is a good thing for a car to become quieter...

Dad:You may be correct on that. Probably technologies to secure safety while keeping the environment quiet will be developed.

Ken:The news also said that quiet cars are a problem to visually impaired people. The cars coming from the front will also be troublesome as those coming from behind for these people.

Dad: Yes. Have you heard of "universal design"?

Ken: "Universal design"? Is that something like "barrier-free"?

Dad: Yes. It may be used as the same meaning but the following explanation describes the difference. "Barrier-free" is when the problem subject is visible, such as getting rid of stairs for the people in wheel chairs. But what if the design is for a sidewalk and the target group is the visually impaired? Not having steps between the roadway and sidewalk may make them feel uneasy. Universal design is a development and planning, taking into consideration many different people of many kinds. [Reference 1]

Ken: Does that mean "universal design" is necessary for the "warning sound" of hybrids and electric cars?

Dad:Yes, to obtain safety for any kind of people is the greatest factor for cars.

Ken:So it seems more difficult to keep lowering the vehicle noise.

Dad:That is where you need to think hard. The warning sound shall not be an unpleasant noise. In household electrical appliances, a rice cooker makes a sound when the rice is cooked. Such sounds that inform the status is called a notification sound, but the notification sound cannot be any sound.

Ken:Notification sound? Are sounds heard in games considered notification sounds?

Dad:Sounds from games are mostly sound effects. But when you press the wrong button, it makes a short buzz to let you know you didn't push the right one. To design a notification sound, it is important to have people imagine what it wants to tell from its characteristics (pitch, duration, tone). And on top of that, all people must not hate that sound as well.

Ken: I see. When you pass through the gate of a station, it makes a short and high noise but when you can't, it makes a ding-dong type noise. Is it recently that they started designing the notification sounds?

Dad:The importance of sound design has been recognized in recent years. First, automated machines have filled the city and now mechanically-operated machines are replaced by electrically-operated ones; it is a little old, but just like how a steam locomotive became an electric locomotive, and the gasoline-engine cars became electric cars. A mechanical device makes a noise which is associated with its action, but the electrical device doesn't. That makes things difficult, and makes the sound design more important.