By Amanda Djäknegren
One of the challenges during the electrification of trucks is that the surrounding Vulnerable Road Users still have to perceive and understand the truck’s motion and position relative to themselves despite the lack of sound of a large diesel engine. During the development of the Acoustic Vehicle Alerting System (AVAS), I designed, performed and analysed a user study to understand what components of the sound help the user distinguish a truck from a car, as well as makes it possible to identify idling, acceleration, constant speed, deceleration, and reversing.
The questionnaire
In preparation for the study, sounds from a diesel truck as well as a diesel car was recorded, and adjusted so that the sound level was equal in all audio clips. Since the user research was conducted digitally, the form asked the users to wear headphones, and adjust the volume so that everyone experienced the sounds as similarly as possible. The questionnaire was sent out to bicyclists, pedestrians, car drivers and truck drivers in order to understand if there was a difference in understanding the sounds between the groups.
Try it yourself!
Audio question 1
Listen to the audio clip, and then answer the questions below.
Is this the sound of a truck or a car?*
What type of sound is this?*
*Note that your response is NOT saved, this is only to illustrate what the survey looked like.
Click here to reveal the correct answers
This was a truck reversing, which was one of the most difficult for participants to distinguish. At the time of this survey, there was no legal requirement to have a special sound for reversing, but it was clear that most users had come to expect a beeping noise when trucks reverse.
The experience of the sound
After listening and guessing the sound, the users were also asked how they experienced the sound and were asked to rate from “very unpleasant” to “very pleasant”. While the goal wasn’t to create an entirely unpleasant or pleasant sound, the sound needs to guide the user of when to be alert or aware. Therefore, understanding which elements of the sound do this without being annoying was helpful to the continued development of the AVAS sounds. The participants were also asked if they thought it was difficult or easy to identify the sound, as well as what made it easy or difficult to identify. This gave further input in what cues were helpful to identify the sounds, but was also what cues can be confusing for the user.
How do you experience this sound?*
Imagine being in close vicinity to the vehicle. How do you feel when hearing this sound?
Very pleasant Very unpleasant
Was it easy or difficult for you to identify the sound?*
*Note that your response is NOT saved, this is only to illustrate what the survey looked like.
The data was then analyzed and presented in such a way that stakeholders could easily utilize the results in their continued work.
In total, the user were asked to identify 10 audio clips, six of which were from trucks, and four of which were of cars.
Another example can be found below.
Audio question 2
Listen to the audio clip, and then answer the questions below.
Is this the sound of a truck or a car?*
What type of sound is this?*
How do you experience this sound?*
Imagine being in close vicinity to the vehicle. How do you feel when hearing this sound?
Very pleasant Very unpleasant
Was it easy or difficult for you to identify the sound?*
*Note that your response is NOT saved, this is only to illustrate what the survey looked like.
Click here to reveal the correct answers
This was a car decelerating. This sound was often confused with a truck. While it’s easy in real life to distinguish between a truck and a car due to the loudness of the engine, when removing that aspect, this sound in particular became difficult to distinguish.
