The participants in the user studies were equipped with acoustically transparent headphones. With the help of these, they could clearly hear both the music and sounds from the surroundings.
"Safety was also one of the aspects we investigated. Most participants thought that it was relatively easy to take the traffic and the environment into account while navigating with the help of music. They felt safe during the tests," Albrecht says.
In the study the direction where the music was heard from was modified using HRTFs (head-related transfer functions). These functions add a sense of direction to a sound presented with headphones, as the functions include subtle hints of the direction, such as level and time differences between the ears.
"It is important to know the compass direction of the head, that is to say, in what position the head is, so that the direction of the spatial sound is stable even if the head moves. In this study this was done with the help of a special head orientation tracker that the cyclists had attached to the helmets and the pedestrians to the headphones," Albrecht states.
This work by researcher Robert Albrecht and professor Tapio Lokki from the Aalto University Department of Computer Science, together with Riitta Väänänen from Nokia Technologies, is the continuation of a previous navigation study by Nokia, in which the direction of the sound of a walking horse was used as the navigation cue.
"The sound of the walking horse was chosen because it does not belong to a typical urban environment. Thus it can easily be distinguished from the surrounding acoustic environment. The user study participants said that it was easy to follow the sound of the horse in the background, while at the same time paying attention to the traffic or chatting with others. It is important that users can select the audio used for the navigation according to their mood, the situation and the environment," Väänänen underlines.
"Using sound for navigation leaves the user's hands and eyes free for other tasks. Spatial audio is a particularly intuitive method to guide people in different directions. These research results will hopefully contribute to the development of future navigation applications," Albrecht adds.
The reported study is the first to use exact presentation of the direction of music -- earlier studies have simply adjusted the balance of the music between the two ears to guide users.
