Audio Engineering Society
Convention e-Brief Presented at the 136th Convention 2014 April 26–29 Berlin, Germany This Engineering Brief was selected on the basis of a submitted synopsis. The author is solely responsible for its presentation, and the AES takes no responsibility for the contents. All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Audio Engineering Society.
Spatial Sound for Mobile Navigation System Wataru Sanuki, Julián Villegas, and Michael Cohen University of Aizu; Aizu-Wakamatsu, Fukushima 965-8580; Japan
[email protected], {julian, mcohen}@u-aizu.ac.jp
ABSTRACT We have developed a mobile navigation system, crafted using Unity and Xcode for iOS, featuring binaural spatial sound delivered via headphones. “Machi-beacon” is intended to promote traffic and pedestrian safety: a user selects a destination relative to her current position, and the application renders both a visual map and an auditory earcon at the goal. The apparent location of this earcon is adjusted to reflect changes in orientation of the user, modulating interaural level difference. To disambiguate front directions, the earcon switches between contrasting cues (differing in melody, rhythm, and timbre) that respectively confirm or contradict current heading. By desaturating the visual modality, smartphone users can focus on their environment and its hazards and rewards.
1.
INTRODUCTION
1.1 Background Texting while walking is potentially dangerous. The best way to solve this problem would be to avoid using distractive mobile devices when walking, but sometimes we require mobile device’s display. To ameliorate this problem, we propose to use spatial sound in combination with traditional navigation systems. Previous research explored similar goals, but in this project, the challenge was to construct it with the already integrated sensors of smartphone, hence increasing its portability and universality.
Figure 1 Warning against texting while walking
Sanuki et al,
Spatial Sound for Mobile Navigation System
1.2 Unity Unity [1] is a development framework that provides rich out-of-box functionality to create games and other 3D content. It can publish to various platforms, such as Mac, PC and Linux computers, Windows Store, the Web, iOS, Android OS, …
Distance cues: If range between audio listener object and sound object is short, the sound intensity becomes louder. Azimuth cues: When the sound object I at left of listener object, the intensity of left channel becomes louder. Effecting, azimuth cues are given by this interaural level difference (ILD);
1.3 Google Static Maps API The Google Static Maps API [2] lets programmers embed a Google Maps image on a web page without requiring JavaScript or dynamic page loading. The Google Static Map service creates a map based on URL parameters sent through a standard CGI HTTP request, returning the map as an image that can be displayed on a web page. It can assign center position by latitude and longitude and find a path between two points. 1.4 Spatial Sound Spatial sound is a technique to artificially reproduce natural three-dimensional acoustic imagery that many species (including humans) have mainly due to the presence of two ears, enabling binaural hearing.
We created a simple spatial sound application with Unity. First, we constructed a sound and audio listener objects. Next, we programmed the sound object behavior. In the prototype, the sound attitude and location of the mobile device are used to determine the relative orientation of the user with respect to the destination. The application renders spatial sound dynamically and runs in many environments including iOS and Android OS. 2.2 Create simple navigation system The simple navigation system was created with Google Static Maps API and Unity. The application has the following function.
1.5 Global Positioning System The Global Positioning System (GPS) [3] is a satellitebased navigation system made up of a network of satellites. It was designed to assist soldiers and military vehicles, planes, and ships in accurately determining their locations world-wide. However, in the 1980s, the U.S government made the system available for civilian use; Which applications are continuously evolving and expanding. Today, uses of GPS have extended to include both the commercial and scientific worlds. GPS is used in navigation systems and positioning tools in vehicles and outdoor activities. 2.
Movement cues: When a sound object is approaches of recedes from a listener object, the frequency of the sound modulates, as the well known Doppler effect.
METHOD
2.1 Spatial sound development Unity can create spatial sound by modeling a virtual sound objects (sources) and audio listener objects (sinks). Sound objects use media objects that can play sounds in virtual world. Audio listeners act as microphone-like devices: they receive input from audio sources. Spatial sound created by Unity has following attributes:
Get a present position data and orientation. Create a map image show to display. Rotate map image according to the user’s relative orientation to the target. Unity can get current data from a mobile device. This data comprise longitude, latitude, and bearing (course). The simple navigation application create map image using this data. For creating map image, it needs a center position, goal position, image size, and zoom data. The application sends an HTTP request to the Google Static Maps API to get a map image. After getting the image, the application create a plane object and paste the map image as the plane’s texture. The same information is used operating the spatialization illusion. Spatial sound made with Unity easy the distinction between to distinguish right and left. But, it is not easy to distinguish front and back. To solve this problem, I add a change kind of sound with orientation.
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Figure 4: Data flow 3.
Figure 2: Machi-beacon cartographic interface
CONCLUSION
In this research, we corrected navigation application that uses spatial sound and works in mobile devices. The application makes spatial sound dynamically and the sound gives the use cues about where the goal is. This application was submitted to the Aizu IT Forum contest [9] where it won an Encouragement Prize. In the future, when in-door localization matures enough, a similar technique could be used for in-door way-finding. 4.
REFERENCES
[1] “Unity-Game Engine,” http://unity3d.com/unity [2] “Static Maps API V2 Developer Guide,” http://developers.google.com/maps/documentation/ staticmaps/ [3] Jacquelyne Lan Ta, “Global Positioning System,” http://repository.library.csuci.edu/handle/10139/360 2 [4] “Geospatial Information Authority of Japan,” http://vldb.gsi.go.jp/sokuchi/ [5] “Kashmir 3D” http://www.kashmir3d.com Figure 3: Sound changing with orientation
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[6] “iOS Dev Center Apple Developer,” http://developer.apple.com/devcenter/ios/index.acti on [7] “Unity Scripting Reference,” https://docs.unity3d.com/Documentation/ScriptRef erence/ [8] J. Villegas and M. Cohen. “Gabriel”: Geo-Aware Broadcasting for In-vehicle Entertainment and Larger Safety. In Proc. 135 Audio Eng. Soc. Int. Conv., Tokyo, October 2010. '' [9] “Technology Made in Aizu” http://www.city.aizuwakamatsu.fukushima.jp/docs/ 2014010600059
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