ALF - AudioLocationFinder

Audio Location Finder

Have you lost your friends in a crowd? Or do you want to estimate the width of an area outside?

Audio Location Finder displays the positions of you and your friends on a virtual map on your iPhone up to a precision of 50 cm. No GPS or Hotspot localization is needed! Only by the sounds around the distances and positions of the connected iPhones are calculated by this app.

Usage instructions:
  1. Connect two or more iPhones in the same WiFi network.
  2. Start the app on all devices.
  3. Clap some times at a small distance from the connected iPhones.
The distances and positions of all iPhones are displayed in the Localization view.
The TDOA view shows a list of connected iPhones and the distances to them.
Recorder lists detected audio events.

Technical background: The app records sound signals with the built-in microphone. The time points of the audio signals are exchanged to the other devices and the positions are calculated by the evaluation of the time differences of arrival (TDOA). This is also known as "multilateration". For deeper insight you might take a look into the Masterthesis and into the Technical Report.

Localization ViewLocalization view TDOA OverviewTDOA view Timestamp RecorderRecorder

AudioLocationFinder is a project of the Computer Networks and Telematics chair of the University of Freiburg.

(c) 2011 ConeHeads (
Johannes Wendeberg, Christian Schindelhauer, Thomas Janson)