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Water Detection Library

Copyright 2014, Motim Technologies Ltd, All rights reserved. Licensed under the BSD 3-Clause License

Motim Technologies Ltd accepts no responsibility for damage caused to devices which are unsupported or not in a waterproof state.



This library was developed to allow waterproof Sony Xperia phones to detect when they are submerged in water to allow the creation of a range of novel apps.

Theory of Operation

The detector generates a test tone with a frequency beyond that of normal human hearing and records sound through the two microphones of the Xperia phone for processing. Spectrograms for both channels are generated and the minimum, maximum, mean and variance values for both spectrograms around the frequency of the test tone are calculated. These combined eight features (four for each channel), as well as an additional feature computed from the amplitude difference between the channels, are used as the inputs for a neural network with two outputs, the in air and in water states. The state with highest output value is considered to be the current one.

See "waterdetection.html" for more information.


To use the library for your own applications, import the WaterDetection project into an Eclipse workspace. In the project settings for your own application, add the WaterDetection project as a required project on the build path (under Java Build Path > Projects). Then make sure WaterDetection is ticked to be exported (Java Build Path > Order and Export). Finally, reference WaterDetection as an Android library on the Android page of the project settings.

The native components of the WaterDetection project need to be built before the detector will work. If you haven't already, install the Android NDK. Run ndk-build in the WaterDetection library folder, if the native compilation succeeds, there should be a range of folders for various architectures in the "lib" folder, each containing a file called

Finally, a few permissions need to be granted to your app in order for the water detector to set up audio playback and recording properly. In the AndroidManifest.xml file of your project, include the following lines:

<!-- Required for audio input to water detector -->
<uses-permission android:name="android.permission.RECORD_AUDIO"/>
<!-- Required for setting volume for measurement tone generator -->
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>

Demo Project

A Demo app demonstrating the Water Detection Library can be found in this repository called "WaterDetectionDemo". This demo app shows a phone and a bucket of water. When the physical phone is submerged the app shows the phone image as submerged in the bucket.

To use the demo project, import the WaterDetectionDemo project into the same workspace as the WaterDetection project and build/run it as an Android Application.