Record sound through the phone vibration motor

What happens when the vibration motor to connect a wire to the audio input




Two engineers from the University of Illinois at Urbana-Champaign (USA) have developed an original method of hidden audioproslushki with your smartphone. The inventors have demonstrated that for recording sound good fit phone vibration motor coil. Coils recorded vibrations at a frequency of 2 kHz. Scientists have developed a sound processing method (pdf), amplifies the signal at higher frequencies, so that the phone records not only simple vibration, but also human speech.

The method showed good results in most cases (80%) recorded speech can be understood by hearing, and some words are recognized, even without post-processing, ie the original low-frequency material

. Signal is taken from the vibrating motor coil. Due to external vibrations (e.g., sound vibrations) the magnet moves within the coil by changing the magnetic field around, so that through the action of an electromotive force occurs in the coil of the induction current.



As shown, in the audio signal flow makes it quite accurately record the vibration motor fluctuations.

Here are the spectrograms for sound "sa" and complete the word "entertainment", recorded by a microphone (left) and the vibration motor (right).



The recorded sound is then passed through a filter to enhance the high frequencies. The illustration shows the original signal (a), Heat Map calculation of flow of sound energy after the signal processing to the vibrating motor (b) and, for comparison, the same sound, recorded by a microphone with normal sensitivity ©.



Demonstration
Example 1 The word "Entertainment"

vibrating motor to signal processing: wav


Vibration motor signal after processing: wav


Microphone Signal: wav


Example 2 The word "Author"
vibrating motor to signal processing: wav
Vibration motor signal after processing: wav
Microphone Signal: wav

Example 3 Word "Black"
vibrating motor to signal processing: wav
Vibration motor signal after processing: wav
Microphone Signal: wav

Example 4: The word "Look"
vibrating motor to signal processing: wav
Vibration motor signal after processing: wav
Microphone Signal: wav

Try to guess the word on the rumor An unknown word 1
vibrating motor to signal processing: wav
Vibration motor signal after processing: wav
Microphone Signal: wav

Unknown Word 2
vibrating motor to signal processing: wav
Vibration motor signal after processing: wav
Microphone Signal: wav

Example 5 The word "Often"
vibrating motor to signal processing: wav


Vibration motor signal after processing: wav


Microphone Signal: wav


Scientific work is theoretical. In practice, this method is difficult to use, because you need to gain physical access to the phone and modify it.

But this is an important study for understanding how new ways of wiretapping theoretically become possible in the future. Paranoid may assume that such minor modifications will contribute to the phones that are certified for use on the market of a certain country, directly at the production stage or certification.

In any case, if you suddenly notice that your phone vibration motor wire connected to the audio input - it is an occasion guard

. By the way, earlier computer security conferences have examined seem to work, which theoretically allow you to record sound and speech recognition using:

phone gyroscope: Gyrophone, pdf, Conference USENIX Security Symposium 2014 < / phone's accelerometer: AccelWord, pdf, conference MobiSys 2015; physical object vibration: Ripple, pdf, NSDI Conference in 2015; more efficient appliances Ripple II, pdf, NSDI Conference in 2016.
Source: geektimes.ru/post/277020/