Sonar CE v1.19

Description:
The SonarCE application is a real sonar for Pocket PC devices.

It uses the internal Pocket PC sound system to detect echo from different obstructions. It is quite precise around 5-10 cm at distance of 10 m. The up distance is only limited by the output power of the device and the speaker. This program can be use in air or in water but in water you need external microphone and speaker closed in water proof case. The main window toolbar contains the most important functions: send one chirp, sonar loop and analyze window. More advanced functions are hidden under settings menu. Additionally program is equipped with testing functions which helps to tune the parameters crucial for the Sonar CE application.

Physical background

The short sound (chirp) is sent by the speaker in interesting direction. When the sound “finds” on its way any obstruction, then is reflected and comes back to the device microphone. The device is in recording mode (after sending a chirp) and records the incoming sound wave. The recorded wave is autocorrelated with the output signal (played sound chirp). If the recorded data have the same or similar course as played one then the autocorrelation function returns maximum. Unfortunately the recorded signal is deformatted by the sound line (amplifiers, speakers, microphone and digitalization) and thus is not really the same. Additionally the correlation function itself generates sinusoid like course (due to limited data set) thus the correlation data needs a post processing. The correlation function can be improved by played the sound with different frequencies within the played time (1). This make the autocorrelation function more sharp (larger frequency spectrum sharper peak in autocorrelation function). The post processing function takes absolute value from the correlation function and reduces the output data to fewer points (let say 230). Every point represents the maximum value from the window operating on correlation function. For example, if the correlation function has 2300 points and the data window is 10 points wide then the first point from post processing data represents the maximum value from the first 10 point (of the absolute values) of the correlation data. The absolute distance measured by any sonar depends on the time the chirp is played (longer time more sound energy is cumulated in the chirp), from sound amplitude and in small degree from chirp frequency (different absorption wave in different medium e.g. low freq. waves can travel longer).



Menu bar and tool bar

To access additional functions, click on the menu options. This allows you to change the way the Sonar CE works, or change its working mode.

List of options in tool bar:
• One chirp
• Sonar loop
• Pause of sonal loop
• Stop of sonar loop
• Clear the screen and the stored data
• Linear mode
• Angular mode

List of options in menu bar:
• File: open, save, exit
• Analyze: chirp, play recorded buffer, auto correlate, post processing, analyze window and ruler
• Settings: set out signal, set wave format, set offset, set scale, use recorded chirp and info
• Tests: check recording, check audio system, check correlation function and search offset
• Help: about and help(now it works)


Requirements:
* Pocket PC Windows Mobile 2002
* Pocket PC Windows Mobile 2003
* Pocket PC Windows Mobile 5.0

More information:
Sonar CE

Download
* PPC 2002
* PPC 2003
* PPC 5.0