A FRAMEWORK FOR ACOUSTIC DEVICES POSITION CALIBRATION

This work proposes the development of an acoustic measurement calibration framework, in which the unknown position of the devices is estimated by an optimization problem using the acoustic information given by the room impulse response, taken and not taken into account the delay introduced by the devices in the processing chain.

In this document the user can find the documentation of the code implemented in this project.

Documentation of the code

The code of this project consists of series of functions implementing the calibration algorithm and a series of functions implementing a GUI for the easier use of the algorithm. Therefore, we can divide the documentation in three sections: Libraries used, Calibration algorithm functions and GUI functions

Libraries used

In order to implement this application the next libraries have been used in the code:

• matplotlib : Library for plotting results.
• numpy : Library to facilitate the management of the data.
• pandas : Library to facilitate the management of the data.
• scipy : Library to implement different functions like minimization, findpeaks, among others.
• tkinter : Library to design the GUI.
• openpyxl : Library that allows to load .xlsx files. PLEASE INSTALL THIS MODULE IF YOU DON'T HAVE IT

Calibration algorithm functions

These are the functions used to implement the theoretical part of the algorithm itself.

• find_directPath(this_rir, top_peaks = 15) : This function takes as input a signal (room impulse response in this project) and the number of peaks desired to search in and gives as an output the sample in which the first peak of the RIR, and therefore the direct path, is. It computes first the absolute value of this_rir because sometimes in the RIR the first peak (direct path) is negative.

• compute_distance(audio,fs,c,interp_factor = 2, do_interpolation = True) : This function takes as an input a room impulse response, the sample frequency, the sound velocity, the interpolation factor and the option of doing interpolation or not, and it gives as an output the distance in meters between the microphone and source correspondent to the RIR used as input. It basically compute the distance using the find_directPath function explained before and applying interpolation if the user wants it. From the find_directPath function it obtains the sample in which the first peak is and after that dividing by the sample frequency it obtains the time-of-arrival (TOA) and then it is multiply by the sound velocity to get the distance. The audio used as an input can be a matrix of (RIRlength x #KnownPositionDevices), giving back a vector of (1 x #KnownPositionDevices) with the distances between each device and the unknown device.

• calibration2D_nodel(audio,fs,PosKnown,c,bnds,nUnknown) : This function take as an input the data correspondent to the room impulse responses, the sample frequency, the known positions of the devices, the sound velocity, the bounds that contraints the search in the minimization problem and the number of the devices with unknown positions. It gives as an output the estimated positions (2-dimensions, (x,y)) for the devices with unknown position. Inside this function it can be found another function that it is the loss function to minimize (a theoretical explanation of this function is explained in the report of this project).

• calibration2D_del(audio,fs,PosKnown,c,bnds,nUnknown) : This functions does the same as the previous one but it estimates the possible delay introduced in the processing chain. As the one before this functions works for 2-dimensions.

• calibration3D_nodel(audio,fs,PosKnown,c,bnds,nUnknown) :This function works exactly the same as calibration2D_nodel but the output gives the estimated positions in 3-dimension (x,y,z).

• calibration2D_del(audio,fs,PosKnown,c,bnds,nUnknown) : This function works exactly the same as calibration2D_del but the output gives the estimated positions in 3-dimension (x,y,z).

GUI functions

These are the functions used to implement the GUI and its functionalities.

• load() : This function is the one that initializes all the needed variables and enable the rest of the buttons and inputs in of the GUI. It is called when the user presses the button Load in the GUI.

• open_file(i) : This functions is the one that allows the user to input the RIR's in the algorithm. As an input it takes the number of the device to which corresponds the RIR in order to keep the order of them. It also calls the next function load_rir. It is called when the button open next to # Device RIR in the GUI is pressed.

• load_rid(rir,n) : This function takes as an input the RIR and the number of device. It loads the main matrix data (initialized in load) with the RIR in the correspondent position according to the number of device. If you see the code of this function it can be seen that when it loads the RIR into the main matrix, it does it with a certain length (RIRlen); this is because the information required of the RIR is in these first samples and taking a bigger number of samples would increase the computation time.

• open_file2() : This functions does the same as open_file but it loads the matrix of the known positions. It is called when the user presses the button open next to Known Devices File.

• dimension() : This function is the one that manages the number of dimensions to take into account in the algorithm. It creates a checkbox Select 2D Room Bounds that if its checked eliminate the z coordinate.

• reset() : This function resets the GUI to the beginning to compute again the estimated positions

• set_bounds() : This functions loads the matrix bounds depending if we are in a 2D or 3D case. The bounds for this algorithm are the size of the room and a 0.5 to the delay.

• calculate() : This is the main function. It computes the estimated position of the devices using the rest of the calibration algorithm functions and taking into account the rest of variables like if the user wants to estimate the delay, or if the user wants 2 or 3 dimensions.

A better explanation and a better understanding can be obtained if the user checks the code and the comments all along the code.

GUI guide

To use the GUI it is recommended to follow the next steps:

• First, introduce the number of 'Known position devices' and 'Unknown position devices' (a number), and press the button Load

• After that the user will find an GUI like this:

• Now the user has to follow the numbers of the next image:

• 1.- Insert the excel (.xlsx) file with the known poisitions pressing the open button. (Remember to leave in blank the first row of the excel file.
• 2.- Insert the excel (.xlsx) file with the data corresponding to each unknown device. This should be a matrix of (2000 x NumberOfKnownPositions), the 2000 is the RIR length used, so please if your RIR is smaller than 2000 samples zero-pad it. At the end, the matrix should be compose of N columns and each column should contains a RIR.
• 3.- Insert the size of your room, selecting if you want the z-coordinate to be taken into account or not (3D or 2D). After that press the button Ok.
• 4.- Insert the sample frequency in numbers.
• 5.- Select if you want to estimate the delay or not.
• 6.- Press the button calculate and wait for the estimation and the plot.

If all the steps have been followed correctly the user should ends up with something like this:

After that the user can press the button reset and start again from the first step of this guide.