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Appendix for Audio Localization Project

Module by: Elizabeth Gregory, Joseph Cole

Summary: This section contains a few important links, the code that we used for the project, and the project executable files.

Matlab Code

  • new_sim2: 
    
function new_sim2(theta_true)
% Values, Vectors, and a Matrix
%theta_true = pi./2;
degree = 32;

c = 346.287;                    % speed of sound in air
N = 150;                        % length of the sample buffer
Fs = 48000;                     % sampling frequency
f = 500;                       % frequency of sine wave
M = 2;                          % number of microphones
dist = .1;
t = [0:N-1]./Fs;                % time axis
m = (M-1)./2;                   % array center
x = dist.*[-m:m];               % microphone location on the x axis
omega = 2*pi*f;                 % commonly used value

theta_test = [1:2:2*degree-1]*pi/(2*degree); % test vector of theta values
%theta_test = pi./2;
divisor = degree/8;             % region divisor
length_t = length(theta_test);   % length of the delay vector
A = zeros(1,length_t);           % initialize A vector

delay_true = x.*cos(theta_true)./c;  % actual delay
delay_test = x'*cos(theta_test)./c;  % test matrix of delay values
samples = round(2.*delay_test*Fs)./2;        % number of samples to shift in testing
index = samples - ones(M,1)*min(samples) + 1;


% Signal Simulation

for j = 1:M
    y(j,:) = sin(omega*(t-delay_true(j)));
end

% Region Approximation

for i = [1:length_t]
    for j = [1:M]
        y_delay(j,:) = y(j,[index(j,i)+50:index(j,i)+100]);    %delay y1 by the 1,i value using index
    end
    z = sum(y_delay);

    A(i) = sum(z.^2);
end

aa = find(A == max(A));
region = floor(aa(1)./divisor)
theta_range = [region-1 region]*pi/8;
if(0)
figure
plot(theta_test/pi,A)
end
  • sim_input3: 
    
function [region,theta_range] = sim_input3(theta_true,degree)

% Values, Vectors, and a Matrix

c = 346.287;                    % speed of sound in air
N = 150;                        % length of the sample buffer
Fs = 44100;                     % sampling frequency
f = 500;                       % frequency of sine wave
M = 2;                          % number of microphones
%dist = .32;                     % distance between microphones
dist = .5;
t = [0:N-1]./Fs;                % time axis
m = (M-1)./2;                   % array center
x = dist.*[-m:m];               % microphone location on the x axis
cutoff = 50;                    % cutoff frequency of filter
omega = 2*pi*f;                 % commonly used value
theta_test = [1:2:2*degree-1]*pi/(2*degree); % test vector of theta values
divisor = degree/8;             % region divisor
length_t = length(theta_test);   % length of the delay vector
A = zeros(1,length_t);           % initialize A vector
B = fir1(40,cutoff/Fs,'low');        % lowpass filter
delay_true = x.*cos(theta_true)./c;  % actual delay
delay_test = x'*cos(theta_test)./c;  % test matrix of delay values
samples = round(2.*delay_test*Fs)./2;        % number of samples to shift in testing
index = samples - ones(M,1)*min(samples) + 1;
cos_base = cos(omega*t(1:N));
sin_base = sin(omega*t(1:N));
SNR = 1000;
noise1 = randn(1,N)/SNR;
noise2 = randn(1,N)/SNR;

% Signal Simulation

y1 = sin(omega*(t-delay_true(1))) + noise1;
y2 = sin(omega*(t-delay_true(2))) + noise2;

% Region Approximation

for i = [1:length_t]
    y1_sample = y1(index(1,i):index(1,i)+40);    %delay y1 by the 1,i value using index
    y2_sample = y2(index(2,i):index(2,i)+40);
    z = y1_sample + y2_sample;
    z_cos = z.*cos_base(1:41);
    z_sin = z.*sin_base(1:41);
    
    z_cos_filter = sum(fliplr(z_cos).*B);
    z_sin_filter = sum(fliplr(z_sin).*B);
   
    A(i) = z_sin_filter^2 + z_cos_filter^2;
end

% figure
% plot(theta_test,A);
% title(theta_true)

aa = find(A == max(A));
region = floor(aa(1)./divisor);

if(0)
theta_range = [region-1 region]*pi/8;
figure
plot(theta_test/pi,A)
end

C Code

  • index.h: 
    
short index[2][32] = {
	{0x0001, 0x0001, 0x0001,0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0002,	0x0003,	0x0004,	0x0005,	0x0006,	0x0008,	0x0009,	0x000A,	0x000A,	0x000B,	0x000C,	0x000D,	0x000D,	0x000D,	0x000E,	0x000E},
	{0x000E, 0x000E, 0x000D,0x000D,	0x000D,	0x000C,	0x000B,	0x000A,	0x000A,	0x0009,	0x0008,	0x0006,	0x0005,	0x0004,	0x0003,	0x0002,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001,	0x0001}
};
  • loop_intr_pcm2.c: 
    

#include "index.h"

#define N 100			//sample buffer length
#define N2 128			//averaging buffer length
#define DEGREE 32		//number of theta test values to try
#define SUMSAMP 70		//number of theta test values to try

float Fs = 16000.0;		//irrelevant since jumper in 3-4

int* lights = (int*)0x90080000;

short buffer1[N] = {0};
short buffer2[N] = {0};
int buffer3[N2] = {0};
int buf_full = 0;
int buf_index = 0;

interrupt void c_int12()      //McBSP1 receive ISR
{
	
	int sample = input_leftright_sample();
   	
   buffer1[buf_index] = (short)(sample >> 16);
   buffer2[buf_index] = (short)sample;

	buf_index++;
	if(buf_index == N) {
		buf_index = 0;
		buf_full = 1;
	}
   	   	
	return;			//return from interrupt
}

void main()
{                           
	int i;  
	int j;   
	int k = 0;
	int z, test_amp;
	int region;
	int out;
	int sum = 0;
	
	int max_theta_index = 0;
	int max_amplitude = -1;
	
	for(k=0;k<N2;k++) buffer3[k] = 0;
	k = 0;

	comm_intr();            //init DSK, codec, McBSP
  	while(1) {
		if(buf_full) {
			buf_full = 0;
			max_amplitude = -1;
			
   			for(i=0; i<DEGREE; i++) {
				test_amp = 0;

				for(j=0; j<SUMSAMP; j++) {
   					z = buffer1[index[0][i]+j] + buffer2[index[1][i]+j];
					test_amp += (z * z) >> 15;
   				}
   			
   				if(test_amp > max_amplitude) {
   					max_amplitude = test_amp;
   					max_theta_index = i;
				}
   			}

   			region = max_theta_index >> 2;
   			sum -= buffer3[k];
   			buffer3[k++] = region;
   			sum += region;
   			
   			if(k == N2) {
   				k = 0;
   				out = sum >> 7;
   				/*if(out > 3)
   					out = 0;
   				else
   					out = 7;*/
   				*lights = out << 24;
   			}
   		}
	}
}
  • vectors_11.asm: 
    
*Vectors_11.asm Vector file for interrupt-driven program

    		.ref 		_c_int12    ;ISR used in C program
    		.ref     	_c_int00	;entry address
		.sect   	"vectors"	;section for vectors
RESET_RST:	mvkl	.S2	_c_int00,B0	;lower 16 bits --> B0
    		mvkh  .S2   _c_int00,B0 ;upper 16 bits --> B0
    		B	.S2	B0 		;branch to entry address
		NOP      			;NOPs for remainder of FP
		NOP				;to fill 0x20 Bytes
		NOP
		NOP
		NOP	
NMI_RST: 	.loop 8
		NOP    			;fill with 8 NOPs
		.endloop 
RESV1:	.loop 8
		NOP 				
		.endloop
RESV2:	.loop 8
		NOP				
		.endloop
INT4: 	.loop 8
		NOP  				
		.endloop
INT5: 	.loop 8
		NOP
		.endloop
INT6:  	.loop 8
		NOP
		.endloop
INT7:		.loop 8
		NOP
		.endloop
INT8: 	.loop 8
		NOP
		.endloop
INT9:		.loop 8
		NOP
		.endloop
INT10:	.loop 8
		NOP
		.endloop

INT11: 	.loop 8	
		NOP
		.endloop

INT12: 	b 	_c_int12		;branch to ISR
		.loop 7	
		NOP
		.endloop
		
INT13:	.loop 8
		NOP
		.endloop
INT14: 	.loop 8
		NOP
		.endloop
INT15: 	.loop 8
		NOP
		.endloop

Project Executable Files

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