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Vocal Coach

Vocal Coach. ECE 3551 – Microcomputer Systems 1 Fall 2010 Siobhan Ireland. Contents. Overview of Project Generating Musical Notes Filtering Audio Input Improvements Conclusion. Overview of project.

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Vocal Coach

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  1. Vocal Coach ECE 3551 – Microcomputer Systems 1 Fall 2010 Siobhan Ireland

  2. Contents • Overview of Project • Generating Musical Notes • Filtering Audio Input • Improvements • Conclusion

  3. Overview of project • The initial idea for my project was to use the BF533 EZ-Kit Lite board to create an electronic vocal coach • This project could have real world application in helping people train their vocal ability • I implemented the project by splitting it into two parts: generating musical notes, and filtering audio input

  4. Generating Musical Notes • I calculated note frequencies over a range of four octaves and from each octave chose one note – corresponding with the four push buttons • The frequencies were found using the equation:

  5. The algorithm for generating the notes is: • Which in code translated to: y = 7*x*sinf[w0*n] if(note==1) //note C3 { n %= 367; //nmax y=7*x*sinf(0.01712335 *n); y0=(int)(y); //send output to left and right audio channels iChannel0LeftOut=y0; iChannel0RightOut=y0; } • I had a few difficulties getting the code working • Once working I tested various values for amplitude

  6. The code for generating musical notes was successful • Push button PF8 = note C3 • Push button PF9 = note D4 • Push button PF10 = note F5 • Push button PF11 = note A6 • Demonstration

  7. Filtering Audio Input • The initial purpose for this section of the code was to accept user input in the form of singing and analyze which octave the frequency lies in • I chose first to test the code using input in the form of a song from my I-pod • The filter values were chosen based on the calculated octave frequency values

  8. The algorithm for IIR filters is: • The filters were created using MATLAB fdatool • IIR filters were chosen over FIR filters because they have less coefficients and produce clearer, crisper filtering

  9. The c code for the IIR filters is given below: voidlow_lowpass_filter(void) { inti = 0; //reset loop (row) counter //set input equal to iChannel0LeftIn shifted by 8 //iChannel0LeftIn>>8 shifts the original audio from 24 bits to 16 bits x_input = iChannel0LeftIn<<8; for(i=0; i<13; i++) //for row 0 to row 13 { //implementation of algorithm //calculate input from d[m] = x[m]-a2d[m-2]-a1d[m-1] D_low[i][0] = x_input - (low_lowpassA[i][2]*D_low[i][2]) - (low_lowpassA[i][1]*D_low[i][1]); //calculate output from y[m] = b2d[m-2]+b1d[m-1]+b0d[m] y = (low_lowpassB[i][0]*D_low[i][0]) + (low_lowpassB[i][1]*D_low[i][1]) + (low_lowpassB[i][2]*D_low[i][2]); x_input = y; //set x_input to previous value of y D_low[i][2] = D_low[i][1]; //shift values stored in array D_low[i][1] = D_low[i][0]; //shift values stored in array } //shift value of y (typecast as int) by 8 bits from 32 bits to 24 bits //send output to left and right output channels iChannel0LeftOut=(((int)y)>>8); iChannel0RightOut=(((int)y)>>8); }

  10. Initially I applied band-pass IIR filters with frequencies corresponding to the octaves. There was no audible change to the input • Next I applied band-pass IIR filters with large frequency ranges. There was still no audible change • I then switched to low and high-pass IIR filters with original frequency values. Still no change was heard • Lastly I applied low and high-pass IIR filters with large frequency ranges. They successfully altered the audio input

  11. There was no point at this stage of development to add a microphone, as the filters wouldn’t work as originally planned • No button, - LED 9 - original audio • PF8 pressed - LED 4 - low range filter • PF9 pressed - LED 5 -low-mid range filter • PF10 pressed - LED 6 - high-mid range filter • PF11 pressed - LED 7 - high range filter • Demonstration

  12. Improvements • Lab access • Equipment access • Improve filters • Add microphone • Design user feedback • Combine codes • Eventually extend number of notes played

  13. Conclusion • Overall I consider the project successful • The project utilized and built upon knowledge gained through lecture and lab • Generating musical notes was new to me and was implemented successfully • Filtering audio was adapted from lab work and while it works correctly, it needs further development to work as originally planned

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