By Morgan Robinson

PIANO NOTE RECOGNITION

WHY I CHOSE THIS TOPIC• I was in band for 8 years of my life

• I play the piano

• Matlab is a strong program for signal processing

BASIC CONCEPT• Import wav file of simple piano song ex. Mary had a little lamb

• Separate the file into segments of data for each note

• Determine the frequency of each note

• Transform the frequency into one octave

• Compare that to the known frequency of notes

• Print the result

SOURCE CODE• function [ notes ] = project1( file )

• [y, Fs] = wavread(file);

•

• onsets = findonsets(y);

•

• F = frequency(onsets,y,Fs);

•

• F1 = correction1(F);

•

• notes = Note1(F1);

•

• end

IMPORT WAV FILE• Wavread

• [y,fs] = waveread(‘file’);

• y = sample data

• fs = the sample rate in Hertz used to encode the data in the file, basically the number of samples per second (fs = frames per second)

DETERMINING NOTE WINDOWS (ONSETS)• Tried a lot of different methods

• function [ onsets ] = findonsets ( y )

• L = length(y);

• S = 1; %status trying to find begining (on/true)

• k = 1; %position in array

• topthresh = .2*(max(y));

• bottomthresh = .05*(max(y));

• for P = 51:L-50

• if S == 1

• if max(abs(y(P-50:P+50))) > topthresh

• S = 0;

• onsets(k) = P;

• k=k+1;

• end

• else

• if max(abs(y(P-50:P+50))) < bottomthresh

• S = 1;

• onsets(k) = P;

• k=k+1;

• end

• end

• end

DETERMINING FREQUENCY

• function [ F ] = frequency( onsets,y,Fs)

• i = length(onsets)/2;

• a=1;

• b=2;

• for j=1:i

• z=y(onsets(a):onsets(b));

• L = length(z);

• fftz = fft(z)/L;

• power = 2*abs( fftz(1:round(L/2)));

• freq = ((1:L/2)*Fs/L);

• [C,I]= max(power);

• F(j) = freq(I);

• a=a+2;

• b=b+2;

• end

• end

FFT picks out individual frequencies in some signal and shows you how much of your total signal (in the time domain) is in a particular place in your frequency domain.

TRANSFORM THE FREQUENCY • function [ F1 ] = correction1( F )

• i=length(F);

• for j=1:i

• [F1(j)] = correction(F(j));

• end

• end

TRANSFORM THE FREQUENCY• function [ F1 ] = correction( F )

•

• if F >= 254.284 && F <= 508.5675

• F1=F;

• elseif F < 254.284

• [F1] = correction(2*F);

• elseif F > 508.5675

• [F1] = correction(F/2);

• end

• end

DETERMINE THE NOTES• function [ Note1 ] = Note1( F )

•

• i=length(F);

• for j=1:i

• Note1{j} = Note(F(j));

• end

• end

Cell array

DETERMINE THE NOTES• function [ Note ] = Note( F )• • if F >= 254.28 && F < 269.40• Note = 'C';• elseif F >= 269.40 && F < 285.42• Note = 'C#';• elseif F >= 285.42 && F < 302.40• Note = 'D';• elseif F >= 302.40 && F < 320.38• Note = 'D#';• elseif F >= 320.38 && F < 339.43• Note = 'E';• elseif F >= 339.43 && F < 359.61• Note = 'F';• elseif F >= 359.61 && F < 380.99• Note = 'F#';• elseif F >= 380.99 && F < 403.65• Note = 'G';• elseif F >= 403.65 && F < 427.65• Note = 'G#';• elseif F >= 427.65 && F < 453.08• Note = 'A';• elseif F >= 453.08 && F < 480.02• Note = 'A#';• elseif F >= 480.02 && F < 508.57• Note = 'B';• else• error('frequency outside of acceptable range')• end• end

Demo

OTHER USES• Print sheet music

Length of notes

Octave

• Voice verification

• Voice Identification

REFERENCES• www.phy.mtu.edu/~suits/notefreqs.html

• www.mathworks.com/matlabcentral/

• www.reddit.com/search?q=subreddit%3A+matlab