query regarding linspace

the book code says

A = linspace(0, 0.9, (length(y)*0.2)); %rise 20% of signal
D = linspace(0.9, 0.8,(length(y)*0.05)); %drop of 5% of signal
S = linspace(0.8, 0.8,(length(y)*0.4)); %delay of 40% of signal
R = linspace(0.8, 0,(length(y)*0.35)); %drop of 35% of signal

y is a tone signal of music

if i change the first two values of linspace, there is no change in audio. what is purpose of linspace in this command

[Walter Roberson]

You need to be careful: linspace() always includes the first and last values in the range, so if you put D right after A, you would have two 0.9 beside each other. Sometimes that is what you want, but usually it is not.

Answer 1

[Wayne King]

Without more context, it's hard to say how they are using these vectors, but linspace() is just creating a linearly-spaced vector from A to B using the specified number of points. The spacing between points obviously depends on the starting and stopping points and the total number of samples (elements).

A = linspace(0,0.9,(length(y)*0.2));

Says "create a vector of linearly-spaced increments from 0 to 0.9 that is 20% of the length of y."

D = linspace(0.9, 0.8,(length(y)*0.05));

Create a vector that goes down from 0.9 to 0.8 using the number of points equal to 5% of the length of y.

    S = linspace(0.8, 0.8,(length(y)*0.4));

The above is just a vector of the same value, 0.8, that is 40% of the length of y -- [0.8 0.8 0.8 .... ]

Answer 2

[Wayne King]

You'll have to convert the cell arrays with cell2mat(), or you'll have to do something like this.

C = cell(2,1);
C{1} = randn(1e3,1);
tone = C{1}.*ones(1e3,1);

I personally recommend that you write your own little ASDR function that accepts a vector input, so you convert from a cell array to a vector outside the function or feed the function C{i} and then inside the function create your envelope and multiply your signal by it and then return your signal as the output.

[moonman]

Thanks King u really gave very good idea, i should do all this in function

i will try this and let u know

Answer 3

[moonman]

This is complete code, now kindly comment

fs=8500;
y=sin(2*pi*300*(0:0.000117:3));
A = linspace(0, .9, (length(y)*0.25)); %rise 20% of signal
D = linspace(.9, 0.7,(length(y)*0.05)); %drop of 5% of signal
S = linspace(0.7, 0.7,(length(y)*0.40)); %delay of 40% of signal
R = linspace(0.7, 0,(length(y)*0.30)); %drop of 35% of signal

ADSR = [A D S R] ;
x = zeros(size(y));
x(1:length(ADSR)) = ADSR;
tone=y.* x;

Actually ADSR is an envolop which give realistic audio to pure sinewave in audio signals

My question is this how ADSR in this code is knowing that initial part of signal y will get multiplied with .25 and it will gradually rise, then decay and so on

although the audio is Ok bbut i am unable to unuderstand code

Kindly see the pic of ADSR here http://gadgetgangster.com/tutorials/390

thanks for sparing time for me

Answer 4

[Wayne King]

They have created this envelope with

   fs=8500; 
   y=sin(2*pi*300*(0:0.000117:3)); 
   A = linspace(0, .9, (length(y)*0.25)); %rise 20% of signal 
   D = linspace(.9, 0.7,(length(y)*0.05)); %drop of 5% of signal 
   S = linspace(0.7, 0.7,(length(y)*0.40)); %delay of 40% of signal 
   R = linspace(0.7, 0,(length(y)*0.30)); %drop of 35% of signal
   ADSR = [A D S R] ;

Then they multiply the sine wave element by elementy by ADSR. The sine wave oscillates between [-1 1], but when you multiply it element by element by the ADSR envelope, the sine wave oscillates between positive and negative values within the shape of the envelope.

Answer 5

[moonman]

Ok thanks now i need one last favour. for one key this is working fine. now i want to implement ADSR on 8 keys. I tried it but having error. Without ADSR, my 8 keys are giving perfect tone but when i try to implement ADSR on 8 keys i get error

plz help me. code is written below

keys=   [40 42 44 45 47 49 51 52];
%notes   C  D  E  F  G  A  B  C
dur=0.25*ones(1,length(keys));
fs=8500;   %sampling frequency (it is explaied in part b)

C = cell(1, length(keys));
A= cell(1, length(keys));
D= cell(1, length(keys));
S= cell(1, length(keys));
R= cell(1, length(keys));% It will creat a cell array having one row and
% columns equal to number of keys
for i = 1:length(keys)   % The for loop continues till number of Keys
   C{i} = note(keys(i), dur(i)); % Function note is called which calculates
  %tone for each key for the specified duration. This tone is stored in 
  % C{i}
A{i} = linspace(0, .9, (length(C{i})*0.25)); %rise 20% of signal
D{i} = linspace(.9, 0.7,(length(C{i})*0.05)); %drop of 5% of signal
S{i} = linspace(0.7, 0.7,(length(C{i})*0.40)); %delay of 40% of signal
R{i} = linspace(0.7, 0,(length(C{i})*0.30)); %drop of 35% of signal
end

ADSR = [A D S R] ;

x = zeros(size(C));
x(1:length(ADSR)) = ADSR;
tone=C.* x;

The error is

??? Undefined function or method 'times' for input arguments of type 'cell'.

Error in ==> attempt22 at 31 tone=C.* x;

[Fangjun Jiang]

mis-match, C is cell array, x is double array

Answer 6

[moonman]

Wayne King u r great my problem is solved

Answer 7

[moonman]

I would like to declare Wayne King as guru of this forum. He saved me from mess by giving an idea and my task of several hours completed in few minutes

[Wayne King]

I'm glad you solved your problem and you're very (too) kind. There are many here who know far,far more than me and freely give so much of their time helping people. That's what makes the MATLAB user community so great. I'm amazed at the level of knowledge here, on the newsgroup, and the file exchange. And how generously they impart that knowledge to others.