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Learn about simple functions and representing signals and use them to create your own groove.

Introduction

In this lab, you will learn about MATLAB function files, which we will refer to as m-files and have the file extension *.m , the same as script files. You will create a number of functions for manipulating sound signals to create a groove (a short song).

The difference between a function and a script is that functions can return values and take parameters, while scripts are simply a collection of commands. Unlike script files, any variables created in the function are not available after the function has run, that is, the variables are active inside the scope of the function, and the variables cannot be accessed out-of-scope. The MATLAB on-line help system has a nice write-up about functions and how to handle various things like returning more than one value, checking the number of arguments, etc. To learn more, type the following commands and read the online help:

>>help function>>help script

You need to use a text editor to create function files. MATLAB has an internal editor that you can start by clicking "File" and then "New" "m-file". You can also use other editors such as Notepad on the PC's, and pico , emacs , or vi on Unix machines.

Remember that in order to run custom scripts or functions, the MATLAB working directory needs to be set to the location of those files.

Sound in matlab

Download the sound samples from the sound resources page and save them to your working directory. Use wavread to load .wav files, and use load to load .mat files. Plot each one in turn, and try to guess what it will sound like (the name might help).

On a computer, sounds are represented digitally, which means that only samples of the signal at fixed time intervals are stored. We'll learn more about this later. For now you just need to know that the time interval Ts (or equivalently the sampling rate Fs=1/Ts) is something you need to keep track of for playing sounds.

Now play each sound. The goal is to learn how the time domain signal sounds. Use the sound command to play a sound signal. You must specify the playback sample rate (Fs), which will be the same as the sample rate of the sound samples on the web site (they are 8000 Hz). For example, if you wanted to play a sound called bell and its sample rate was 8000 Hz, then you would enter the following command, >>Fs=8000;>>sound(bell, Fs); If you use a different value for Fs, you will effectively be doing time scaling.

When working with sound in MATLAB, it is important to remember that the values of the audio signals are in the range [-1, 1].Keep this in mind when you are writing your functions. Your functions should expect inputs with values in the range [-1, 1] and anything out of that range will be clipped when you play the sound.

Function files

Before we can create our groove, we need to make functions that will allow us to modify the sound signals in various ways. After all, wouldn't it be boring to make a groove out of the same note over and over again? Let's create some functions that will let us time scale, reverse, delay, fade, and repeat a sound, and mix two sounds together.

Questions & Answers

show that the set of all natural number form semi group under the composition of addition
Nikhil Reply
explain and give four Example hyperbolic function
Lukman Reply
_3_2_1
felecia
⅗ ⅔½
felecia
_½+⅔-¾
felecia
The denominator of a certain fraction is 9 more than the numerator. If 6 is added to both terms of the fraction, the value of the fraction becomes 2/3. Find the original fraction. 2. The sum of the least and greatest of 3 consecutive integers is 60. What are the valu
SABAL Reply
1. x + 6 2 -------------- = _ x + 9 + 6 3 x + 6 3 ----------- x -- (cross multiply) x + 15 2 3(x + 6) = 2(x + 15) 3x + 18 = 2x + 30 (-2x from both) x + 18 = 30 (-18 from both) x = 12 Test: 12 + 6 18 2 -------------- = --- = --- 12 + 9 + 6 27 3
Pawel
2. (x) + (x + 2) = 60 2x + 2 = 60 2x = 58 x = 29 29, 30, & 31
Pawel
ok
Ifeanyi
on number 2 question How did you got 2x +2
Ifeanyi
combine like terms. x + x + 2 is same as 2x + 2
Pawel
x*x=2
felecia
2+2x=
felecia
Mark and Don are planning to sell each of their marble collections at a garage sale. If Don has 1 more than 3 times the number of marbles Mark has, how many does each boy have to sell if the total number of marbles is 113?
mariel Reply
Mark = x,. Don = 3x + 1 x + 3x + 1 = 113 4x = 112, x = 28 Mark = 28, Don = 85, 28 + 85 = 113
Pawel
how do I set up the problem?
Harshika Reply
what is a solution set?
Harshika
find the subring of gaussian integers?
Rofiqul
hello, I am happy to help!
Shirley Reply
please can go further on polynomials quadratic
Abdullahi
hi mam
Mark
I need quadratic equation link to Alpa Beta
Abdullahi Reply
find the value of 2x=32
Felix Reply
divide by 2 on each side of the equal sign to solve for x
corri
X=16
Michael
Want to review on complex number 1.What are complex number 2.How to solve complex number problems.
Beyan
yes i wantt to review
Mark
use the y -intercept and slope to sketch the graph of the equation y=6x
Only Reply
how do we prove the quadratic formular
Seidu Reply
please help me prove quadratic formula
Darius
hello, if you have a question about Algebra 2. I may be able to help. I am an Algebra 2 Teacher
Shirley Reply
thank you help me with how to prove the quadratic equation
Seidu
may God blessed u for that. Please I want u to help me in sets.
Opoku
what is math number
Tric Reply
4
Trista
x-2y+3z=-3 2x-y+z=7 -x+3y-z=6
Sidiki Reply
can you teacch how to solve that🙏
Mark
Solve for the first variable in one of the equations, then substitute the result into the other equation. Point For: (6111,4111,−411)(6111,4111,-411) Equation Form: x=6111,y=4111,z=−411x=6111,y=4111,z=-411
Brenna
(61/11,41/11,−4/11)
Brenna
x=61/11 y=41/11 z=−4/11 x=61/11 y=41/11 z=-4/11
Brenna
Need help solving this problem (2/7)^-2
Simone Reply
x+2y-z=7
Sidiki
what is the coefficient of -4×
Mehri Reply
-1
Shedrak
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
Kimberly Reply
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
Leonardo Reply
How do i figure this problem out.
how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
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Source:  OpenStax, Continuous time linear systems laboratory (ee 235). OpenStax CNX. Sep 28, 2007 Download for free at http://cnx.org/content/col10374/1.8
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