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


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

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit 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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