In this course you will learn about audio signal processing methodologies that are specific for music and of use in real applications. We focus on the spectral processing techniques of relevance for the description and transformation of sounds, developing the basic theoretical and practical knowledge with which to analyze, synthesize, transform and describe audio signals in the context of music applications. The course is based on open software and content. The demonstrations and programming exercises are done using Python under Ubuntu, and the references and materials for the course come from open online repositories. We are also distributing with open licenses the software and materials developed for the course.
Introduction to Freesound
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来自 Universitat Pompeu Fabra of Barcelona 的课程
Audio Signal Processing for Music Applications
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从本节课中
Discrete Fourier transform
The Discrete Fourier Transform equation; complex exponentials; scalar product in the DFT; DFT of complex sinusoids; DFT of real sinusoids; and inverse-DFT. Demonstrations on how to analyze a sound using the DFT; introduction to Freesound.org. Generating sinusoids and implementing the DFT in Python.
与讲师见面
Xavier SerraFull Professor
Dept. of Information and Communication Technologies, UPF
Prof Julius O Smith, IIIProfessor of Music and (by courtesy) Electrical Engineering
CCRMA
Welcome back to the course on signal processing for music applications.
In this class, in this demo class, I want to introduce Freesound.
You already might have noticed that all the sounds I have been using, and
all the sounds we will be using come from this website from Freesound.
So, it's a great resource for this course, and I want you
to understand a little bit more and to take advantage of it as much as possible.
So, Freesound is a website that was started the music technology group.
Universitat Pompeu Fabra, Barcelona close to 10 years ago.
But the truth is that its been maintained and
supported by a large community of people that believe in it,
that love to play around with sounds and
they're contributing and maintaining this website.
So, let's go to the website, okay?
So, here is the website.
And it is a website that already has a huge number of sounds.
Currently has more than 20,000 sounds, and there's a lot of activity around it.
There is more than 50,000 people every day accessing,
downloading sounds, and contributing some way or another.
But anyway let's start using it.
So typically, what you do is in the search
menu you will type the name of some sound.
So, for example, let's type flute note, okay?
And this returns the sounds that it has found that include these two names,
either in the tags or in the descriptions.
It has found 1074 sounds.
So, let's go maybe to one of these sounds.
Okay, so these are the sound of flute note before, and we can play it.
[NOISE]
[MUSIC]
Okay, so typically all the sound entries include a description of the sound.
This one of pretty good, so it has a description of how the sound was recorded,
and what it is.
And then it has some of the key descriptions of the sound.
And also, it has tags that
this is a very useful way for the other people to find this sound.
Through different concepts that might be related to this sound.
And here it has all the technical information about the sound.
Okay.
Let's go to back to the sound
results that we found, and here we have many other sounds, for example,
even sounds that, of course, are not flute.
For example, this ocarina sound,
but in the description it mentioned that it's a flute like sound.
We'll play it.
[SOUND] Okay, the green has a flute-like sound, but one way to search for
sounds that is quite interesting is through similarity,
which in fact what this does is analyzes all the sounds of free sound.
It analyzes the spectrum of all the sounds, and it looks for
other sounds that might have spectrums similar to this one.
So, this ocarina sound has a spectrum similar to this one.
So for example, this is a one-second nose flute.
And [SOUND] and yes, it's a sound very similar to ocarina.
And if we play all these other sounds, the distance increases, so
they will be less and less similar, but they have a similarity with this sound.
So, that's pretty good.
So, let's go back to the main page.
And in here, also you can search for sounds and
information through many other ways.
If you go to the sounds page in here you can browse
through all the sounds according to the tags and the packs or
for example, an interesting browsing possibility is what is called the geotags.
So geotags are sounds
that have been sort of identified with a geotag.
So sounds that have been recorded in a particular location in the world,
and that people have identified the place where this was recorded.
So you can find, so if we you look in Barcelona, of course, there is a lot of
sounds from our city because we are very active there, so this is Barcelona.
There is 2,300 sounds coming from Barcelona,
but there are sounds from all over the world.
And you can navigate through this sounds this way so that's pretty good.
Of course, once you like one sound, you can download it.
So for example, in the case of the sounds of this course I label
all the sounds with a particular tag which was asp-course.
So, if we look for a sound that have the asp-course
label or tag, you will find them all here.
So in this case here, it has all the sounds that I
have been uploading for the course.
[SOUND] So, you can play it of course.
[SOUND] But if we want to download this sound, we can just simply click download.
You have to be logged in, which in my case, I am already logged in.
So I can just download it, and
it will save the file in the same format that the sound was uploaded.
So that's pretty good, but
what I want to do now is to do the opposite, to upload a sound.
I think it's very good for people to upload sounds in this class that
might be of relevance for the course, or you might have a sound and
maybe interesting to analyze or you might have a sound that you have transform,
and that you want to share with other people.
So, I encourage to upload sound and maybe put the same label,
asp-course so that all the people can find your sounds.
So, let's think of a sound that we might want to upload that it's not there.
For example, let's see if there are many sawtooth, synthesis sounds of a sawtooth.
Well, there's quite a few, but
I don't see the standard kind of a straight sawtooth of high quality.
Here, there is one which is very weird because it's eight bits.
So okay, so let's go to audacity and let's generate a tone using a sawtooth.
Okay. So let's select sawtooth with frequency
440 hertz and let's put an amplitude of 0.5.
Let's have five seconds [UNKNOWN}.
Okay, so this is it [NOISE].
Okay, to upload that, let's maybe, to make it nicer add the fading at the beginning.
Fade out at the end [SOUND] okay.
And that signal we can save the file, export it.
And in the directory, let's put sawtooth, and it's 440Hz.
Okay.
So let's.
Okay. Let's save it.
We have it.
Now from the Freesound website, we can just click the upload sounds button.
And here upload and we'll have the sawtooth for 1140 hertz.
So, that's okay.
It's already done, and now what is important is to describe the sound.
So, it has the option to describe the sound, and here we click describe,
and we can specify tags and description of the sound.
So for example, for
description we can say, okay,
this was a sawtooth-generated
waveform, for example,
of frequency 440Hz of
five seconds generated with audacity.
Okay?
Let's put that five seconds.
Okay, and then in terms of tags we might put of course the word sawtooth.
We can use 440 hertz,
440 A4, so that's pretty good, is electronic
sound is produced with the synthesis techniques, and
let's put synth also, it's quite a common word.
It's wave form, okay that should right, so that's pretty good.
And let's just, well, in the pack,
these are the packs I have, and maybe I have a synthesis pack.
So, maybe let's put it there.
And a license, there is three types of license I can use,
Creative Common0 that means public domain anything can do attribution,
that means people have to say that it comes from free sound or
restrict that it should be use commercially.
So normally, I'd like the attribution.
So, go to attribution, and I will submit it and that's it.
It has already been uploaded, and
now there will be a moderators that will check if this
sound was well describe, and it is not in fringing.
Any legal thing, I will take it from any other place,
and then it will come up in Freesound.
Okay. That's basically what I wanted to say so
let's go back to here and Okay.
So, we have talked about Freesound,
and a very important concept like want to emphasize, and
that you should be familiar with all these licensing issues.
Creative commons is a great set of licenses and for
sounds are very much appropriate.
And Freesound uses them very well.
Okay, and then we have use of audacity to generate the Sawtooth.
And we have referred to this pack
within Freesound where I keep all the sounds for the course.
And that's all, so I have introduced Freesound.
Hopefully, this has been of interest to you.
And I have encouraged you to take advantage of it,
to use it, get sounds from it.
But even more, to upload sounds to the things that you believe might
of interesting, may be interesting to the community.
And through this course, you will have the opportunity to generate and
record sounds that might be of relevance to Freesound.
So anyway, thank you very much, and I hope to see you all next class, bye-bye.
