<< Chapter < Page
  Speech synthesis   Page 1 / 1
Chapter >> Page >
This is an overview of the technique used to recompse an audio signal from one half of the DFT as well as shifting the harmonics in the signal.

Reconstructing the first half of the dft

With the first harmonic in hand (if, of course, it exists) the program is ready to manipulate the signal chunk by building a new DFT from scratch but based upon the original. The pitch you hear is the position of the fundamental frequency – the first harmonic. So the new DFT must take the frequencies at and around the original first harmonic and copy them, without alteration, to a spot further down the spectrum. Further, in fact, by exactly the desired pitch shift. The frequency of the second harmonic needs to be twice as large as the first so that the new voice sounds like it came from a real person, so the second harmonic and its neighboring frequencies are shifted twice as far down the spectrum as the first group. This is repeated with every harmonic in a similar way until half of the new DFT is full.

Reconstructing the second half of the dft

To reduce computational complexity, there is no need to perform this same task starting at the end of the original DFT working our way towards the middle. We know that the resulting time-domain signal we produce must be comprised of real numbers since people are going to actually listen to it, so we can exploit the symmetry properties of the DFT. That is, the DFT of a real-valued signal follows rule that the real part of the samples in the first half is a mirror image of the real part of the samples in the second half. Similarly, the imaginary part of the samples in the second half is a flipped (negative) mirror image of the imaginary part of the samples in the second half. This line simple for loop constructs the entire second half of the new DFT without any further analysis or computation. Here is an example of the magnitude of the spectrum for a chunk of signal before and after pitch manipulation. Notice how the harmonics are not merely shifted over, but spread out as well.

Dft of signal sample

Discrete Fourier Transform showing the spectra for one 512 sample chunk of the speech signal before manipulation by the Pitch Synthesizer.
Discrete Fourier Transform of the original DFT spectra for one 512 sample chunk of the speech signal after manipulation by the Pitch Synthesizer.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Speech synthesis. OpenStax CNX. Dec 18, 2004 Download for free at http://cnx.org/content/col10253/1.7
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Speech synthesis' conversation and receive update notifications?

Ask