# 0.3 Reconstructing a dft with a pitch shift

 Page 1 / 1
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.

how can chip be made from sand
is this allso about nanoscale material
Almas
are nano particles real
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
no can't
Lohitha
where is the latest information on a no technology how can I find it
William
currently
William
where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
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
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
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
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?
what is a peer
What is meant by 'nano scale'?
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 ?
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
Got questions? Join the online conversation and get instant answers!