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Two algorithms operating in the time domain to change the pitch of solo human voice.

Introduction

Time domain pitch shifting algorithms have several advantages over frequency domain approaches. First, the formants of the original signal can be preserved, meaning that the timbre of the input signal will be largely unaffected. Second, the computational complexity is much less for time domain algorithm because there is no need to take transforms of the data. Two different algorithms were created and utilized with the major difference being the way in which the section of signal that is to be overlapped and added is selected.

Through this overlap and add approach the signal retains most of its correct shape. For both algorithms the original signal was broken down into overlapping windows of a specified size and hop size (which should be consistent with the values provided to the detection algorithm). Then, for each window the detected period (one divided by the detected fundamental frequency) and target period is computed and used to build up the new data for that window. After the construction of each window, which is described further under the two approaches, the windows themselves where then overlapped and added to create the new pitch corrected output signal. When the detection algorithm decides that a given window is unvoiced (i.e. has no fundamental frequency), both algorithms just copy that window as is, without any modification. A Hanning window is used to filter out the inconsistencies created from adding together overlapping windows of the output signal. This helps in the smoothing process so that there are not large discontinuities between added segments.

Sample of human voice

Several periods of a human voice holding a note.

Psola : pitch-synchronous overlap-add

The key to PSOLA is the determination and utilization of pitch markers in the original signals. The idea is that these markers should be equally spaced throughout the signal (at intervals equal to the detected fundamental period), but also that they should be placed at a location for which the signal has a maximum value (a peak). These two constraints are often in conflict, especially since our assumption that the fundamental period is constant for the entire window is not entirely true. As a result, following the highest peak in the signal from period to period may require relaxing the requirement that the markers be exactly equally spaced. On the other hand, if we only follow the maximum peak without regard for the fundamental period, our markers no longer have any regard for the pitch of the window and are not useful.

In order to strike this compromise, we created a matrix where each column contains two periods of the signal and the center row starts at 0 and increments by one period each column. Then we used a dynamic path finding algorithm (created by Vladimir Goncharoff and Patrick Gries from the University of Chicago in Illinois) to find a path that went through the maximum peak as much as possible, but which did not exceed a given slope as it went through the matrix. Since a slope of 0 (horizontal line) means the markers are equally spaced, the slope is the factor that is adjusted to strike the compromise between following peaks and maintaining periodicity. Empirically, we found a suitable value of this slope to be around 4. In the diagram below these pitch marks are labeled as mi-1, mi and mi+1.

Pitch markers across windows

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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Ece 301 projects fall 2003. OpenStax CNX. Jan 22, 2004 Download for free at http://cnx.org/content/col10223/1.5
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