# 0.13 Lab 9a - speech processing (part 1)  (Page 4/5)

 Page 4 / 5
• You should use a Hamming window of length $L$ to window $x$ .
• Your window should start at the index $m$ of the signal $x$ .
• Your DFTs should be of length $N$ .
• You may use Matlab's fft() function to compute the DFTs.

Now we will test your DFTwin() function. Download the file go.au , and load it into Matlab. Plot the signal and locate a voiced region. Use your function tocompute a 512-point DFT of a speech segment, with a window that covers six pitchperiods within the voiced region. Subplot your chosen segment and the DFT magnitude (for $\omega$ from 0 to $\pi$ ) in the same figure. Label the frequency axis in Hz, assuming a sampling frequency of 8 KHz. Remember that a radialfrequency of $\pi$ corresponds to half the sampling frequency.

Hand in the code for your DFTwin() function, and your plot. Describe the generalshape of the spectrum, and estimate the formant frequencies for the region of voiced speech.

## The spectrogram

Download the file signal.mat for the following section.

As previously stated, the short-time DTFT is a collection of DTFTs that differ by the position of the truncating window.This may be visualized as an image, called a spectrogram . A spectrogram showshow the spectral characteristics of the signal evolve with time. A spectrogram is created by placing the DTFTs vertically inan image, allocating a different column for each time segment. The convention is usually such that frequency increases from bottomto top, and time increases from left to right. The pixel value at each point in the image is proportional to themagnitude (or squared magnitude) of the spectrum at a certain frequency at some point in time.A spectrogram may also use a “pseudo-color” mapping, which uses a variety of colors to indicate the magnitude of the frequencycontent, as shown in [link] .

For quasi-periodic signals like speech, spectrograms are placed into two categories according to the length of the truncating window. Wideband spectrograms use a window with a length comparable to a single period. This yields high resolution in the time domain but low resolution inthe frequency domain. These are usually characterized by vertical striations, which correspond to high and low energy regions within asingle period of the waveform. In narrowband spectrograms, the window is made long enough to capture several periods of the waveform. Here,the resolution in time is sacrificed to give a higher resolution of the spectral content. Harmonics of the fundamental frequency of the signalare resolved, and can be seen as horizontal striations. Care should be taken to keep the window short enough, such that the signal properties stayrelatively constant within the window.

Often when computing spectrograms, not every possible window shift position is used from the stDTFT, as this would result in mostly redundant information.Successive windows usually start many samples apart, which can be specified in terms of the overlap between successive windows. Criteria in deciding the amount of overlap include the length of the window, the desired resolution in time, and the rate at which the signalcharacteristics are changing with time.

#### 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
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Source:  OpenStax, Purdue digital signal processing labs (ece 438). OpenStax CNX. Sep 14, 2009 Download for free at http://cnx.org/content/col10593/1.4
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