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  • 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 ω from 0 to π ) in the same figure. Label the frequency axis in Hz, assuming a sampling frequency of 8 KHz. Remember that a radialfrequency of π 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] .

(1) Utterance of the word “zero”. (2) Wideband Spectrogram. (3) Narrowband Spectrogram.

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

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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
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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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