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Explain our goal and approach towards the project.


Analyze an input speech sample and return the vowels that are present.


Vowels are highly periodic, so they have distinctive Fourier representations. That is, there are large values at a particular frequency, in this case the lower end of the spectrum. By using Fourier analysis on an input signal, we will be able to detect via matched filters the input vowel sound.

Initially, we decided to build a database of the five fundamental vowel sounds. We used the MATLAB program. A project member recorded a voice sample of each vowel several times, ran the samples through the auto-regressive filter, and then calculated the first two formant frequencies from the frequency response of the vowel. Each voice sample was recorded at 8 kHz, and 256-sample windows were input into the auto-regressive model. The purpose of the auto-regressive model on each window was to get the transfer function of the vocal tract and output the frequency response of each voice sample. After the database was built, the next step was to record several samples of words or phrases and input them into the filter. To filter out the consonants, our program checked the magnitude values of the frequency response of each window. Normally, consonants will have significantly lower magnitudes than vowel sounds, and our program utilized a threshold to filter out only consonants. Next, we used a type of match filter to determine which vowel sound the sample corresponded to. We did this by setting up a series of five flags in our program, one for each vowel. At first, when each window came through, all the flags were set to true. The program then began comparing the known formant frequencies of each vowel to the voice sample. If the sample did not pass a threshold of a known vowel formant frequency, then the flag of that vowel was set to false. If there were multiple flags set true when comparing the first formant frequency of the voice sample, then the program then moved on to compare the second formants. After each 256 window was processed, we used a smoother to eliminate anomalies (due to unclear pronunciation, noise in the sample, etc.) and then output each vowel. Our final code used to detect vowels.

Flowchart of Approach

Auto regressive model

In our project, the only data for the vocal tract that we have is the windowed sound chunk that was produced at a particular time. Assuming a standard impulse input, the autoregressive model will take this chunk and compute a model for the vocal tract at the particular moment the sound was uttered. The vocal tract can be modeled simply as a series of linked cylindrical tubes, with the formants appearing due to the transition between these different tubes. Since the autoregressive model for this model of the vocal tract produces an all-pole transfer function (because we only have the output), ideally we should notice peaks at all of the particular resonant frequencies. These peaks do appear, and they are our formants.

Hamming window

Our windowing method that we used was a hamming window; you can see a very similar window, the hanning window, in the images below. The hamming window looks roughly like one period of a sine wave, as opposed to a rectangular window. This tapering at the ends is needed because otherwise you get anomalous behavior in the frequency domain. A hamming or hanning window provides a truer representation of the frequency content of the signal.

The top waveform is a segment 1024 samples long taken from the beginning of the "Rice University" phrase. Computing figure 1involved creating frames, here demarked by the vertical lines, that were 256 samples long and finding the spectrum of each. If a rectangularwindow is applied (corresponding to extracting a frame from the signal), oscillations appear in the spectrum (middle of bottom row). Applying aHanning window gracefully tapers the signal toward frame edges, thereby yielding a more accurate computation of the signal's spectrum at thatmoment of time. (From Spectrograms )
In comparison with the original speech segment shown in the upper plot, the non-overlapped Hanning windowed version shown below itis very ragged. Clearly, spectral information extracted from the bottom plot could well miss important features present in the original. (From Spectrograms )

Final code - formants.m

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
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
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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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