<< Chapter < Page Chapter >> Page >
In this section, we will go over the Matlab code we used to simulate our project, the various algorithms we tried, how we simulated "real-time", and how the matlab simulation dealt with real signals.

t 2 2 t 1 1 2 t 1 2 1 2 2 1 2 1 2 2
shows that the sum of two sinusoids that are out of phase is just another sinusoid with an amplitudedirectly related to the phase difference. Our goal is to adjust the phase difference by adding time delays to theincoming signals so as to maximize the amplitude of the output. The maximum occurs when the phase difference is zero,because the signals will add constructively. Once the maximum is found, the time delays used to achieve it tell us fromwhich direction the signals originated.

Since we are working with discrete-time signals, the time delays we tried were limited by the sampling frequency of theDSP boards, which is 48 kHz. By dividing the desired time delay by that sampling period and rounding to the nearestinteger, we converted our trial time delays into indices that could be used to select the correct sample out of the buffer.

So, the algorithm for delay-and-sum beamforming is straightforward, but there is room for a little bit ofcreativity in finding the amplitude of the summed sinusoids. We experimented with two methods to accomplish that task. Wewill call the first method "amplitude extraction," and the second "signal integration."

Amplitude extraction flow diagram

A flow diagram for the amplitude extraction method is shown in . We split the signal into two parts and multiply one part by t and the other by t . By low-pass filtering the results, we obtain the DC part of the signal which contains the amplitudeinformation. This algorithm has the obvious disadvantage that it is dependent on knowing the frequency of the incomingsignal so that the correct w is used in the multiplication step. In spite of that, we were originally selected it forimplementation on the DSP board because it showed extremely robust performance in the presence of loud noise. Addinggaussian white noise with a variance of 1 to a signal in the range -1 1 had no affect on the performance of the beamformer in our Matlab simulation. Unfortunently, the algorithm is tooslow to be used in real time. Evaluating two low-pass filters for every time delay combination tried was simply notpractical.

The signal integration method is much simpler computationally, which made it a better choice for our final implementation.We only had to square the beamformer output to make all the numbers positive, and sum the results over approximately onecycle of the incoming signal. The sum is similar to an integral over one period of the signal, except that thesamples aren't multiplied by the sampling period to make an "area." Our matlab simulation showed that the algorithm shouldwork, but that it is somewhat more sensitive to noise than amplitude extraction.

We were unable to try either of our Matlab simulations with real signals recorded from our microphone array because we had difficulty making stereo recordings. The computers we useddefaulted to recording from the microphone input (which is mono) instead of the line-in input, and we didn't haveadministrator access to change the settings.

Questions & Answers

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.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
Berger describes sociologists as concerned with
Mueller Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Audio localization. OpenStax CNX. Jun 06, 2011 Download for free at http://cnx.org/content/col10250/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Audio localization' conversation and receive update notifications?

Ask