ChinPen

I am going to use this blog to update the things I encounter and learn during the last few months of my two projects on Acoustics. The main idea is behind this is to verbalize my thinking so that I get to distil my thoughts and at the same time save them for future reference..

This will definitely get pretty technical with maths, engineering, signal processing programming and other types of ideas. I appologize in advance if you get bored and if it doesn’t make sense (but please do comment, and I will try to explain).. One of the hopes of this blog is to be distil the concepts (through discussion) to allow anyone and everyone to understand what I am doing.

The two projects I am working on right now are,

1. Investigation of Ground Burried Resonators (GBR) as a method for reducing outdoor sound propagation.
2. Auralization of a City Bus Passage.

I will post more information about both the projects as we go along. Please feel free to comment and ask questions.

Thanks for following and the comments!

-Chinmay

I had been meaning to take up the ‘proverbial’ pen for many days, but today something struck me that really made me want to say this..

What’s the idea behind Education?? What should education be about??

Too many times I have seen students (at all levels of education) chase grades to achieve excellence. The ‘what if I fail’ thought drives people to extremes. Learning and understanding goes down the drain and, mugging and memorizing takes it’s place. And finally what do you get?? A piece of paper with nothing inside YOU to back it’s claim. So what have we gained??

Education is your time to be free.. to explore, to invent and to dream. Spend your free time dreaming, coming up with elaborate ideas to use things taught in school. Explore the fields that interest you, add in details through the various means (internet, libraries, people) available. Take the time to apply the concepts and ideas learnt in school in real life, and that will help to concretize your knowledge and understanding of the world. The aim is not to absorb everything you get, but to concretize and internalize some part of it.

Going even further, I think there’s a difference to be made between ‘knowledge’ and ‘understanding’.. With all the resources available to everyone these says thanks to the internet, just knowledge is not enough. Anyone can learn a programming language in a few days, or learn to use a software tool in a few hours. It doesn’t take a genius but just someone who knows how to search Stackoverflow and Youtube. But someone who truly understands the fundamentals of a programming language, software tool, design methodology, etc and then can work his/her way up to the actual usage and implementation can really deliver much more effective, creative, elegant work.

I don’t mean to say that everyone has to understand everything they use from the fundamentals (well, if you do, then you’re truly awesome and I bow to thee), but at least the concepts, tools, techniques which are critical and center of your fields of study and/or work should be something you should definitely have an understanding of at a deeper level.

The world of tomorrow doesn’t need more factor manufactured graduates who are able to solve complex mathematical problems or design the exact same piece of work as the next person, but still can’t explain where and how it can be used in real life. We need people who can solve real life problems, create useful and practical things with the tools and techniques picked up during education. A deep understanding can lead to a elegant and effective application.

So what of grades. Like TheWheat used to say in the old days, “Ignore them, grades don’t matter”..

I’ve been hearing this confusion for many days, and decided this needs to be addressed.

What’s this 3G/4G that we keep hearing about everywhere, what does that mean to me??

The main reason for the confusion is the completely illogical and confusing naming convention and ‘branding’ (it sounds almost dirty) used by all the telcos and manufacturers.

Let’s go back to the basics..

1G. When mobile telecommunication started off, it was analogue. All communication between the phone and the tower was just a analogue modulated signal of the speech. This is called 1G. The standards used during these times were, NMT · AMPS · ETACS etc.

2G. With the digital age, this communication also became digital. The voice was digitized and transmitted to the tower as a stream of ’1′s and ’0′s .The main advantages of the 2G systems were that they were encrypted (kinda) so you couldn’t listen to other people’s conversations by just catching their signals using an antenna. The digital systems were more efficient (allowed more people to talk at the same time), and they were extensible (we’ll come back to this). Some of the famous 2G standards are GSM, CDMA(IS-95), iDEN. GSM was a part of a standards group called 3GPP and CDMA was part of something called 3GPP2 (Yes, I know it’s not exactly this, but this makes it easier.)

Since they were digital, many of these standards also allowed other digital data to be sent over these mechanism. That’s how they started to send SMS over these networks. That was 2G.

2.5G. A ‘half-step’ towards the next generation wireless telecommunication standards was the more generalized data-network (not restricted to SMS, etc). This brought GPRS (on 3GPP side) and CDMA2000 1xRTT(on 3GPP2 side), which are both data standards for 2G based networks.

2.75G. The 3GPP side decide to improve the data standards on their side of the ground by introducing EDGE (Enhanced Data rates for GSM Evolution). This improved the data rates and speeds of the existing GPRS networks.

3G. This was the 3rd iteration of the mobile telecommunication standards. Now this is where it get’s messy. To have any standard qualify to be ’3G’, it had to pass some regulations set by the ITU (International Telecommunication Union). But that’s ofcourse not how the telco advertise it.

So both the groups evolved their standards to quality for the new requirements. the 3GPP side came up with UMTS(W-CDMA). The W-CDMA here refers to the technology used, nothing to do with the CDMA standard from 2G. And the 3GPP2 side came up with CDMA2000 1xEV-DO, widely known as EV-DO.

3.5G Ofcourse, we can’t stop at 3G, so there was enhancement to the standards. The 3GPP moved to HSPA(HSDPA and HSUPA), while 3GPP2 side went with EV-DO RevA. These were mainly just speed bumps. Confused?? The guys at commandN did a nice table for everything until 3.5G.

3.75G We can’t stop here either. Even more speed 3GPP – HSPA+ ; 3GPP2 – EV-DO RevB.

3.9G (pre-4G) Now this is where the fun starts, ITU has come up with requirements for 4G. However, the two main standards (WiMAX and LTE) gunning for this can’t make it as of their current versions. But since everyone wants them to be commercialized and available, they decided to release the current versions.

WiMAX is an IEEE standard. The current version IEEE 802.16e-2005 can’t be officially called 3G, but it’s just one step before the next version IEEE 802.16m which should be called 4G.

LTE (Long Term Evolution) is the 3GPP groups version of next generation standard. Once again it can’t perform to the requirements of ITU and hence it’s considered 3.9G. The next version LTE-Advanced should be called 4G.

So what does it mean to you??

1. Anyone selling you anything which is ’4G’ is fooling you.. None of the 4G standards are matured and surely none have been commercialized. But, many telcos are bringing out LTE and WiMAX 802.16e and touting it to be ’4G’. Or ’4G-ready’. It’s not true.

2. You will have to change hardware. Yes. None of these technologies are interoperable. Just like GSM/CDMA, the phones and modes supporting these standards will be completely different (might even have very different mechanisms of authentications, for eg, SIM card). And most of the devices you have now that can do 3.5G/3.75G won’t be able to support 3.9G, but the reverse might be possible.

3. Faster mobile telephony coming soon. Yup! This is a given, going forward we’ll surely be seeing more and more devices supporting these new standards. Be careful what you buy. While most will support the fastest networks available currently, you don’t want to be left behind when the next changes comes.

P.S. To learn more about these standards, wikipedia any of these names.

I had talked about this looong time ago. And finally, I got a chance to study and work on some ideas about Directional Loudpseakers..

This was a poster we made for a course at school.. (It was for educational purposes)

We were trying to animate a mode which we measured on a beam for one of the labs at school… Ofcourse, Matlab it was for all the data processing and animation. We used the ‘patch‘ command to generate a surface with many elements and then moved them individually as per the measurements.

Now of course Matlab let’s you save each plot as a bitmap and play them back as a movie, but then it’s stuck in Matlab.. So how do you render it to a ‘standard’ file? Well, there is mpgwrite. You can find it at Matlab Central which is a really cool community where you can get tonnes of Matlab help and pre-written scripts and libraries which help you do lots of things..

Now, that’s all cool, but mpgwrite uses a Matlab executable(.mex) to do all the heavy lifting in C. So that mean I had to compile it myself. Not a problem I thought.. With macports, I should have all the things I need.. So we ‘make‘.. But I had some errors.. Looking at the forum for mpgwrite, I saw this solution…

A few hints on how to compile would be nice. I see others have had the same problem, so I’ll share how I managed to compile it under Mac OS X 10.4.8 running on an Intel Mac Pro.

1) First, you must change file pbmplus.h, at line 101 change to

#include <malloc/malloc.h>

Remember to put the number sign (i.e. the hash key on your phone) before the include statement.

2) Locate where you mex compiler is. In my case it is /Applications/MATLAB73/bin/mex. The full path must be written in the Makefile, i.e. it says simply “mex” on line 8, however it must be the full path to the mex compiler (as written above).

3) Type make at the command line (not in MatLab) – of course you must be in the src/ directory to do this.

4) Enjoy your .mex*-file!

Hope this helps.

And Voila!! It compiled.. So I continued to export the matlab animation and made an mpeg out of it… Check it out..

For those who are interested.. This is a mixed mode with some part torsional and some part bending wave..