EEN502Project•
on February 14th, 2010•
Part A
Click on one of the phonemes below to view it’s acoustic features.
Or click below to see 3D plots of Power Spectral Density vs Frequency vs Time.
For a downloadable zip file of the sounds, please click here. The differences between the major phonemic categories are seen in the above figures, and the results are as expected. Vowels exhibit highly periodic spectrograms, while unvoiced phonemes were largely characterized by their noisy spectrograms.
Part B
An ideal telephone channel was created using overlap and add frequency domain techniques with zero padding. The channel is shown below.
Both a spoken sentence and a sung sentence were passed through the ideal filter. The plots of their magnitude spectrums are below. If interested, check out the original song and the filtered song.
Also, the phonemes from before were run through this ideal filter. This had a particular effect on the voiced and unvoiced fricatives, since the filter removed aspects that previously distinguished the two.
Uncategorized•
on February 9th, 2010•
Our research group just bought a couple of these 40 mile range RF transmitters for our Everglades project. Doug Mann and I were tasked with getting them to talk to each other, and to our dismay, no tutorials existed on the interwebs. The documentation was little help because it kept on referring to the development board. Unfortunately, the dev board can’t be purchased separately, and we had already acquired two of these modules.
We tried a bunch of different ways to get them to talk serially to a computer, but let me just tell you what ended up working. After hours of frustration, I remembered something I read in the book Making Things Talk (great book, highly recommend) that explained a certain way to configure an XBee radio. This involved removing the ATMega chip from an Arduino Microcontroller which just turned it into a slightly more expensive – but easier to interface with – FTDI chip. An FTDI chip is used to interface with “old” communications protocols over USB. This chip is a part of every Arduino board, but can also be bought separately for a slightly more dedicated solution. I think this solution is pretty clever because Arduinos are ubiquitous these days.
Anyways, check out the final setup below. We have a breakout board for the transmitter, but we just wire wrapped it now for prototyping purposes. Aside – wire wrapping will change your life. You can see that the ATMega has been removed from the Arduino, and there are only 5 pins connected to 4 ports on the Arduino.
Check the data sheet because the pin numbering is a little weird, but we only connected the following:
Pin 1 – Ground
Pin 2 – 5 Volts
Pin 5 – Rx
Pin 6 – Tx
Pin 7 – 5 Volts
After doing this and plugging in the Arduino, we could send AT commands via any serial monitoring tool. Since you’re already using an Arduino, you can just use the serial monitor in the Arduino IDE, or use the “screen” command in Terminal for Mac OS X computers. Regardless, the X-CTU software is fantastic (albeit Windows only). I recommend finding a Windows machine to install X-CTU because it makes the process graphical and takes a lot of the guesswork out of it.
After configuring just two settings on the radios, we were sending data across the lake on campus at 115kbps! We’re going to do a longer range test soon.
This was a crucial step for us as far as the Everglades project is concerned. Check out our new $200 solar panel setup powering a Fit-PC:
Both a spoken sentence and a sung sentence were passed through the ideal filter. The plots of their magnitude spectrums are below. If interested, check out the original song and the filtered song.
Also, the phonemes from before were run through this ideal filter. This had a particular effect on the voiced and unvoiced fricatives, since the filter removed aspects that previously distinguished the two.
