Audio Position Tracker

I need to build a simple prototype to test a design theory. If the tests are successful, I will post a new project to design the software for the final machine. I need to experiment with a "time of flight" object location system. I need to locate a microphone in an empty room by sending a tone from speakers located in each corner of the room. Please reference my drawings attached to this project posting. The test prototype will consist of a LAPTOP COMPUTER, a USB HUB, five USB SOUND CARDS, four SPEAKERS and a MICROPHONE. Here is the theory of operations: The program will send a short tone burst through USB SOUND CARD #1 and SPEAKER #1. USB SOUND CARD #0 will be listening for the tone burst through a microphone. When the tone burst is heard, a "time-of-flight" calculation will be stored. Now USB SOUND CARD #2 will send a short tone burst through SPEAKER #2. USB SOUND CARD #0 will be listening for the tone through the microphone. When the tone is heard, a "time-of-flight" calculation will be stored. Now USB SOUND CARD #3 will send a short tone burst through SPEAKER #3. USB SOUND CARD #0 will be listening for the tone through the microphone. When the tone is heard, a "time-of-flight" calculation will be stored. And finally USB SOUND CARD #4 will send a short tone burst through SPEAKER #4. USB SOUND CARD #0 will be listening for the tone through the microphone. When the tone is heard, a "time-of-flight" calculation will be stored. The four stored "time-of-flight" calculations will be used by the program to assign "X-Y" coordinates for the location of the microphone (see my attached drawings). I need the program to display a red dot on the laptop screen at the "X-Y" location of the microphone. This sequence loops over and over to constantly update the microphone's location on the computer screen. If the microphone is moved, the red dot will travel across the computer screen to update the microphone's new location. For this design test I need to be able to change the following parameters: TONE GENERATOR FREQUENCY (in Hz) TONE LISTENING FREQUENCY (in Hz) SAMPLE RATE (the speed in which the loop of tone bursts and listening sequences run) "X" COORDINATE ADJUSTMENT (to fine tune the "X" location) "Y" COORDINATE ADJUSTMENT (to fine tune the "Y" location) The operating system will be WindowsXP and the USB SOUND CARDS will be the SYBA SD-AUD20066 (WindowsXP plug and play). More information on this USP Sound Card can be found here [login to view URL] I need to keep in a tight budget of less than $100 on this "test prototype" to see if it will work before spending more money on the larger finished product.