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wodin
- Thread starter jesus 2
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prophet
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j2da2, can't sleep either?
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prophet
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jesus 2 said:
if you had as much work due this week as i do and if you were as good at procrastinating as i am, you wouldn't be sleeping right now either.
j2da2
well i'm just experiencing some insomnia...want to read me a bedtime story
prophet said:
sure...here goes:
For the first step, it was necessary to construct the computer-controlled actuation and data acquisition for acoustic plane waves setup as in figure 1. The setup uses Vscope, DSA, and ARB as the computer components: Vscope maps the voltage of electrical signals; the DSA, or digital spectrum analyzer, maps the power spectrums of electrical signals; and the ARB, or arbitrary waveform generator, acts as a function generator controlled by the computer and outputs electrical signals based on a defined function. The DAC is a digital to analog converter and outputs the signal produce by the ARB. The ADC is an analog to digital converter which reads in signals so be mapped by Vscope and DSA. The ARB signal is connected the speaker and cylindrical tube setup (which simulates plane wave) and to the ADC. The plane waves signals are picked up by the microphone attached to the meter stick, and then fed through an inverting op-amp and connected to the ADC.
With the computer-controlled actuation and data acquisition for acoustic plane waves setup complete, the ARB was started up and configured to output a 400Hz sine wave with a 2.0V amplitude, which produces a clearly audible signal. The ARB update rate was set at 50kHz and was not changed throughout the experiment. Vscope was then started and setup so that the driving signal (ARB) and the output signal (microphone) were displayed simultaneously. By moving the microphone over varying and arbitrary x (the distance measured from the open end of the cylindrical tube to the plane wave reception point), the maximum and minimum output voltages, E0max and E0min, were noted by visual detection on Vscope. Both signal traces were then saved for an arbitrary x approximately halfway down the tube. The DSA was then started up and configured to display the power spectrum of channel 1 in display 1 and the power spectrum of channel 2 in display 2. Both displays’ power spectra were saved. These steps were repeated so that a Vscope time trace and two power spectra were saved for a square wave of 200Hz and 0.5V and a triangle wave of 200Hz and 1.0V.
The ARB was then configured to drive a sine wave of 800Hz and 1V. In order to plot the wave phase, Ö, as a function of x, all phase differences of a multiple of ð/2 that occurred were recorded. This happens where the zero of one signal lines up with a zero or peak values of the other signal. The frequency of the sine wave was then reduced to 400Hz and the process of plotting the wave phase as a function of x was repeated.
Next, the wave speed of the driven signal was calculated. This was done three times. The first two were based on the determined wavelength for a phase difference of 2ð for the driven sine waves of 800Hz and 400Hz and equation B. The third value was determined using equation A.
that should put you to fuckin' sleep. buahahahahah.
j2da2
