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07_Noise - Open 07_NoiseA.pd If you press “START” you...

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Lab 7 - Digital Noise Just as Nyquist’s limit shows that the digital signal is discrete in time, the use of fixed-precision samples makes it discrete in level as well. Here are 5 pictures of Dr. Harry Nyquist, each one using fewer levels of gray: High Resolution Photo (8 bits per pixel) 16 gray levels (4 bits/pixel) 8 gray levels (3 bits/pixel) 4 gray levels (2 bits/pixel) 2 gray levels (1 bit/pixel)
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As detail is lost, artifical boundaries appear, and important features are lost, like his glasses in the last image. Remarkably, much information is preserved, such as the pattern of his necktie. In audio signals the loss of detail translates to an increase in digital noise. You need download three files: 07_NoiseA.pd, 07_NoiseB.pd and noisam.aiff Make sure all three files are placed in the same folder/directory on your computer.
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Unformatted text preview: Open 07_NoiseA.pd. If you press “START” you will hear a sine tone at 200 hz, with a resolution of 16 bits. Reduce the resolution. At what resolution do you first hear the sound change? Continue to reduce the resolution and describe what you hear, and what you see in the waveform window. Close 07_NoiseA.pd and open 07_NoiseB.pd. Press "start." You should hear a familiar song. Again, reduce the resolution until you hear noise appear. At what resolution is did you hear noise in the sound? Continue to reduce resolution and describe what you hear. Finally, reduce the resolution to 1 bit (turn the volume down a bit because the high frequencies are very intense) and listen to the song. Most of the information is lost, yet you can still make out some features of the song. Which features are preserved?...
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