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EngE_1104_Spring_2007_Lab_8_Students_Copy_V1A_TW -...

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Explorations Of Our Digital Future Spring 2007 Lab 8: Musical Note Recognition/Identification Copyrighted by: Jeremy Garrett and Tom Walker, Feb. 2006 – Jan. 2007 Warm-up: Complete the entire “Lab 2 Warm-Up Worksheet" before beginning the lab. Download (from the Blackboard website): "Sythn_Music_Box_Note_1.wav" and "Sythn_Music_Box_Note_2.wav" "Synth_Flute_Note_1.wav" and "Synth_Piano_Note_2.wav" and "AmpSpec.m" Read this entire document before beginning the lab. Verify that your notebook computer has a built-in microphone, or borrow (or purchase) one if it does not have one. Objectives: 1. To learn about musical notes and the mathematics behind them. 2. To gain an understanding of how sounds related to their associated (mathematical) graphs. 3. To learn how the complexity of the human voice compares with that of a musical instrument. Overview: In this lab, you will be given several sound files that have been stored as uncompressed MS Windows "wave files." You will then find the frequency content of the sound files and identify their fundamental frequencies (the lowest frequency – that will also have the largest amplitude), using the AmpSpec function (which you were asked to download). Because each musical note has a distinctive fundamental frequency, you can use the functions provided to determine which note is associated with each sound file. You will notice that there are more frequencies than just the fundamental frequency on each of the graphs. The extra frequencies can be a result of neighboring string vibration or simply the note’s harmonics --harmonics are integer multiples (twice, thrice, etc.) of a fundamental frequency. They are also quieter than the fundamental frequency. After determining the sound file’s content, you will record yourself saying the sound “Aaaaa” and then compare its complexity to that of the piano notes that you will have just finished analyzing.
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Musical Equations: 1. In the United States, there are two musical scales that are commonly used. One of those two is defined by having “Middle C” = 256 Hz (and "A" = 432Hz). In the other scale, "Middle A" = 440 Hz (and "C" = 261Hz) -- this second scale is what we will use in this lab. In older Renaissance era European works there are even more ways of defining the scales. (For more information please see: http://hypertextbook.com/facts/2003/DanielleDaly.shtml ) 2. Moving up one octave doubles the frequency 3. Moving down one octave halves the frequency 4. In western music there are 12 possible notes per octave. So to move up 1 note, multiply the frequency of the starting note by: 2 ( 1 / 12 ) , which is 1.0595 Or to go down one note, divide by that factor. To go up X notes, multiply by the factor: 2 ( X / 12) , and to go down by X notes, simply divide by that factor. 5. Since most software programs do not support "log base 2," we can use the following formula to produce the same result.
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