aLec29_sound - Introduction to Embedded Microcomputer...

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Introduction to Embedded Microcomputer Systems Lecture 29.1 Jonathan W. Valvano . Recap Design a DAC Experimental method Output a sine wave Overview Use DAC to create sounds What are the fundamental limitations? Precision, Sampling rate, Memory size, Processor calculations Testing Need software to create sounds. Frequency is the pitch Amplitude is the loudness. Shape is the voice. Humans can hear from about 25 to 20,000 Hz. Middle A is 440 Hz Other notes on a keyboard are determined o 440 * 2 N/12 o "N" is number of notes up or down from middle A. Middle C is 261.6 Hz. music contains multiple harmonics period loudness pitch = 1/period ms 0.0 1.0 2.0 3.0 4.0 5.0 V -5 -4 -3 -2 -1 0 1 2 3 4 5 23Dec2006 10:18 kHz 0.0 0.5 1.0 1.5 2.0 2.5 3.0 -50 -40 -30 -20 -10 0 10 20 23Dec2006 10:18 period Figure 8.3. A waveform shape that generates a trumpet sound.
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Introduction to Embedded Microcomputer Systems Lecture 29.2 Jonathan W. Valvano 330 Hz 523 Hz 0.5s 0.5s 1.0s 330 Hz Figure 8.4. You can control the amplitude, frequency and duration of each note (not drawn to scale). 330 Hz
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aLec29_sound - Introduction to Embedded Microcomputer...

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