Final Redesign - Implementation





MUSC 365 Introduction to Audio Recording is taught each spring semester. The redesign of the Basics of Digital Audio module will incorporated into this course beginning next spring. The instruction will include:
  • redesigned Keynote Slides
  • accompanying lecture
  • classroom discussion
  • audio examples


Audio Examples:
In order for students to grasp the direct correlation between sampling rate and audio frequency response and the effect of word length on dynamic range, as well as the effects of aliasing, I have prepared several short audio examples. As this is vastly important in teaching any kind of musical or audio course, audio examples can be considered a third perception channel in CTML, since they are neither verbal nor visual.

Effects of Sampling Rate:
The highest frequency a digital can support is half of the sampling rate. As you listen to each successive example, listen to how the high frequencies disappear. (Be sure to stop the playback of one file before starting another).

Sampling
Rate (kHz)
Highest
Frequency (kHz)
Audio File Player
44.1
22

33
16.5

22
11

11
5.5

5.5
2.75



Effects of Quantization Word Length:
The word length (number of bits per sample) determines the dynamic range of a digital system - the difference between the loudest and quietest sounds. Since all digital systems use the same maximum point, diminishing dynamic range is heard as increasing noise floor. As you listen to each successive example, listen to how the noise increases. (Be sure to stop the playback of one file before starting another).

Word Length
Dynamic Range (deciBels)
Audio File Player
16
96

12
72

10
60

8
48

6
36




Audible Effect of Aliasing:
Aliasing occurs when frequencies higher than half the sampling rate are sampled. This never happens in well designed audio systems, but it is good for students to be able to identify the audible effects.

Original Soundfile

Aliased Soundfile


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