DSP in audio systems :

1
Introduction

• DSP in audio systems
• Music
• - Storage and manipulation.
• - Flexibility in final product
• - Artificial Reverberation
• Speech Generation
• - Digital Recording
• - Vocal tract simulation

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• Human hearing.
• Sound Quality Vs Data Rate.
• Companding.
• Non linear Audio Processing.
• High Fidelity Audio.
• Timbre.
• 7.Speech Synthesis Recognition

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The structure of human ear
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Human hearing

• The structure and functioning of human
  ear.
• Place principle.
• Volley principle.
• SPL-Sound Power Level.

5
Sound Quality Vs Data Rate.

• High Fidelity Music
• 44.1 kHz 16 bits 706k bits/sec.
• Telephone communication
• bandwidth 3.2 kHz,
• contains 8 out of 10 octaves
• Compressed speech
• sampling rate is 8 kHz
• Companding and LPC are used to reduce data
  rate.

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Companding
Mu Law mu 225.
A Law A 87.6
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Non Linear Processing

• Filtering of wideband noise in audio
  signals.
• Homomorphic Transform

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Surface of a compact disc
0.5 µm pit width
1.6 µm track spacing
Readout direction
3.5 µm max pit length
0.8 µm min pit length
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Timbre

• Characteristics of audio signal
• loudness, pitch, timbre
• The human ear is insensitive to the phase of
  the audio signal.
• The ear is very accustomed to hearing a
  fundamental plus harmonics.

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Logarithmic Distribution of frequency on the
keyboard of piano.
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Conclusion

• The principal human sense is hearing. People
  listen to music and speech. The DSP technology,
  with its algorithms, mathematics, and specialized
  techniques has made revolutionary changes in both
  these areas.

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