CHAPTER 10 Applications of Digital Signal Processing

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CHAPTER 10 Applications of Digital Signal
Processing

• Wang Weilian
• wlwang_at_ynu.edu.cn
• School of Information Science and Technology
• Yunnan University

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Outline

• Speech Signals Processing
• Dual-Tone Multifrequency Signal Detection

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Speech Signals Processing

• Speech Analysis
• parameterize the speech signal
• To reduce the bandwidth
• To characterize the speech signal with only a few
  features
• Speech Signal Processing is one of the kernel
  technologies in those fields as follows
  Information Superhighway, Multimedia, OAS (office
  automation system), Modern Communications System,
  Intelligent System and so on.

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Speech Signals Processing

• Speech Analysis time-domain
• data windowing

Windowing Calculation
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Speech Signals Processing

• Speech Analysis time-domain
• Energy
• Selecting 10ms 30ms as the length of the window
  in general

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Speech Signals Processing

• Speech Analysis time-domain
• The zero crossing rate ( ZCR )
• where

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Speech Signals Processing

• Speech Analysis time-domain
• Energy and ZCR

Energy and ZCR
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Speech Signals Processing

• Speech Analysis time-domain
• The Autocorrelation function
• If , then

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Speech Signals Processing

• Speech Analysis time-domain
• The Autocorrelation function

The block diagram of the autocorrelation function
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Speech Signals Processing

• Speech Analysis frequency-domain
• Fourier Transform and Spectrogram

The filter-explanation of the FT
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Speech Signals Processing

• Speech Analysis frequency-domain
• The spectrogram

The spectrogram
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Speech Signals Processing

• Speech Analysis frequency-domain
• Spectra analysis
• The power spectra ( energy density function )
• Complex Ceptrum
• Quefrency

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Speech Signals Processing

• Speech Analysis frequency-domain
• Linear Predictive
• The model of signal generation

Autoregressive Moving Average Model
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Speech Signals Processing

• Speech Analysis frequency-domain
• Linear Predictive
• G is the gain factor.
• U(z) / S(z) is the Z-Transform of input / output
  sequence

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Speech Signals Processing

• Speech Analysis frequency-domain

Linear Predictive ( autocorrelation method )
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Speech Signals Processing

• Speech Synthesis
• Formant Synthesis the transfer function of
  formants can be simulated by using a 2th-order
  digital filter generally.

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Speech Signals Processing

• Speech Recognition

Communication via Spoken Language
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Dual-Tone Multifrequency Signal Detection

• A DTMF signal consist of a sum of two tones with
  frequencies taken from two mutually exclusive
  groups of preassigned frequencies.
• Each pair of such tones represents a unique
  number or a symbol.

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Dual-Tone Multifrequency Signal Detection

• Decoding of a DTMF signal thus involves
  identifying the two tones in that signal and
  determining their corresponding number or symbol.
• The DTMF decoder computes the DFT samples closest
  in frequency to the eight DTMF fundamental tones
  and their respective second harmonics.
• The DFT length N determines the frequency spacing
  between the locations of the DFT samples and the
  time it takes to compute the DFT sample. The
  frequency corresponding to the DFT index ( bin
  number ) k is