Analysis of speech Dr. Anil Kumar Vuppala IIIT Hyderabad Analysis - - PowerPoint PPT Presentation

Analysis of speech

• Dr. Anil Kumar Vuppala

IIIT Hyderabad

Analysis of speech

Representing speech signal on a digital computer

• Sampling and Quantization

Representing information present in speech

• Extraction of parameters

Method of analysis is application dependent

Types of Analysis based segment duration

• Segmental (10 – 50 ms)
• Short-time spectrum, formants, pitch
• Subsegmental (1 – 5 ms)
• Excitation source characteristics, glottal

closure

• Suprasegmental ( > 100 ms)
• Prosodic features - Intonation, duration,

energy contour

Preprocessing

Preemphasis

• Primarily used for emphasizing high

frequency components wrt low frequency

• High-pass filtering removes envelope

y(n)=s(n)−a∗s(n−1)

H ( z)=Y ( z) S( z) = 1 1−az−1

Short-time Analysis

Speech signal – quasistationary Block processing or short-time analysis Issues – window shape and size Methods

• Short-time spectrum analysis
• Filter bank analysis
• Spectrographic analysis
• Linear prediction analysis
• Cepstral analysis

Filter bank analysis: Nonlinear frequency scales

• Human ear is frequency selective
• Higher resolution at low frequencies, vice-versa

Spectrographic Analysis

Narrowband and Wideband

8

Linear prediction analysis

LP residual gives an estimate of the excitation source Normalize LP error (residual to signal energy ratio) is useful in the analysis of different sounds, V/NV detection Peaks in Hilbert enevlop of the residual signal correspond to the GCIs

Spectral Envelope via LP analysis

Cepstral Analysis

• Cepstrum is computed as IDFT of log-magnitude

spectrum

• Helps separate system and source information
• Provides a compact representation of the

spectral envelope

• Can be evaluated from short-time (DFT)

spectrum or LP spectrum.

Thank you