Understanding Spectrogram of Speech Signal Using MATLAB Program

Dr A.R. Jayan is associate professor in ECE Department at RIT Kottayam, Kerala

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Parameters Nwt and Nst decide the resolving power of the spectrogram along time and frequency axes. Spectrograms obtained with Nwt values greater than 20ms are called narrowband spectrograms. Generally, these have a good frequency resolution. Frequency tracks appear as horizontal lines varying in intensity.

Narrowband spectrogram of vowel-consonant sound ‘as’
Fig. 6: Narrowband spectrogram of vowel-consonant sound ‘as’

When you lower the frame-duration parameter, you need to lower the frame-shift parameter also to avoid missing frames. A reduced value of frame duration results in a lower frequency resolution but a good time resolution. The spectrogram obtained with good time resolution and poor frequency resolution is called a wideband spectrogram. Narrowband spectrograms are useful for accurate frequency analysis of speech signals.

Wideband spectrogram of vowel-consonant sound ‘as’ | Speech signal
Fig. 7: Wideband spectrogram of vowel-consonant sound ‘as’

Wideband spectrograms are useful for accurate localisation of transient region onsets in the speech signal.

Narrowband spectrogram of sentence “You will mark as please..”
Fig. 8: Narrowband spectrogram of sentence “You will mark as please..”

Narrowband and wideband spectrograms for vowel-consonant sound ‘as’ are shown in Figs 6 and 7, respectively. Spectrograms (narrowband and wideband) for the sentence “You will mark as please” are shown in Figs 8 and 9, respectively. Readers are advised to experiment with different speech utterances and different values for Nwt, Nst, and nfft and to observe variations in spectrograms.

Wideband spectrogram of sentence “You will mark as please..”
Fig. 9: Wideband spectrogram of sentence “You will mark as please..”

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2 COMMENTS

  1. Please, how do i calculate MSE and SNR of ECG signal before and after noise?
    I need the result for about 300 sample frequencies.

    Thank you

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