Data AcQuisition And Real-Time AnalysisScope - Spectrum - Spectrogram - Signal Generator
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Spectrogram (Voiceprint) Screen Images
Spectrogram (Sgram) of spoken "DAQARTA", with approximate location of features shown in the Notes below it. The initial portion of the "DA" is distinguished by the upsweep of the first formant and the downsweep of the second, which then hold steady for the "A" portion of the syllable.
Note the stacked horizontal streaks in vowel regions, particularly prominent in the accented "QAR" syllable. Each line is a harmonic of the "glottal impulse" that excites the vocal tract at the fundamental frequency of the speaker's voice.
The waveform was recorded Direct-to-Disk (DDisk) with the built-in microphone of a laptop, using a 22050 Hz sample rate. The recording was then analyzed in Sgram mode with Trigger off and a Hann spectrum window applied. The Sgram file DDisk start position and Read Step Size were adjusted so that the utterance just filled the screen width.
Although this spectrogram was viewed "live" during recording, playback analysis allows for much finer temporal resolution by adjustment of Read Step Size.
Still finer temporal resolution can be obtained at a sacrifice of some frequency resolution by reducing the Spectrum Window Width from its default of 1024 samples. The spectrogram below was obtained from the one above by simply toggling from 1024 to 256:
In this view the individual harmonic frequencies are blurred together, but the glottal pulses that created them are easily resolved as a series of vertical lines in the "DA" and "TA" syllables. The spacing of the lines reflects the fundamental frequency of the male voice at about 100 pulses per second (10 msec line spacing).
The dB range of the spectrogram is shown via the color bar at the right edge of the trace area. By reducing the overall sensitivity (using the PgDn key), the brightness of the "QAR" syllable could have been reduced to allow its glottal pulses to be easily resolved.
The above spectrograms were created using the default Sgram Color Palette, but you can easily create any palette you desire using the built-in controls. You can save and load different palettes at any time, or change the palette that Daqarta loads at start-up.
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