S_TOOLS-STx provides a 2-channel Real Time Analyser to be called either as a stand alone application  in MS Windows NT/2000 and additionally in combination with the STx-Recorder in MS Windows XP and Vista/7. The STx RTA offers the following functions:

  • FFT-Amplitude Spectrum (STFT), Waterfall display and Spectrogram
  • Linear Prediction Coding (LPC) - smoothed  spectrum,  Waterfall display and Spectrogram
  • Cepstrum smoothed spectrum , Waterfall display and Spectrogram
  • Display amplitude spectrum minus Cepstrum smoothed spectrum (cp & sp.-cp).  
  • Display amplitude spectrum channel A and channel A-B
  • Linear and BARK frequency scaling
  • Selection of FFT-frame length (frequency resolution) and overlap (hopsize) over large ranges
  • Linear and Exponential Spectrum Averaging
  • Waveform display.

Waterfall Display: Sreenshot of the 2-channel Real Time Frequency Analyser (Frequency axis in BARK).


Fast Fourier Transform (FFT) - Amplitude Spectrum (white) with LPC-smoothed spectrum overlayed (yellow).


Note: the LPC-spectrum represents the all-pole model of unnasalized voiced speech signals. The spectral peaks indicate the resonance frequencies of the vocal tract (formants F1, F2, ...). The order of the model is specified by # of coefficients.

Spectrogram Display:


Averaging:  the averaging of consecutive amplitude spectra is specified in %.