©copyright Raimo Olavi Toivonen 1982-2021. All rights reserved. Last updated on Jan 30, 2021.

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Works   Works before ISA

ISA software

FFT spectrograms in Hz/time scale

|X(k)|db (k=0...N/2-1) = 20log10|SUM(w(n)x(n)e-jk(2π/N)n)|, n=0...N-1. Signal x(n) = xa(nT), n=0...N-1, T is the sample period, xa= analog signal. If xa is the voltage signal of the microphone, then xa(nT) = kPa(nT), where Pa is the pressure and k is the constant factor. Hamming-window w(n) = 0.54-0.46cos(2πn/(N-1)).

The computation uses the decimation-in-time (DIT) computation method. Over the years, I have coded as a DSP man FFT spectrogram of the Intelligent Speech Analyser™ (ISA) program
(1) for the Texas 16-bit TMS320 signal processor family in machine language,
(2) for Motorola's 16 and 32-bit M68000 microprocessor families in machine language and C language,
(3) for IBM 600 Series 32-bit PowerPC Microprocessor Family in machine language and C language,
(4) for Intel 32-bit and 64-bit microprocessor families in C++ language.

Signal windowing is done with a Hamming window, a rectangular window or a Blackman-Harris window with more than 90 dB.

Analysis pictures I have coded from the very beginning in Neon object-oriented programming language.

Leveäkaistainen FFT-spektrogrammi Hz/time-asteikolla.

Wide band FFT spectrogram display in Hz-scale

Leveäkaistainen FFT-spektrogrammi Hz/time-asteikolla.

Narrow band FFT spectrogram display in Hz-scale

Kapeakaistainen FFT-spektrogrammi Hz/time-asteikolla.

Short time Wide band FFT spectrogram display in Hz-scale

Lyhytaikainen leveäkaistainen FFT-spectrogrammi Hz/time-asteikolla.

Short time Narrow band FFT spectrogram display in Hz-scale

Lyhytaikainen kapeakaistainen FFT-spectrogrammi Hz/time-asteikolla.

Short time Narrow band FFT spectrogram display in Hz-scale

Lyhytaikainen kapeakaistainen FFT-spectrogrammi Hz/time-asteikolla.