Audio / Spectrum Analyzer

RTA (FFT / Octave Analysis)

This RTA app supports simultaneous display of "audio waveform" and "amplitude spectrum" (size of FFT calculation result for each frequency) for audio signals input from a microphone.
(FFT: Fast Fourier Transform, RTA: Real Time Analyzer)

[Features]
- Supports simultaneous display of waveform / spectrum.
- Supports orientation both portrait and landscape.
- Selectable configuration of "waveform" / "spectrum" display.
- Selectable FFT size.
- Selectable window function. (used in spectrum calculation)
- Selectable the type of expressing the X direction (frequency) of the spectrum. (Linear/Log)
- Displays the peak level and its frequency of the spectrum.
- Peak Hold (displays the results of holding past peak values of the spectrum).
- Octave Analysis (displays the spectrum divided into octave bands).
- Generates the audio signal (4 types of waveform)
- Pitch meter display.


[Setting items]
[1. View Type]
Select the display screen configuration.
- Wave: Display waveform only.
- Spectrum: Display spectrum only.
- Vertical: Display waveform / spectrum vertically.
- Horizon: Display waveform / spectrum horizontally.

[2. FFT size]
Select FFT size. (number of samples used when performing FFT)
1024, 2048, 4096, 8192
The smaller FFT size value, the faster the display updates, but the fewer frequencies the spectrum can be acquired.
The larger FFT size value, the slower the display updates, but the more frequencies the spectrum can be acquired.

[3. Sampling Rate]
Select sampling rate.
The spectrum frequency range is set according to the sampling rate (up to the Nyquist frequency).

[4. Spectrum Average (N Ave)]
Number of spectrum average for a display of spectrum. (init value: 1)
Higher value will make the spectrum less noisy and more smooth, at the cost of lower time resolution.

[5. Window Function]
Select the window function (multiplied immediately before performing the FFT).
- Hann: Hanning window
- Hamm: Hamming window
- Blkman: Blackman window
- None: No window function

[6. Frequency Weighting]
Select the frequency weighting. (Used when measuring sound pressure level with a sound level meter.)
- Flat (Z-weighting): No frequency weighting.
- A-weighting: Frequency response that takes into account human hearing.
- C-weighting: Relatively flat response that covers a wider frequency range than A-weighting.

[7. Peak Hold]
When ON is selected, displays the results of holding the past maximum values (peak values) of the spectrum.

[8. Octave Analysis]
Set the spectrum to be divided into octave bands.
Division method:
- FFT: Spectral display (conventional method)
- 1/12, 1/6, 1/3, 1 octave: Display divided into octave bands (the larger the value, the larger the band width)
Calculation method:
- Max: Displays the maximum spectrum value in each band
- Average: Displays the average spectrum value in each band

[9. Spectrum X Scale Type]
Select how the X-axis (frequency) of the spectrum is represented.
- Linear: Distributed at equal intervals
- Log: The intervals increase logarithmically

[10. Generates the audio signal]
Set the audio signal to be generated.
- There are 4 types of waveform. (Sine, Triangle, Squire, Saw)
- It can set the value of the frequency in 20Hz - 20000Hz.


[Other]
- Supports background color selection (black, white).
- Supports adjusting the waveform line width. (1 ~ 5 px)
- Supports spectrum bar color selection (solid, colorful).
- Supports scaling of waveform/spectrum screens in the Y direction.
- Supports scaling of spectrum screens in the X direction.