Audio / Spectrum Analyzer

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 frequency weighting. (A-weighting, C-weighting, Flat/Z-weighting)
- 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 (Sine, Triangle, Squire, Saw)
- Generates the noise signal (white noise, pink noise)
- Pitch meter display.


[Setting items]
1. Screen structure :
Screen configuration can be selected.
- Wave: Display waveform only.
- Spectrum: Display spectrum only.
- Vertical: Display waveform / spectrum vertically.
- Horizon: Display waveform / spectrum horizontally.

2. FFT size :
Selectable FFT size. (number of samples used when performing FFT)
1024, 2048, 4096, 8192

3. Window function :
Selectable window function (multiplication just before FFT) used for spectrum calculation.
Hanning, Hamming, Blackman, No window

4. Frequency Weighting :
Selectable frequency weighting.
- Flat (Z-weighting): No frequency weighting is applied.
- A-weighting: Frequency response that takes into account human hearing.
- C-weighting: Relatively flat response.

5. Spectrum X Scale Type :
Selectable the type of expressing the X direction (frequency) of the spectrum.
- Linear: Distributed at equal intervals
- Log: The intervals increase logarithmically

6. Spectrum Control Direction :
Select the zoom / scroll direction of the spectrum: X (frequency) or Y (amplitude).

7. Peak Hold :
Displays the results of holding the past maximum values ​​(peak values) of the spectrum.

8. Octave Analysis :
Displays the results of classifying the spectrum into octave bands.
Division method:
- FFT: Spectral display
- 1/12, 1/6, 1/3, 1 octave: Display divided into octave bands
Calculation method:
- Max: Displays the maximum spectrum value in each band
- Average: Displays the average spectrum value in each band

9. 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.

10. Generates the noise signal :
Set the noise signal to be generated.
- There are 2 types of noise. (White noise, pink noise)
- The volume can be adjusted.


[Other]
- Supports background color selection (black, white).
- Supports adjusting the waveform line width. (1 ~ 5 px)
- Supports spectrum bar color selection (solid, colorful).
- Supports Bluetooth connection policy selection (disabled, HFP, A2DP).
- Supports scaling of waveform/spectrum screens in the Y direction (magnification: 0.5 - 2.0).
- Supports scaling of spectrum screens in the X direction (magnification: 1.0 - 16.0).


[Information]
- The vertical line spacing in the waveform display is 2 mSec.
- The spectrum calculation uses the vDSP library.


If you need multi audio signals, please try "Multiple Tone Generator" from the link on the setting screen.
This app generates the audio signal of 6 ch (Up to 16 ch).

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