Audio Frequency Analyzer


"Audio Frequency Analyzer" is a powerful Real-Time Audio Analyzer (RTA) app for iPhone.

"Audio Frequency Analyzer" uses our proprietary signal processing technology to analyze incoming audio signals and provides a precision frequency response measurement and spectral visualization.

In the frequency range of 20kHz from 23Hz, the response of the measurement frequency can be displayed in the logarithmic FFT scale or 30 split band scale of 1/3 Octave.

"Audio Frequency Analyzer" is available in a variety of applications, such as sound room tuning, speaker settings, audio equipment testing, stage setting measurement, evaluation of sound mixing environment and Investigation of noise environment.

The latest version supports iOS 17 and improves stability and performance.



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Products Information

Version: 9.0
Release date: October 3, 2023 UTC
Size: 0.5 MB
Category: Utilities, Music
Compatibility: Compatible with iPhone. Requires iOS 16.6 or later.
Status: Now distributing.

Measurement display and input signal

"Audio Frequency Analyzer" measures the input acoustic signals, and displays the frequency spectrum in 30 split bands of 1/3 octave , or in the Logarithmic FFT scale.

Observation frequency range: 20 - 23000 Hz
Measurement display
FFT Scale: X-axis - log-scale frequency : 20 - 20000 Hz
1/3 Octave Scale: X-axis - Center frequency (Hz): 25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200,
250, 315, 400, 500, 630, 800, 1k, 1.25k, 1.6k, 2k, 2.5k, 3.15k, 4k, 5k, 6.3k, 8k, 10k, 12.5k, 16k, 20k
Measurement display Y-axis - Logarithmic amplitude (Ref-Level: 0dB/1V): Up to +30dB from -130dB


"Audio Frequency Analyzer" has the following features:

Optimized for iPhone, Compact code size.
High performance software design for Real Time Spectrum Audio Analyzing.
Frequency spectrum response measurement of 1/3 octave unit, 30 bands. (OCT)
FFT analyzer (FFT): 8192 points/frame
Logarithmic amplitude band: 70dB/band-width. minimum
Frequency display: 20 - 23000 Hz (X-axis)
Logarithmic amplitude display. (Y-axis)
Function of touch-scroll to adjust visible amplitude ranges.
Display measured value of 1/3 oct bands at OCT mode. (dB@OCT)
Function to change the graph slope at FFT mode. (Slope): -3dB/oct(less than 1kHz), + 3dB/oct(1kHz or higher)
Peak Hold function. (Hold)
Display response control. (Fast/Slow)
Reset of Measurement display position. (Scroll)
Snapshot of Measurement display. (Snap)
Calibration function at OCT mode. (Calibrate) : 1/3 octave band offset and overall offset setting.
Display Info view. (Info.)
Supports built-in microphone, headset microphone, and external digital audio connection.


"Audio Frequency Analyzer" can be very useful for a variety of applications including:

Frequency characterization evaluation of speakers and headphones
Testing and tuning audio amplifiers, equalizers and many other audio equipments
Stage setting measurement
Evaluation of sound mixing environment
Evaluation of car audio equipments installation
Various acoustic testing, and others

Important initial settings (iOS permissions)

In order for this app to work properly, it is necessary to make the following initial settings related to the iOS system.

Microphone access permission setting

At the initial startup after installing the app, the iOS system asks for permission to access the built-in microphone. In this case, you need to enable access to "Microphone".

If you have not enabled this setting, this app can not work by privacy restrictions of the iOS system. Please enable the access permission on the iOS setting, "Settings > Privacy & Security > Microphone".

Photos access permission setting

When the first time you save an image data with Snapshot, the iOS system asks for permission to access the "Photos" library. In this case, you need to enable access to "Photos".

If you have not enabled this setting, this app can not work by privacy restrictions of the iOS system. Please enable the access permission on the iOS setting, "Settings > Privacy & Security > Photos".

Top View

At the time of starting this app "Audio Frequency Analyzer", this topview will be displayed. All operations can be carried out in the topview screen.

The access permission to the built-in microphone will be confirmed from the iOS system at the first start-up. Please enable access to the built-in microphone.

Top View

The topview has Measurement Mode(OCT/FFT), Calibration(Calibrate), Measured oct value (dB@OCT), Peak Hold(Hold), Start/Stop, Display response(Fast/Slow), Scroll, Slope adjustment(Slope), Snapshot(Snap) and Info view(Info) at right side. In addition, it has the measurement display (TRACE DISPLAY) at left side. By touching scroll the screen up and down direction, you can easily change the display range.

Trace Display

TRACE DISPLAY is the image monitor that displays the frequency spectrum measurements. The display shows the amplitude on the Y-axis, and the frequency of the 1/3 octave scale or logarithmic FFT scale on the X-axis.

TRACE DISPLAY is visible in the amplitude range of 70dB. By Touch Scroll setting, you can be observed in the amplitude display area that is shifted at +30dB to -130dB. The default position is set to 0dB. By tapping "Scroll" button, you can return to the reference level of 0 dB.

Trace Display at 1/3 octave mode


Trace Display at FFT mode


"Start/Stop" is a function to control the measurement of Frequency Analyzer. Tap "Start" button to start measurement and tap again to stop. Available to verify the instantaneous measurement results.

Mode (OCT/FFT)

Measurement function has two measurement modes, 1/3 octave mode (OCT), or, FFT mode (FFT). You can select a measurement mode by tapping either mode. The default is set to 1/3 octave mode.

1/3 Octave mode

In 1/3 octave mode, you can measure the energy average value of each frequency band by frequency division in 1/3 octave x 30 bands. You can analyze spectrum in a specific frequency band, not the instantaneous frequency peak. It is suitable for more quantitative spectrum analysis.


FFT mode

In FFT mode, It will perform an instantaneous FFT measurement in all measurement frequency. It can measure the instantaneous frequency peak situations, such as cases where multiple harmonics are generated.



"Hold" is a display function that is held the accumulated peak level. The measurement value of 1/3 octave mode or FFT mode will always be displayed holding the maximum value.

In addition, in 1/3 octave mode, when ideal pink noise (-3dB/oct) is measured and displayed in HOLD, a flat frequency response is theoretically obtained in all frequency bands.




It is the display response control function. The display refreshing speed can be switched between "Fast" and "Slow". For example, if the input signal changes rapidly and the display is difficult to see, set it to "Slow".


When you tap "Scroll" button, TRACE DISPLAY will be initialized. Reference level of TRACE DISPLAY returns to 0dB. Please use ”Scroll" if you want to initialize the image display immediately or to undo the information display.


"Calibrate" is a function to set the measurement offset gain. It is effective only when measuring in 1/3 octave mode.

By adjusting the characteristics according to the external microphone used, high accuracy measurement can be realized.

If you tap "Calibrate" button, a setting window that can be set to gain correction value is displayed. The overall level value can be set in the range of -15 dB to +15 dB. Also, the offset value per 1/3 octave can be set independently in the range of -15 dB to +15 dB.

Calibration Overall level setting image

Offset value per 1/3 octave setting image

The 1/3 octave band offset level setting allows you to save two offset data. The saved data can also be reloaded.

Save offset data of 1/3 octave band (Save)

Load offset data of 1/3 octave band (Load)


By tapping the "dB@OCT" button, the response level for each band is displayed in the 1/3 octave band measurement, so it can assist for calibration adjustment.

Display measured value of 1/3 octave bands


In FFT mode, you can change the slope of the FFT graph by tapping the "Slope" button. Depending on the source to be observed, this slope adjustment (3dB/oct, center frequency 1kHz) can make the FFT graph display more visible.

FFT graph slope settings : -3dB/oct (less than 1kHz), +3dB/oct (1kHz or higher), center frequency 1kHz

Slope OFF

Slope ON (3dB/oct, center frequency 1kHz)


"Snap" is a snapshot function to save the measurement result image to the Photos (camera roll). The access permission to Photos will be confirmed from the iOS system at the first snapshot usage. Please enable access to Photos.

Snapshot image in 1/3 octave mode

Snapshot image in FFT mode

Information view

If you tap "Info" button, it will be displayed the usage description and product information.

By tapping "Close" button, it return to the measurement view.

Info view

Release Note

Audio Frequency Analyzer version 9.0 was released on October 3, 2023 UTC.

* Correspond to iOS 17.0. Improved internal processing and performance.

Audio Frequency Analyzer version 8.0 was released on November 29, 2022 UTC.

* Correspond to iOS 16.0, Renewed UI design, Performance improvement.

Audio Frequency Analyzer version 7.0 was released on December 23, 2021 UTC.

* Correspond to iOS 15.0, Renewed UI design. Added a new function to change the slope in the FFT graph, Improved stability.

Audio Frequency Analyzer version 6.1 was released on February 5, 2021 UTC.

* Correspond to iOS 12.5, Added the Peak Hold function at FFT mode, Improved stability.

Audio Frequency Analyzer version 6.0 was released on July 1, 2020 UTC.

* Correspond to iOS 12.4, Update of UI design, Minor bug fixes.

Audio Frequency Analyzer version 5.0 was released on January 23, 2019 UTC.

* Correspond to iOS 12.1, Update of UI design, Improved stability.

Audio Frequency Analyzer version 4.3 was released on May 21, 2018 UTC.

* Correspond to iOS 11.3, Improved stability.

Audio Frequency Analyzer version 4.2 was released on March 14, 2018 UTC.

* Performance improvement.

Audio Frequency Analyzer version 4.1 was released on February 22, 2018 UTC.

* Performance improvement.

Audio Frequency Analyzer version 4.0 was released on January 17, 2018 UTC.

* Correspond to iOS 11.2, Update of UI design, Performance improvement.

* Add the 1/3 octave band calibration function.

Audio Frequency Analyzer version 3.2 was released on March 4, 2016 UTC.

* Correspond to iOS 9.2, Performance improvement.

Audio Frequency Analyzer version 3.1 was released on January 16, 2016 UTC.

* Correspond to iOS 8.4, Update of UI design, Performance improvement.

* Add display response control function.

* Delete Monitor function.

Audio Frequency Analyzer version 3.0 was released on March 5, 2015 UTC.

* Correspond to iOS 8.1, Major Update. Changed UI design design, Performance improvement.

* Add Peak-hold function.

* Add Snapshot function.

Audio Frequency Analyzer version 2.1 was released on July 4, 2014 UTC.

* Add gain calibration function.

* Improved low frequency response.

* Optimized code.

Audio Frequency Analyzer version 2.0 was released on April 20, 2014 UTC.

* Correspond to iOS 7.1, Major Update. Performance improvement

* Changed UI design and App name.

* Add Function of Touch-Scroll to adjust visible amplitude ranges.

fo-Kannon Lite version 1.1 was released on November 27, 2013 UTC.

* Update for iOS 7.0, Redesign of UI, performance improvement

* Adjustment of frequency accuracy, Improvement of sensitivity

fo-Kannon Lite version 1.0 was released on August 31, 2013 UTC.


If you use an external digital audio interface via Lightning or USB interface, iOS device is input from the left channel. Please input of the accoustic signal out of the way to level-over by the gain adjustment carefully.
If the acoustic signal of high level is input from external microphone (via pin jack), iOS devices might be switched to the built-in microphone automatically. It is recommended that you should adjust the microphone gain very carefully.
At the time of the first access to Microphone and Photos after installing the app, you will be asked authorization to access them by the iOS system. If you have not enabled this setting, the app can not access them by privacy restrictions of the iOS system. Please enable the access permission on the iOS setting, "Settings > Privacy & Security > Photos or Microphone".

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