Description - iOS app / Audio Frequency Analyzer

Audio Frequency Analyzer for iPhone


"Audio Frequency Analyzer" is a real-time spectrum audio analyzer (RTA) app for the iPhone. This app is a custom version that is optimized for iPhone based on the "fo-Kannon" iPad app.

"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 20Hz, 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 room tuning, speaker test, audio equipment test, stage setting measurement and evaluation of sound mixing environment.

By the version 3.1, the display response control function is now supported as new features.



Please to click the following link to download "Audio Frequency Analyzer" from App StoreTM. It will be open the download page on App StoreTM.

It will move to another site, download from Aplle Store

Installation of iTunes is required.
You can download this app, communications charges when connecting to the App Store will be borne by the customer.
* iPhone is a trademark of Apple Inc., registered in the U.S. and other countries.
* App Store is a service mark of Apple Inc.

Products Information

Version : 3.2
Release date : March 4, 2016 UTC
Size : 371 kB
Category : Utilities, Music
Recommendations : Requires iOS 9.2 or later.

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 - 20000Hz
Measurement display
FFT Scale: X-axis - log-scale frequency : 20 - 20000Hz
1/3 Octave Scale: X-axis - Center frequency(Hz): 25, 32, 40,50, 64, 80, 100, 125, 160, 200, 250, 320,
400, 500, 640, 800, 1k, 1.25k, 1.6k, 2k, 2.5k, 3.2k, 4k, 5k, 6.4k, 8k, 10k, 12.5k, 16k, 20k
Measurement display Y-axis - Logarithmic amplitude (Ref-Level: 0dB/1V): Up to +20dB from -120dB


"Audio Frequency Analyzer" has the following features:

Optimized for iPhone, Very compact code size.
High performance software design for Real Time Spectrum Audio Analyzing.
FFT: 4096points/frame
1/3 Octave (30 bands) display. (MODE: 1/3OCT.)
FFT display. (MODE: FFT)
Logarithmic amplitude band: 60dB/band-width. minimum
Function of Touch-Scroll to adjust visible amplitude ranges.
Display Pause function (PAUSE)
Calibration function (CALIB)
Peak hold functin (HOLD)
Display Response control function (SLOW)
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

How to use - 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

Operational area of two categories will be present in the topview.

The topview has the measurment control (RUN/PAUSE), peak hold setting (HOLD), 1/3 octave mode (1/3OCT), FFT mode (FFT), calibration setting (CALIB), snapshot (SNAP), display response (SLOW), display scale setting (SCALE) and infomation (i) 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.

How to use - 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. By MODE setting, you can select a measurement display of the frequency domain.

TRACE DISPLAY is visible in the amplitude range of 60dB. By Touch Scroll setting, you can be observed in the amplitude display area that is shifted at +20dB to -120dB. The default position is set to 0dB.

Trace Display at 1/3 Octave mode


How to use - Run/Pause

ss_run ss_pause

"RUN/PAUSE" is a function to control the measurement of Frequency Analyzer. Regardless of the setting state of the "RUN/PAUSE", measurement operation is working continuously. PAUSE (II icon) will suspend the update of the measurement display. Available to verify the instantaneous measurement results. If the RUN (triangle icon) button is tapped, the measurement display will be restarted.

How to use - Mode

ss_oct_mode ss_fft_mode

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

1/3 Octave band scale 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 Scale mode

In FFT scale 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.


How to use - Hold

ss_hold_enable ss_hold_on ss_hold_disable

HOLD is a display function that is held the accumulated peak level at 1/3 octave-band mode. In TRACE DISPLAY, the gain of each band will be displayed maximum value is always retained. In addition, the mode can not be selected at FFT mode.

How to use - Calib.


Calibration is a function to set the measurement offset gain. If you tap the "Calib." button, a text window that can be set to gain correction value is displayed. You can enter a correction value is set in the range from -20dB to +20dB on the keyboard.

Calibration image

How to use - Snap


Snapshot is a feature to save the measurement result image to the Photos (camera roll).

Snapshot image

How to use - Slow

ss_response_fast ss_response_slow

This is the display response control function. By tapping SLOW button, Trace Display will be show the measurement image slowly. Tap again, it returns to normal response.

How to use - Scale


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

How to use - Info


At the tap "i" button, it will be displayed on the product information.

If you tap the button "Support information", Safari will be started and you can view our support web page. In addition, if you tap the button "Other App information", App Store will be started and you find our iOS products information.

If tap "i" button again, it return to the measurement view.

Future update plan

Peak Search function


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

* Correspond to iOS 9.2, Performance improvement.

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

* 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.

* 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.

* Add gain calibration function.

* Improved low frequency response.

* Optimized code.

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

* 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.

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

* Adjustment of frequency accuracy, Improvement of sensitivity

fo-Kannon Lite version 1.0.0 was released on August 31, 2013.


If you use an external digital audio interface via DOCK/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 after installing the app, you will be asked permission to access them from the iOS. If you did not enable this setting on this time, it can not be access from the app by privacy restrictions of the iOS. Please enable slide switch of the app in the access permission of the iOS setting, "Settings > Privacy > Microphone".

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Contact us

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1. Application name
2. Device model
3. iOS version
4. Country you live
5. Details about your requests or problems.

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