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Parametric Audio Equalizer for iOS Devices

This example shows how to use the Parametric EQ Filter block and the multibandParametricEQ System object™ from the Audio System Toolbox™ to implement a parametric audio equalizer model, that can run on your host computer or an Apple iOS device.


Parametric equalizers are used to adjust the frequency response of audio systems. For example, a parametric equalizer can compensate for biases introduced by specific speakers. Equalization is a primary tool in audio recording technologies.

In this example, you design a parametric audio equalizer in a Simulink® model. You can run your model on the host computer or an iOS device. The equalization algorithm is a cascade of three filters with tunable center frequencies, bandwidths, and gains. You can visualize the frequency response in real time while adjusting the parameters.

Required Products

Required Hardware

To run this example on iOS devices you need the following hardware:

  • iPhone, iPod or an iPad

  • Host computer with Mac OS X system

  • USB cable to connect the iOS device to host computer

Model Setup

The audioequalizeriOS model provides a choice of device (host computer or iOS device), and audio source (MATLAB workspace or microphone). You can choose the configuration by clicking the Configuration UI button.

Configuration UI:

Run Model on the Host Computer

When you choose to run the model on the host computer, a UI designed to interact with the simulation is provided and can be opened by clicking Host Tuning UI.

Host Tuning UI:

The UI allows you to tune the parameters of three filters individually, and view the frequency response in real time. You can also check the Bypass check box to compare the modified sound with the original sound.

Click the View Frequency Response button to visualize the filters frequency response.

Run Model on an Apple iOS Device

To run the model on your Apple iOS device, you need to first ensure that you have installed Simulink Support Package for Apple iOS Devices and that your iOS device is provisioned.

Once your iOS device is properly configured, use a USB cable to connect the device to your host computer.

You can choose to make an iOS standalone equalizer app by clicking the Deploy to hardware button on the Simulink Editor toolbar. After deployment, the app can run on your iOS device even when it is disconnected from the host computer. The parameter tuning UI displays on your iOS device screen, as shown below:

You can also run the model in External mode by clicking the Run button on the Simulink Editor toolbar. To run in External mode, the iOS device must stay connected to the host computer. This mode enables you to view the frequency response on the host computer while adjusting parameters on your iOS device. Frequency response will display on the host screen as follows:

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