MainComponent.h

class MyAudioCallback : public AudioIODeviceCallback
{
public:
	MyAudioCallback() {}
	void audioDeviceIOCallback(const float **inputChannelData, int numInputChannels,
		float **outputChannelData, int numOutputChannels, int numSamples) override
	{
		for (int i = 0; i < numSamples; ++i)
		{
			float sample = jmap(m_rnd.nextFloat(), 0.0f, 1.0f, -0.1f, 0.1f);
			outputChannelData[0][i] = sample;
			outputChannelData[1][i] = sample;
		}
	}

	void audioDeviceAboutToStart(AudioIODevice *device) override
	{
	}

	void audioDeviceStopped() override
	{
	}
private:
	Random m_rnd;
};

class MainComponent   : public Component
{
public:
    //==============================================================================
    MainComponent()
    {
		m_adman.initialiseWithDefaultDevices(0, 2);
		m_adman.addAudioCallback(&m_acb);
		setSize (600, 400);
    }
	~MainComponent()
    {
		m_adman.removeAudioCallback(&m_acb);
    }
	void paint (Graphics& g) override
    {
        g.fillAll (getLookAndFeel().findColour (ResizableWindow::backgroundColourId));
		g.setFont (Font (16.0f));
        g.setColour (Colours::white);
        g.drawText ("Hello World!", getLocalBounds(), Justification::centred, true);
    }
	void resized() override
    {}
private:
	MyAudioCallback m_acb;
	AudioDeviceManager m_adman;
	
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MainComponent)
};