callback.cpp

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

    void audioDeviceAboutToStart(AudioIODevice* device) override
    {
    }

    void audioDeviceStopped() override
    {
    }
    float noiseGain = 0.05f;
private:
    Random rng;
};