如何处理来自FFT的NaN结果

我正在尝试实现一个函数，该函数采用wav文件，通过AForge的FFT运行100秒的音频。当我更改偏移量以更改我通过 FFT 计算的音频中的位置时，有时我会得到可以在图形中显示的结果，但大多数时候我会得到一个复杂的 NaN 数组。为什么会这样？

这是我的代码。

    public double[] test()
    {
        OpenFileDialog file = new OpenFileDialog();
        file.ShowDialog();
        WaveFileReader reader = new WaveFileReader(file.FileName);
        byte[] data = new byte[reader.Length];
        reader.Read(data, 0, data.Length);
        samepleRate = reader.WaveFormat.SampleRate;
        bitDepth = reader.WaveFormat.BitsPerSample;
        channels = reader.WaveFormat.Channels;
        Console.WriteLine("audio has " + channels + " channels, a sample rate of " + samepleRate + " and bitdepth of " + bitDepth + ".");

        float[] floats = new float[data.Length / sizeof(float)];
        Buffer.BlockCopy(data, 0, floats, 0, data.Length);
        size = 2048;
        int inputSamples = samepleRate / 100;
        int offset = samepleRate * 15 * channels;
        int y = 0;
        Complex[] complexData = new Complex[size];

        float[] window = CalcWindowFunction(inputSamples);
        for (int i = 0; i < inputSamples; i++)
        {
            complexData[y] = new Complex(floats[i * channels + offset] * window[i], 0);
            y++;
        }
        while (y < size)
        {
            complexData[y] = new Complex(0, 0);
            y++;
        }

        FourierTransform.FFT(complexData, FourierTransform.Direction.Forward);

        double[] arr = new double[complexData.Length];
        for (int i = 0; i < complexData.Length; i++)
        {
            arr[i] = complexData[i].Magnitude;
        }
        Console.Write("complete, ");
        return arr;
    }
    private float[] CalcWindowFunction(int inputSamples)
    {
        float[] arr = new float[size];
        for(int i =0; i<size;i++){
         arr[i] = 1;   
        }
        return arr;
    }