Incorrectly generated wav file due to improper usage of sndfile library

Question

Even though the text file to which I saved all the samples contains (possibly) proper samples, the sound file generated using the same set of data contains only the noise. The code responsible for writing the wav file:

void Filter::generateFrequencySound()
{
    SNDFILE * outfile;
    SF_INFO sfinfo;// = {0};

    memset (&sfinfo, 0, sizeof (sfinfo)) ;

    //preparing output file
    sfinfo.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16;
    sfinfo.channels = 1;
    sfinfo.samplerate = 44100;

    std::cout << "Trying to save samples to a file" << std::endl;

    const char* path = "FilterInFrequency.wav";

    outfile = sf_open(path, SFM_WRITE, &sfinfo);

    if(!(outfile))
    {
        std::cout << "Failed to create output file" << std::endl;
        sf_perror(outfile);
        return;
    }

    unsigned long savedSamples = sf_write_double( outfile,
                                                  outputOfFrequencyFiltration,
                                                  bufferSize);

    if(savedSamples > bufferSize)
    {
        std::cout << "Failed to save all samples into outflie. Number of sampels " << savedSamples << std::endl;
        sf_close(outfile);
        return;
    }

    sf_close(outfile);

    QSound::play("FilterInFrequency.wav");

}

The code responsible for writing samples into a text file:

 QFile file("finalResult_1.txt");

    if(!file.open(QIODevice::WriteOnly))
    {
        std::cout << "something went wrong";
        exit(16);
    }

    QTextStream outstream(&file);

    for(unsigned long i = 0; i < bufferSize; i++)
    {
        QString line = QString::number(outputOfFrequencyFiltration[i]);
        outstream << line << "\n";
    }

    file.close();

Comparison of divergence between wav and plotted text file can be seen in the attached image. The plots have been created using the same amount of data (~20500 samples- ~10% of the output file). The file size is same for both plots.

What could be the possible reason for the differences?

textfile wavfile