   <span class="c1"># Spectrogram calculation</span>
    <span class="n">spec</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">zeros</span><span class="p">((</span><span class="n">win_len_half</span> <span class="o">+</span> <span class="mi">1</span><span class="p">,</span> <span class="n">num_of_frames</span><span class="p">),</span> <span class="n">dtype</span><span class="o">=</span><span class="nb">complex</span><span class="p">)</span>

    <span class="k