<script type="text/x-red" data-help-name="AudioAnalyzeFFT1024"> <h3>Summary</h3> <div class=tooltipinfo> <p>Compute a 1024 point Fast Fourier Transform (FFT) frequency analysis, with real value (magnitude) output. The frequency resolution is 43 Hz, useful detailed for audio visualization.</p> </div> <h3>Audio Connections</h3> <table class=doc align=center cellpadding=3> <tr class=top><th>Port</th><th>Purpose</th></tr> <tr class=odd><td align=center>In 0</td><td>Signal to convert to frequency bins</td></tr> </table> <h3>Functions</h3> <p class=func><span class=keyword>available</span>();</p> <p class=desc>Returns true each time the FFT analysis produces new output data. </p> <p class=func><span class=keyword>read</span>(binNumber);</p> <p class=desc>Read a single frequency bin, from 0 to 511. The result is scaled so 1.0 represents a full scale sine wave. </p> <p class=func><span class=keyword>read</span>(firstBin, lastBin);</p> <p class=desc>Read several frequency bins, returning their sum. The higher audio octaves are represented by many bins, which are typically read as a group for audio visualization. </p> <p class=func><span class=keyword>averageTogether</span>(number);</p> <p class=desc>This function does nothing. The 1024 point FFT always updates at approximately 86 times per second. </p> <p class=func><span class=keyword>windowFunction</span>(window);</p> <p class=desc>Set the window function to be used. AudioWindowHanning1024 is the default. Windowing may be disabled by NULL, but windowing should be used for all non-periodic (music) signals, and all periodic signals that are not exact integer division of the sample rate. </p> <h3>Examples</h3> <p class=exam>File > Examples > Audio > Analysis > FFT </p> <p class=exam>File > Examples > Audio > Analysis > SpectrumAnalyzerBasic </p> <h3>Notes</h3> <p>The raw 16 bit output data bins may be access with myFFT.output[num], where num is 0 to 511.</p> <p>TODO: caveats about spectral leakage vs frequency precision for arbitrary signals</p> <p>Window Types: <ul> <li><span class=literal>AudioWindowHanning1024</span> (default)</li> <li><span class=literal>AudioWindowBartlett1024</span></li> <li><span class=literal>AudioWindowBlackman1024</span></li> <li><span class=literal>AudioWindowFlattop1024</span></li> <li><span class=literal>AudioWindowBlackmanHarris1024</span></li> <li><span class=literal>AudioWindowNuttall1024</span></li> <li><span class=literal>AudioWindowBlackmanNuttall1024</span></li> <li><span class=literal>AudioWindowWelch1024</span></li> <li><span class=literal>AudioWindowHamming1024</span></li> <li><span class=literal>AudioWindowCosine1024</span></li> <li><span class=literal>AudioWindowTukey1024</span></li> </ul> </p> <p>1024 point FFT has a peak CPU usage of approx 52% on Teensy 3.1. Average usage is much lower. Future versions might distribute the load more evenly over time.... </p> </script> <script type="text/x-red" data-template-name="AudioAnalyzeFFT1024"> <div class="form-row"> <label for="node-input-name"><i class="fa fa-tag"></i> Name</label> <input type="text" id="node-input-name" placeholder="Name"> </div> </script>