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Hello class,<br>
<br>
It seems that some of you are confused by the SPL formulas so here
are some elements to help you do it right:<br>
*The SPL curve we are asking you corresponds to <u>a vector with
one value for every frequency line</u> of the transforms.<br>
*The summation <img style="vertical-align: middle"
src="cid:part1.00060100.02060507@stanford.edu"
alt="$$\sum_{peak}$$"> present in the formula corresponds to a
summation that would include, in addition to a given line where a
sinusoid is present, neighboring lines where the energy of the
sinusoid would have "leaked". In the general case, when you want to
calculate the SPL value of any given line <img
style="vertical-align: middle;"
src="cid:part2.05040702.05070702@stanford.edu" alt="$$k$$"
height="16" width="10"> of an FFT/MDCT without discriminating
peaks and non-peaks, <u>the summation reduces to a single value</u>
<img style="vertical-align: middle"
src="cid:part3.09060007.09080500@stanford.edu" alt="$$|X(k)|^2$$">.<br>
<br>
Best,<br>
<pre class="moz-signature" cols="72">--
François Germain
Teaching Assistant / PhD Candidate
Center for Computer Research in Music and Acoustics (CCRMA)
Stanford University</pre>
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