223015b phase 3: nyquist-diagram demo (kap1 folie 35 nyquist-theorem). drei vergleichs-cases mit derselben grundwelle (8 cycles über 880px svg): (1) aliasing rot f_s=0.9f, 8 sample-punkte sitzen mathematisch korrekt auf der welle und ergeben verbunden eine ganz andere langsamere kurve, (2) nyquist-grenze gelb f_s=2f, 16 punkte exakt auf peak/tal und zigzag-verbindung zeigt mathematisches minimum, (3) überabtastung grün f_s=8f mit 64 dichten punkten die der welle treu folgen wie eine CD. punkte mit python berechnet (y = 70 - 45*sin(2π*(x-20)/105) für jede sample-position). verdict erklärt 44,1 khz: ohr hört bis 20 khz, 2x20=40 plus 4,1 sicherheitsmarge

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<title>Nyquist-Shannon — wie oft muss man messen?</title>
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<h1>Nyquist-Shannon — wie oft müssen wir messen?</h1>
<div class="sub">Dieselbe Welle, drei Sample-Raten. Eine fällt durch, eine reicht knapp, eine ist sicher.</div>
<div class="cases">
<div class="case bad">
<div class="case-meta">
<div class="case-tag">Zu wenig</div>
<div class="case-name">Aliasing</div>
<div class="case-rate">f<sub>s</sub> = 0,9 · f</div>
<div class="case-note">Die Sample-Punkte sitzen auf der Welle — aber verbunden sehen sie aus wie eine <strong>ganz andere, langsamere</strong> Welle.</div>
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<div class="case-tag">Genau</div>
<div class="case-name">Nyquist-Grenze</div>
<div class="case-rate">f<sub>s</sub> = 2 · f</div>
<div class="case-note">Sample exakt auf <strong>Peak und Tal</strong>. Mathematisch reicht das — visuell sieht es kaputt aus.</div>
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<div class="case-tag">Sicher</div>
<div class="case-name">Überabtastung</div>
<div class="case-rate">f<sub>s</sub> = 8 · f</div>
<div class="case-note">Genug Punkte — die Welle wird Punkt für Punkt nachgezeichnet. So macht es eine CD.</div>
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<div class="verdict-q">f<sub>s</sub> ≥ 2 · f<sub>max</sub>. So einfach. So endgültig.</div>
<div class="verdict-a">Das Ohr hört bis <strong>20 kHz</strong>. 2 × 20 = 40 kHz. Die CD nimmt <code>44,1 kHz</code> — die 4,1 sind Sicherheits-Marge.</div>
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