<!DOCTYPE html>
<svg width="300" height="200" viewBox="0 0 30 30">
  <defs>
    <filter id="f" x="0" y="0" width="100%" height="100%">
      <feTurbulence baseFrequency="0 3"/>
    </filter>
    <clipPath id="c">
      <rect width="30" height="30"/>
    </clipPath>
  </defs>
  <rect width="30" height="30" filter="url(#f)" clip-path="url(#c)"/>
</svg>