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Patrick Hangl
2025-10-01 17:11:52 +02:00
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5 changed files with 87 additions and 47 deletions

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@@ -49,12 +49,32 @@ During the description of transfer functions, the term ''filter'' was used but n
\label{fig:fig_lowpass}
\end{figure}
Examples for an adaptive filter is the Least-Mean-Square-Algorithm used for adaptive noise reduction, which will be introduced in the following chapters.
\subsection{Finite Impulse Response- and Infinite Impulse Response-filters}
\subsection{Filter designs}
Before we continue with the introduction to the actual topic of this thesis, ANR, two very essential filter designs need further explanation - the Finite Impulse Response- (FIR) and Infinite Impulse Response-filters (IIR).
\subsubsection{Finite Impulse Response-filters}
A Finite Impulse Respone Filter, commonly referred to as a ''Feedforward Filter'' is defined through the property, that it uses only present and past input values and not feedback from output samples - therefore the response of a FIR-filter reaches zero after a finite number of samples. Due to the fact, that there is no feedback, a FIR-filter offers unconditional stability, meaning that the filter response can´t diverge in any case. A disatavante to the FIR-filter desgin is the relatively slow frequency reaction compared to its IIR counterpart.
A Finite Impulse Respone filter, commonly referred to as a ''Feedforward Filter'' is defined through the property, that it uses only present and past input values and not feedback from output samples - therefore the response of a FIR-filter reaches zero after a finite number of samples. Due to the fact, that there is no feedback, a FIR-filter offers unconditional stability, meaning that the filter response converges, no matter how the coefficients are set. A disadvantage to the FIR-desgin is the relatively slow frequency response compared to its IIR counterpart.
\begin{equation}
\label{equation_fir}
y[n] = \sum_{k=1}^{M} b_kx[n-k]
\end{equation}
\begin{figure}[H]
\centering
\includegraphics[width=0.8\linewidth]{Bilder/fig_fir.jpg}
\caption{FIR-filter}
\label{fig:fig_fir}
\end{figure}
\subsubsection{Infinite Impulse Response-filters}
A Ininite Impulse Respone Filter, commonly referred to as a ''Feedback Filter'' does, in contrary to its FIR-counterpart, use past output samples in addition to current and past input samples - hterefore the response of a IIR-filter theoretically continues indefinitely.
A Ininite Impulse Respone filter, commonly referred to as a ''Feedback Filter'' does, in contrary to its FIR-counterpart, use past output samples in addition to current and past input samples - therefore the response of an IIR-filter theoretically continues indefinitely. This recursive nature allows IIR filter to achieve a sharp frequency response with significantly fewer coefficients than an equivalent FIR filter but it also opens up the possibility, that the filter-response diverges, depending on the set coefficients.
\begin{equation}
\label{equation_iir}
y[n] = \sum_{k=1}^{M} b_kx[n-k] - \sum_{k=1}^{N} a_ky[n-k]
\end{equation}
\begin{figure}[H]
\centering
\includegraphics[width=0.8\linewidth]{Bilder/fig_iir.jpg}
\caption{IIR-filter}
\label{fig:fig_iir}
\end{figure}
\subsection{Introduction to Adaptive Nose Reduction}

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