English vibration lesson

The transfer function (Frequency Response Function (FRF)) includes H1, H2, H3, and Hv estimation. MATLAB code is also included.

There are several types of transfer functions (Frequency Response Function (FRF)): H1 estimation, H2 estimation, H3 estimation, and Hv estimation. This article describes H1 estimation. MATLAB code is also included.

There are several types of transfer functions (Frequency Response Function (FRF)): H1 estimation, H2 estimation, H3 estimation, and Hv estimation. This article describes H2 estimation. It also explains a little about the coherence function (Coherebce Function). MATLAB code is also included.

伝達関数（周波数応答関数：Frequency Response Function(FRF)）には、H1推定、H2推定、H3推定、Hv推定というようにいくつか種類があります。 本記事ではH3推定とHv推定について説明します。MATLABのコードも載せています。

We often hear that "averaging can reduce the effect of noise." However, people who do not handle actual measurement data (people who do not conduct experiments) do not really understand this. The reason is that there is no error in the data we are dealing with in the first place. In this article, I would like to explain noise reduction (error reduction) by averaging. This is the first article on "averaging," so it is intended to give those who are studying averaging for the first time an idea of what it is all about. In the next and subsequent articles, I will introduce more technical details.

We use fft to analyze the frequency of vibration and noise, but just typing "fft" in MATLAB is not correct for frequency analysis of vibration and noise. Also, if a window function is used, the amplitude will be reduced and must be corrected back to its original value. This article provides fft function files that can be used for vibration and noise, including correction for window functions.

Not surprisingly, the auditory correction filter is represented by a function. Therefore, anyone can easily create filters. This article introduces the functions for the A-weighting , B, C, and D filters and discloses the code for these correction filters.

When identifying resonant frequencies and vibration modes, many people look at the FRF peak and say, "I wonder if this is somehow the resonant frequency." However, it is not always the case that (peak FRF frequency) = (resonant frequency). However, (peak FRF frequency) = (resonance frequency) does not necessarily hold true. This article explains how to identify the resonance frequency using the mode indicator function.

When identifying resonant frequencies and vibration modes, many people look at the FRF peak and say, "I wonder if this is somehow the resonant frequency." However, it is not always the case that (peak FRF frequency) = (resonant frequency). However, (peak FRF frequency) = (resonance frequency) does not necessarily hold true. This article explains how to identify the resonance frequency using the mode indicator function.

The coherence function is a measure of the reliability of the frequency response function (FRF). This article introduces the mathematical formulas for the coherence function, and with the most easily programmable formulas, we have created a MATLAB program and published the code for it. It also demonstrates the general characteristics of the coherence function based on examples.