APPLICATION OF UNCONVENTIONAL METHODS FOR FREQUENCY ANALYSIS IN ACOUSTICS

Akustika ◽  
2020 ◽  
Vol 36 (36) ◽  
pp. 25-32
Author(s):  
Jaroslav Smutný ◽  
Dušan Janoštík ◽  
Viktor Nohál
Keyword(s):  
Fourier Transform ◽  
Discrete Fourier Transform ◽  
Frequency Analysis ◽  
Mathematical Analysis ◽  
Measured Data ◽  
Application Area ◽  
Acoustic Response ◽  
Recommendations For Practice ◽  
Unconventional Methods ◽  
Frequency Area

The goal of this study is to familiarize a wider professional public with not fully known procedures suitable for processing measured data in the frequency area. Described is the use of the so-called Multi-taper method to analyze the acoustic response. This transformation belongs to a group of nonparametric methods outgoing from discrete Fourier transform, and this study includes its mathematical analysis and description. In addition, the use of respective method in a specific application area and recommendations for practice are described.

scholarly journals THE USE OF THE HILBERT HUANG TRANSFORMATION IN THE TESTING OF RAILWAY STRUCTURES

Akustika ◽  
2021 ◽  
pp. 29-35
Author(s):  
Jaroslav Smutný ◽  
Dušan Janoštík ◽  
Viktor Nohál
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Mathematical Analysis ◽  
Measurement Method ◽  
Calculation Procedure ◽  
Short Term ◽  
Transient Phenomena ◽  
Hilbert Huang Transform ◽  
Recommendations For Practice ◽  
Dynamic Phenomena

The aim of the paper is to introduce a less used method for the evaluation of non-stationary and especially transient phenomena in railway structures to the wider professional public. This method may find wide application in many technical and other fields. It is the so-called Hilbert-Huang transform. In this paper, its application in the study of dynamic phenomena occurring in a selected superstructure structure is shown. The calculation procedure of the presented transform differs from traditional tools, which include, for example, the short-term Fourier transform or the Wavelet transform. The paper includes a mathematical analysis and description of this transformation. Furthermore, the paper contains a description of the measurement method used, a discussion of the results obtained and recommendations for practice.

scholarly journals Variable Admittance Control Based on Human–Robot Collaboration Observer Using Frequency Analysis for Sensitive and Safe Interaction

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1899
Author(s):  
Hyomin Kim ◽  
Woosung Yang
Keyword(s):  
Fourier Transform ◽  
Discrete Fourier Transform ◽  
Frequency Analysis ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Infinite Impulse Response ◽  
User Intention ◽  
Low Frequency Motion ◽  
Frequency Behavior ◽  
Human Robot Collaboration

A collaborative robot should be sensitive to the user intention while maintaining safe interaction during tasks such as hand guiding. Observers based on the discrete Fourier transform have been studied to distinguish between the low-frequency motion elicited by the operator and high-frequency behavior resulting from system instability and disturbances. However, the discrete Fourier transform requires an excessively long sampling time. We propose a human–robot collaboration observer based on an infinite impulse response filter to increase the intention recognition speed. By using this observer, we also propose a variable admittance controller to ensure safe collaboration. The recognition speed of the human–robot collaboration observer is 0.29 s, being 3.5 times faster than frequency analysis based on the discrete Fourier transform. The performance of the variable admittance controller and its improved recognition speed are experimentally verified on a two-degrees-of-freedom manipulator. We confirm that the improved recognition speed of the proposed human–robot collaboration observer allows us to timely recover from unsafe to safe collaboration.

Frequency Analysis of Pulsed Optoacoustic Signals and the Application to Chemical Analysis

1982 ◽  
Vol 36 (2) ◽  
pp. 125-128 ◽  
Author(s):  
M. R. Fisher ◽  
D. M. Fasano ◽  
N. S. Nogar
Keyword(s):  
Fourier Transform ◽  
Chemical Analysis ◽  
Resonant Frequency ◽  
Discrete Fourier Transform ◽  
Frequency Spectrum ◽  
Frequency Analysis ◽  
Laser Excitation ◽  
Pulsed Laser ◽  
Signal Strength ◽  
Noise Sources

The optoacoustic signal generated via pulsed laser excitation-transducer detection is frequency analyzed via a discrete Fourier transform. The frequency spectrum is found to exhibit a pronounced maximum at the transducer resonant frequency. Use of this maximum as a measure of the optoacoustic signal strength allows for discrimination against window absorption and various electrical and mechanical noise sources.

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