Software Based Acoustical Measurements
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Software-Based Acoustical Measurements
This textbook provides a detailed introduction to the use of software in combination with simple and economical hardware (a sound level meter with calibrated AC output and a digital recording system) to obtain sophisticated measurements usually requiring expensive equipment. It emphasizes the use of free, open source, and multiplatform software. Many commercial acoustical measurement systems use software algorithms as an integral component; however the methods are not disclosed. This book enables the reader to develop useful algorithms and provides insight into the use of digital audio editing tools to document features in the signal. Topics covered include acoustical measurement principles, in-depth critical study of uncertainty applied to acoustical measurements, digital signal processing from the basics, and metrologically-oriented spectral and statistical analysis of signals. The student will gain a deep understanding of the use of software for measurement purposes; the ability to implement software-based measurement systems; familiarity with the hardware necessary to acquire and store signals; an appreciation for the key issue of long-term preservation of signals; and a full grasp of the often neglected issue of uncertainty in acoustical measurements. Pedagogical features include in-text worked-out examples, end-of-chapter problems, a glossary of metrology terms, and extensive appendices covering statistics, proofs, additional examples, file formats, and underlying theory.
Vibration, Acoustics and Strain Measurement
This textbook provides a comprehensive description of a variety of vibration and acoustic pickups and exciters, as well as strain gauge transducers. It is an exhaustive manual for setting up basic and involved experiments in the areas of vibration, acoustics and strain measurement (using strain gauges only). It further serves as a reference to conduct experiments of a pedagogical nature in these areas. It covers the various theoretical aspects of experimental test rigs, as well as a description and choice of transducers/equipment. The fundamentals of signal processing theory, including the basics of random signals, have been included to enable the user to make a proper choice of settings on an analyser or measuring equipment. Also added is a description of modal analysis theory and related parameter extraction techniques. All chapters are provided with conceptual questions which will provoke the reader to think and gain a better understanding of the subjects. The textbook illustrates around fifty experiments in the areas of vibration, acoustics and strain measurements. Given the contents, this textbook is useful for undergraduate and postgraduate students in the areas of mechanical engineering, with applications that range from civil structures, architectural and environmental systems, and all forms of mechanical systems including transport vehicles and aircraft.
Directivity Patterns for Room Acoustical Measurements and Simulations
Author: Martin Pollow
language: en
Publisher: Logos Verlag Berlin GmbH
Release Date: 2015-09-09
The acoustics of rooms can be objectively described by the room impulse responses obtained for given transfer paths using measurement or simulation. In practice, the directionally dependent behavior of sources and receivers is often disregarded and thus assumed to be of omnidirectional type. In reality, however, these sources and receivers have specific directivity patterns, which are reported to induce audible differences. In this work a methodology to capture, analyze and process directivity patterns of sources and receivers is described. With the help of surrounding spherical microphone and loudspeaker arrays these directivity patterns are measured to be used in room acoustic applications. Room impulse responses with respect to specific directivity patterns can be realized using compact loudspeaker arrays with known directivity. Applying the results of directivity superposition to the set of measured room impulse responses, the acoustics for specific directivity patterns are found. Using a simulation of the room instead, source and receiver directivity patterns can be included in both wave based and particle based methods. The results of this work facilitate more authentic descriptions of room acoustics for specific source and receiver directivity patterns.