Course detail

# Vibrations and Noise

Vibrations and noise are a general accompaniment to all machinery operations. The whole chain encompassing the vibration sources, transfer paths of the structure, noise emitters on the machine surface and ambient acoustic environment needs to be analyzed. We need to mainly focus on active methods of reducing vibrations and noise.
Basic areas of examination:
Spectra of vibro-acoustic quantities, experimental analysis,
biomechanics of the human voice and hearing, acoustic properties of closed areas.
Identification of sources of vibrations and noise, aerodynamic sources of noise.
Passive methods of noise reduction.
Active methods of noise reduction - vibroacoustic systems of machines, deterministic models (modelled by means of FEM ) for low-frequency noise), statistic models (solutions of high-frequency noise).

Learning outcomes of the course unit

To carry out the machine noise, sourer vibrations and noise identification, the modelling of dynamic phenomenon in the working processes, to realize the active and passive methods of vibrations and noise. By means of the machine noise analysis then to suggest the corresponding constructional and next arrangements, so that the dynamic machine properties would be influenced in desired direction.

Prerequisites

Fundamentals of acoustics: acoustic wave, acoustic quantities (pressure, intensity, power), acoustic signal spectra, experimental analysis of the acoustic quantities, acoustic fields, spectral and modal properties of acoustic cavities. Mathematics: matrix algebra, linear algebra, differential equations, basics of finite element method.

Co-requisites

Not applicable.

Recommended optional programme components

Not applicable.

Ohayon, R., Soize, C.: Structural Acoustic and Vibration, Academic Press, London, 1998 (EN)
Lyon, R. H., DeJong, R.G: Theory and Application of Statistical Energy Analysis, Butterwortth-Heinemann, Boston, 1995 (EN)
Beer, G., Smith, I., Duenser, Ch.: The Boundary Element Method with Proramming, Springer-Verlag, 2008 (EN)
Beranek, L.L.: Acoustics: Sound Fields and Transducers, Academic press, Oxford, 2012 (EN)

Planned learning activities and teaching methods

The course is taught through lectures explaining the basic principles and theory of the discipline.

Assesment methods and criteria linked to learning outcomes

The exam is written and oral.
Classification is made on the regulations to be used on VUT FSI.

Language of instruction

Czech, English

Work placements

Not applicable.

Aims

The target of the subject is theoretical and practical analyses of machine-tools noise, computer modelling their systems for reason to reduce the vibrations and acoustic energy radiation. An identification with the modern methods for analysis and solution of vibration and noise reduction when using the special programme systems for their solution - SYSNOISE, SEADS and etc.

Specification of controlled education, way of implementation and compensation for absences

Active participation in the course is controled individually according to the progression of work on the project.

#### Type of course unit

Lecture

20 hours, optionally

Teacher / Lecturer

Syllabus

1. Acoustic variables, linear and decibel representation
2. Spectra of acoustic variables : band pass, tracking,
multispectra
3.Acoustic properties of a closed areas
4.-5. Biomechanics of a human voice and hearing
6.Experimental identification of machine acoustic power
7.Aerodynamic noise sources, principles and examples
8.Passive methods of vibration and noise reduction
9.Principle of reactive dampers of pipe systems
10-11.Deterministic models of vibroacoustic machine systems:
- the coupling structure of vibroacoustic machine systems
- the methods of solution (FEM and BEM)
12-13. Statistical models of vibroacoustic systems (method SEA

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