# Technical Acoustics I

Lecturer (assistant) Gerhard Müller [L]Gerhard Müller [L]Julian Freisinger Sommersemester 2019 See TUMonline See TUMonline

### Objectives

Participating in this lecture enables the students to understand the basics of Technical Acoustics. Applying their knowledge on complex numbers, logarithm calculus, calculation of sound levels they are able to predict sound fields in the open space and within rooms. Furthermore they shall obtain a profound understanding based on a physical background for the mechanisms of radiation, absorption. An insight into the related partial differential equations is provided. Thus the students shall be able to apply their knowledge to a large variety of questions arising in the domain of structure borne sound and technical acoustics in their professional life.

### Description

In this module the basics of Technical Acoustics are illustrated and discussed starting from acoustic signals in time and frequency domain described by complex quantities. The key aspects of the perception of sound and of the physical superposition of different sources are treated in the following. The propagation of waves is explained with the help of the corresponding solution for the partial differential equation (PDE) for the plane wave leading to characteristic impedances and wave solutions. Intensity and sound power are addressed. In the following the propagation of sound in the open space is derived with an engineering approach taking energy considerations into account. The results area illustrated at the basis of selected measurement results. The propagation of structure borne sound on plates is explained at the basis of the corresponding PDEs. The coupling with the adjacent air is illustrated. Specific phenomena concerning the radiation of structures are derived and discussed. Thematic outline: Time Domain - Frequency Domain - Fourier Series - Fourier Transformation - Description of vibrations with the help of complex quantities Perception of Sound - Law of Weber-Fechner, pitch - Sound pressure level, effective value - Frequency dependent perception (A-B-C-Leveling) (modern standards) - Description of time dependent sound levels (Energy equivalent sound averaging/percentiles) Prediction of sound fields - Superposition of sound: coherent - incoherent sound - Propagation of waves: wave equation plane case, spherical and cylindrical waves - Velocity, intensity, sound power - Structure borne sound on plates - Sound fields caused by some special types of sound sources: monopoles, dipoles, radiation of plates (coincidence frequency), - Radiation efficiency