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Acoustic and Structural Impedance and Intensity
Published in Colin H. Hansen, Foundations of Vibroacoustics, 2018
As sound intensity is an energy based quantity, its measurement or calculation requires the determination of two independent quantities; namely, the acoustic pressure and the acoustic particle velocity, together with the relative phase between them.
Chapter 3 Physics of the Senses
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
We can profitably start with a review of some of the terms associated with the science of audition. Audition itself is the faculty or sense of hearing. Audiology is the study and measure of hearing, including the detection and definition of hearing defects. Acoustics is the science of sound. A pure-tone sound wave is one in which the oscillations of pressure and displacement can be described in terms of a simple sine wave. The pure-tone sound wave is described quantitatively by its frequency and intensity. The waveform of all other sounds can be built up from linear combinations of pure tones. A sound wave is described subjectively in terms of its pitch, loudness and quality.
Background
Published in Russ Martin, Sound Synthesis and Sampling, 2012
Acoustics is the science of sound. Sound is concerned with what happens when something vibrates. The vibration can be produced by vibrating vocal cords, wind whistling through a hole, a guitar string being plucked, a gong being struck, a loudspeaker being driven back and forth by an amplified signal, and more. Although most people think of sound as being carried only through the air, sound can also be transmitted through water, metals, wood, plastics and many other materials.
Concise review: aerodynamic noise prediction methods and mechanisms for wind turbines
Published in International Journal of Sustainable Energy, 2023
Vasishta Bhargava Nukala, Chinmaya Prasad Padhy
Sound waves are produced due to mechanical vibrations which can occur freely or caused by an external force excitation in the atmosphere. Noise is unwanted sound that is produced when there are pressure or velocity perturbations with respect to atmospheric pressure (ref acoustic pressure 20 µPa for air). Human ear can sense sound waves in atmosphere that vary in a logarithmic manner and a decibel scale is often used to measure sound level given by Equation (1) where prms is the root mean square pressure fluctuation, pref is the reference sound pressure, μPa. Noise can be analysed in either frequency or time domain depending on the type of mechanical or electrical systems. Fluid systems can exhibit vibrations analogous to mechanical and electrical systems caused by gravitational potential energy, kinetic energy and compressibility of fluid volume. Acoustics is a branch of science which deals with sound generation control and propagation, its effects on subjects which interact in atmosphere. On the other hand, computational aeroacoustics (CAA) deals with the use of application of numerical methods to analyse flow-induced noise more accurately. The problems posed on the accurate prediction of aerodynamic noise are the important issues such as turbulent intensity and length scale disparity. Conventional CAA methods only address a particular combination of these issues and not comprehensively. A sketch of the classification of CAA methods can be shown using Figure 1.
Acoustic behaviour of textile structures
Published in Textile Progress, 2021
Parikshit Paul, Rajesh Mishra, B. K. Behera
Acoustics is the section of physics that studies the propagation of mechanical waves in fluids, and solids, including vibration, sound, ultrasound, and infrasound. Its application is of value in all aspects of modern society, with the most obvious being in the audio industries and in noise control. The etymological source of ‘acoustic’ is from the Greek word ἀκουστικός (akoustikos), meaning ‘of or for hearing, ready to hear’ and that from ἀκουστός (akoustos), ‘heard, audible’, which in turn derives from the verb ἀκούω(akouo), ‘I hear’ (Morfey, 2001). The American National Standards Institute and the Acoustical Society of America in their standard ANSI/ASA S1.1-2013 (Raichel, 2000) define acoustics as:Science of sound, pertaining its production, transmission, and consequence, in conjunction with physiological and psychological effects.Those parameters of a room that, together, determine its character concerning auditory effects.
Mode-matching analysis of flexural trifurcated waveguide with porosity effects
Published in Waves in Random and Complex Media, 2022
Haleem Afsar, Mohammad Mahtab Alam
Acoustics is the scientific branch that studies the sound. It deals with sound formation, causing sound from source to receiver, detecting and perceiving sound. There are numerous applications of acoustics in various fields of life. Some of the major disciplines of acoustics are ecological acoustics, architectural acoustics, melodic acoustics, bioacoustics, structural acoustics , submerged acoustics, etc. Acoustics certainly has an enormous impact on other fields of science as well. Acoustics is the science of producing, controlling, reflecting, transmitting and receiving sound waves. Initially, this science was applied to control sound in various places, such as theatres, halls, arenas and in designing musical instruments. But, with the start of twentieth century, rapid advancement was made in this field and now it has numerous physical applications like in detecting objects in air and water, in controlling noise in automobiles, buildings and aircrafts, in diagnosing and treating many medical ailments and in discovering new archaeological sites, etc. Scattering and propagation of waves in a plane-parallel waveguide is one of the most difficult problems. Recent studies in the field of acoustics, theory of electromagnetic waves, the theory of elasticity and waves on water can be viewed through the references [1–7]. These problems are frequently governed by the Helmholtz equation, as well as soft/rigid and impedance type boundary conditions. Wiener–Hopf (WH) technique has been used to solve a variety of similar boundary value problems, for example, see [8–10]. However, in many circumstances, the channels or ducts have discontinuities in geometries or changes in material qualities. As in acoustics, the design of the silencer can include coating and/or abrupt geometric changes to the bounding surfaces to improve noise transmission. In such cases, a distinct spectrum of wave numbers occurs, and the WH approach is not always appropriate. As a result, there is a need to investigate an alternate technique capable of dealing with increasingly complex physical conditions while being mathematically simple.