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Acoustics ( a-kōōs'tĭks ). Those phenomena which one detects by the ear are generally studied together under the head of acoustics. But whenever any sound is heard we find that somewhere in the neighborhood there is what we call a sound- ing body, and this is always found to be a body in rapid vibration.
The New Student's Reference Work/Acoustics
Acoustics (from Greek ακουστικός pronounced akoustikos meaning "of or for hearing, ready to hear") is the science that studies sound, in particular its production, transmission, and effects. The science of acoustics has many applications which are dependent upon the nature of the sound that is to be produced, transmitted or controlled. In the case of a desirable sound, such as music, the main application of acoustics is to make the music sound as good as possible.
Acoustics - Wikibooks
Wave equation
The wave equation is an important second-order linear partial differential equation for the description of waves – as they occur in physics – such as sound waves, light waves and water waves. It arises in fields like acoustics , electromagnetics , and fluid dynamics . Historically, the problem of a vibrating string such as that of a musical instrument was studied by Jean le Rond d'Alembert , Leonhard Euler , Daniel Bernoulli , and Joseph-Louis Lagrange . [ 1 ] [ 2 ] [ 3 ] [ 4 ]Wave
In physics a wave is a disturbance or oscillation that travels through space and matter, accompanied by a transfer of energy . Wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass transport. They consist, instead, of oscillations or vibrations around almost fixed locations. Waves are described by a wave equation which sets out how the disturbance proceeds over time.
Surface acoustic wave
Experimental image of surface acoustic waves on a crystal of tellurium oxide. [1] A surface acoustic wave ( SAW ) is an acoustic wave traveling along the surface of a material exhibiting elasticity , with an amplitude that typically decays exponentially with depth into the substrate. [ edit ] Discovery SAWs were first explained in 1885 by Lord Rayleigh , who described the surface acoustic mode of propagation and predicted its properties in his classic paper. [ 1 ] Named after their discoverer, Rayleigh waves have a longitudinal and a vertical shear component that can couple with any media in contact with the surface. This coupling strongly affects the amplitude and velocity of the wave, allowing SAW sensors to directly sense mass and mechanical properties. [ edit ] SAW devices
Sound reflection board Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles , or using active antinoise sound generators.
Soundproofing
Sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure caused by a sound wave . In air, sound pressure can be measured using a microphone , and in water with a hydrophone . The SI unit for sound pressure p is the pascal (symbol: Pa). Sound pressure diagram: 1. silence, 2. audible sound, 3. atmospheric pressure, 4. instantaneous sound pressure Sound pressure level (SPL) or sound level is a logarithmic measure of the effective sound pressure of a sound relative to a reference value. It is measured in decibels (dB) above a standard reference level.
Plane P-wave Representation of the propagation of a P-wave on a 2d grid (empirical shape) P-waves are a type of elastic wave , called seismic waves in seismology, that can travel through a continuum . The continuum is made up of gases (as sound waves), liquids, or solids, including the Earth .
Pressure Wave
Noise pollution
Noise pollution is displeasing or excessive noise that may disrupt the activity or balance of human or animal life. The word noise is cognate with the Latin word nauseas , which means disgust or discomfort. [ 1 ] The source of most outdoor noise worldwide is mainly caused by machines and transportation systems , motor vehicles , aircrafts , and trains . [ 2 ] [ 3 ] Outdoor noise is summarized by the word environmental noise . Poor urban planning may give rise to noise pollution, since side-by-side industrial and residential buildings can result in noise pollution in the residential areas.
Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, urban planning through zoning codes , [ 1 ] and occupational noise control. Roadway noise and aircraft noise are the most pervasive sources of environmental noise worldwide, and little change has been effected in source control in these areas since the start of the problem, [ citation needed ] a possible exception being the development of hybrid and electric vehicles . Social activities may generate noise levels that consistently affect the health of populations residing in or occupying areas, both indoor and outdoor, near entertainment venues that feature amplified sounds and music that present significant challenges for effective noise mitigation strategies.
Noise mitigation
Doppler effect
Change of wavelength caused by motion of the source An animation illustrating how the Doppler effect causes a car engine or siren to sound higher in pitch when it is approaching than when it is receding. The pink circles are sound waves.Computer generated intensity pattern formed on a screen by diffraction from a square aperture. Generation of an interference pattern from two-slit diffraction. Computational model of an interference pattern from two-slit diffraction.
Diffraction
Audiology (from Latin audīre , "to hear"; and from Greek -λογία , -logia ) is the branch of science that studies hearing, balance, and related disorders. Its practitioners, who treat those with hearing loss and proactively prevent related damage are audiologists. Employing various testing strategies (e.g. hearing tests , otoacoustic emission measurements, videonystagmography, and electrophysiologic tests), audiology aims to determine whether someone can hear within the normal range, and if not, which portions of hearing (high, middle, or low frequencies ) are affected and to what degree. If an audiologist determines that a hearing loss or vestibular abnormality is present he or she will provide recommendations to a patient as to what options (e.g. hearing aid , cochlear implants , surgery , appropriate medical referrals) may be of assistance.
Audiology
In physics , the acoustic wave equation governs the propagation of acoustic waves through a material medium. The form of the equation is a second order partial differential equation . The equation describes the evolution of acoustic pressure
Acoustic wave equation
Room acoustics describes how sound behaves in an enclosed space. The way that sound behaves in a room can be broken up into roughly four different frequency zones: The first zone is below the frequency that has a wavelength of twice the longest length of the room. In this zone, sound behaves very much like changes in static air pressure. Above that zone, until the frequency is approximately 11,250(RT60/V) 1/2 , wavelengths are comparable to the dimensions of the room, and so room resonances dominate. The third region which extends approximately 2 octaves is a transition to the fourth zone.