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For sound insulation or soundproofing (or acoustic shielding) means all those actions aimed at limiting the unwanted sound and noise transmission, usually by introducing sound-absorbing materials in the path of the sound waves. The application fields where insulation or soundproofing measures are necessary are many, including recording studios, rehearsal rooms, cinemas, and environments dedicated to audio-video, residential, offices, and public places, industry, […]

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Infrasound sometimes referred to as low-frequency sound, lower in frequency than 20 Hz or cycles per second of the “normal“ limit of human hearing (20 kHz). Infrasound is characterized by an ability to get around obstacles with little dissipation. The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down

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A hydrophone (Ancient Greek: ὕδωρ + φωνή, lit. ’water + sound’) is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones consist of a piezoelectric transducer that translates mechanical energy resulting from a change in pressure into electrical energy. Some piezoelectric materials, or transducers, can convert a sound into an electrical

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Acoustic refraction

The speed of propagation of sound waves can change either due to changes in temperature or due to changes in the molecular weight of the gas in which propagation occurs. The first effect is the one that occurs in practice: going to higher altitudes of the atmosphere the temperature decreases, then decreases the speed of

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Ultrasounds are mechanical sound waves. Unlike acoustic phenomena, the frequencies that characterize ultrasounds are higher than those normally heard by a human ear. The frequency conventionally used to discriminate acoustic waves from ultrasonic waves is set at 20 kHz up to several gigahertz, higher than the upper audible limit of human hearing (below 20 kHz in healthy young adults).

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Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. In general, diffraction is defined as the spreading or bending of waves as they pass round the edge of an obstacle or through an opening whose size is roughly the same as the wavelength of the waves. The disturbed waves

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Reflection is the change in direction (rebounding) of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Most objects are visible because of the light that reflects from them. The reflection of a body in motion is a particular case of impact. In the

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The sound is defined as a perturbation wavelike that typically propagates as an audible wave of pressure in an elastic medium (such as a gas, liquid, or solid) and which generates an auditory sensation. The wave phenomenon, associated with the sound, causes that the numerous particles of the medium in which it is transmitted to vibrate, thus

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Acoustic wave [sound wave]

Acoustic waves (also known as sound waves) are a type of longitudinal waves that propagate by means of adiabatic compression and decompression. Longitudinal sound waves are waves that have the same direction of vibration as their direction of travel. Important quantities for describing acoustic waves are sound pressure, particle velocity, particle displacement, and sound intensity. Acoustic waves

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Threshold shift

A threshold shift is an increase in the hearing threshold for a particular sound frequency. It means that the hearing sensitivity decreases and that it becomes harder for the listener to detect soft sounds. Threshold shifts can be temporary or permanent. A temporary threshold shift (TTS) is a temporary shift in the auditory threshold. It may occur suddenly after

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Threshold of hearing

Sound level measurements in decibels are generally referenced to a standard threshold of hearing at 1000 Hz for the human ear which can be stated in terms of sound intensity: \[I_0=10^{-12}\;\dfrac{\textrm{W}}{\textrm{m}^2}=10^{-16}\;\dfrac{\textrm{W}}{\textrm{cm}^2}\] or in terms of sound pressure: \[P_0=2\times 10^{-5}\;\dfrac{\textrm{N}}{\textrm{m}^2}\] This value has wide acceptance as a nominal standard threshold and corresponds to 0 decibels. It

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In chemistry, absorption (also called gas absorption, gas scrubbing, or gas washing) is the transfer of one or more species from the gas phase to a liquid solvent. The species transferred to the liquid phase are called solutes or absorbates. Absorption does not change the chemical species present in the system. Absorption is used to

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Building or architectural acoustics

The principles of physical acoustics are applied in construction to two very different problems. The first concerns concert halls, theaters, cinemas, and film, radio, and television studios; it consists of studying the volumetric and constructive characteristics of the hall, the building materials, and the architectural forms, in order to obtain good audibility at every point

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Musical acoustics

Musical acoustics is the branch of acoustics that deals with that part of physical acoustics that deals with the study of musical sounds, which are generally complex sounds, more or less rich in harmonics; the concepts of musical scales and the various intervals; the problems of physical acoustics related to the vibrations of strings and

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Psychoacoustics, the study of the physical effects of sound on biological systems, has been of interest since Pythagoras first heard the sounds of vibrating strings and of hammers hitting anvils in the 6th century BC, but the application of modern ultrasonic technology has only recently provided some of the most exciting developments in medicine. The domain of

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A scientist working in the field of acoustics is an acoustician. The application of acoustics to technology is called acoustical engineering. There is often a great deal of overlap and interaction between the interests of acousticians and acoustical engineers. There are many different types of acousticians. Here are a few examples:

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Acoustics is a branch of physics that deals with the study, generation, transmission, and effects of mechanical waves in gases, liquids, and solids, including topics such as vibration, sound, ultrasound, and infrasound. The ear itself is another biological instrument dedicated to receiving certain wave vibrations and interpreting them as sound. Among the most important phenomena

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