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Soundproofing
Soundproofing is any means of impeding sound propagation. There are several methods employed including increasing the distance between the source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles for Absorption (acoustics), absorption, or using active anti-noise sound generators. Acoustic quieting and noise control can be used to limit unwanted noise. Soundproofing can reduce the transmission of unwanted direct sound waves from the source to an involuntary listener through the use of distance and intervening objects in the sound path (see sound transmission class and sound reduction index). Soundproofing can suppress unwanted indirect sound waves such as Reflection (physics), reflections that cause Echo (phenomenon), echoes and resonances that cause reverberation. Techniques Absorption Sound-absorbing material controls reverberant sound pressure levels within a cavity, enclosure o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorption (acoustics)
In acoustics, absorption refers to the process by which a material, structure, or object takes in sound energy when sound, sound waves are encountered, as opposed to reflection (physics), reflecting the energy. Part of the absorbed energy is transformed into heat and part is transmitted through the absorbing body. The energy transformed into heat is said to have been 'Dissipation, lost'.Acoustic Absorbers and Diffusers: Theory, Design and Applicatio.CRC Press .2009.Peter D'Antoni When sound from a loudspeaker collides with the walls of a room, part of the sound's energy is reflection (physics), reflected back into the room, part is transmitted through the walls, and part is absorbed into the walls. Just as the acoustic energy was transmitted through the air as pressure differentials (or deformations), the acoustic energy travels through the material which makes up the wall in the same manner. Deformation causes mechanical losses via conversion of part of the sound energy into h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Transmission Class
Sound Transmission Class (or STC) is an integer rating of how well a building partition attenuates airborne sound. In the US, it is widely used to rate interior partitions, ceilings, floors, doors, windows and exterior wall configurations. Outside the US, the ISO Sound Reduction Index (SRI) is used. The STC rating very roughly reflects the decibel reduction of noise that a partition can provide. The STC is useful for evaluating annoyance due to speech sounds, but not music or machinery noise as these sources contain more low frequency energy than speech. There are many ways to improve the sound transmission class of a partition, though the two most basic principles are adding mass and increasing the overall thickness. In general, the sound transmission class of a double wythe wall (e.g. two block walls separated by a airspace) is greater than a single wall of equivalent mass (e.g. homogeneous block wall). Definition The STC or sound transmission class is a single number metho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Barrier
A noise barrier (also called a soundwall, noise wall, sound berm, sound barrier, or acoustical barrier) is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution. Noise barriers are the most effective method of mitigating roadway noise, roadway, railway, and industrial noise sources – other than cessation of the source activity or use of source controls. In the case of surface transportation noise, Noise mitigation#Roadways, other methods of reducing the source noise intensity include encouraging the use of Hybrid vehicles, hybrid and electric vehicles, improving Automotive aerodynamics, automobile aerodynamics and tire design, and choosing low-noise Pavement (material), paving material. Extensive use of noise barriers began in the United States after noise regulations were introduced in the early 1970s. History Noise barriers have been built in the United States since the mid-twentieth century, when vehicular traffic burgeoned. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Waves
In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges, allowing some to even hear ultrasounds. Definition Sound is defined as "(a) Oscillation in pressure, stress, particle displacement, particle velocity, etc., propagated in a medium with internal forces (e.g., elastic or viscous), or the superposition of such propagated oscillation. (b) Auditory sensation evo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Panel
Acoustic panels (also sound absorption panels, soundproof panels or sound panels) are sound-absorbing fabric-wrapped boards designed to control echo and reverberation in a room. Most commonly used to resolve speech intelligibility issues in commercial soundproofing treatments. Most panels are constructed with a wooden frame, filled with sound absorption material (mineral wool, fiber glass, cellulose, open cell foam, or a combination thereof) and wrapped with fabric. An acoustic board is a board made from sound absorbing materials, designed to provide sound insulation. Between two outer walls sound absorbing material is inserted and the wall is porous. Thus, when sound passes through an acoustic board, the intensity of sound is decreased. The loss of sound energy is balanced by producing heat energy. They are used in auditoriums, halls, seminar rooms, libraries, courts A court is an institution, often a government entity, with the authority to adjudicate legal disputes b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Propagation
In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges, allowing some to even hear ultrasounds. Definition Sound is defined as "(a) Oscillation in pressure, stress, particle displacement, particle velocity, etc., propagated in a medium with internal forces (e.g., elastic or viscous), or the superposition of such propagated oscillation. (b) Auditory sensation evok ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Quieting
Acoustic quieting is the process of making machinery quieter by damping vibrations to prevent them from reaching an observer. Machinery vibrates, causing sound waves in air, hydroacoustic waves in water, and mechanical stresses in solid matter. Quieting is achieved by absorbing the vibrational energy or minimizing the source of the vibration. It may also be redirected away from an observer. One of the major reasons for the development of acoustic quieting techniques was for making submarines difficult to detect by sonar. This military goal of the mid- and late-twentieth century allowed the technology to be adapted to many industries and products, such as computers (e.g. hard drive technology), automobiles (e.g. motor mounts), and even sporting goods (e.g. golf clubs). Aspects of acoustic quieting When the goal is acoustic quieting, a number of different aspects might be considered. Each aspect of acoustics can be taken alone or in concert so that the result is that the recepti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Resonance
Acoustic resonance is a phenomenon in which an acoustics, acoustic system amplifies sound waves whose frequency matches one of its own natural frequencies of vibration (its ''resonance frequencies''). The term "acoustic resonance" is sometimes used to narrow mechanical resonance to the frequency range of human hearing, but since acoustics is defined in general terms concerning vibrational waves in matter, acoustic resonance can occur at frequencies outside the range of human hearing. An acoustically resonant object usually has more than one resonance frequency, especially at harmonics of the strongest resonance. It will easily vibrate at those frequencies, and vibrate less strongly at other frequencies. It will "pick out" its resonance frequency from a complex excitation, such as an impulse or a wideband noise excitation. In effect, it is filtering out all frequencies other than its resonance. Acoustic resonance is an important consideration for instrument builders, as most a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Damping
In physical systems, damping is the loss of energy of an oscillating system by dissipation. Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. Examples of damping include viscous damping in a fluid (see viscous drag), surface friction, radiation, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators. Damping not based on energy loss can be important in other oscillating systems such as those that occur in biological systems and bikes (ex. Suspension (mechanics)). Damping is not to be confused with friction, which is a type of dissipative force acting on a system. Friction can cause or be a factor of damping. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium. A mass suspended from a spring, for example, might, if pulled and released, bounce up and down. On each bounce, the system tends to return to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Room Modes
Room modes are the collection of resonances that exist in a room when the room is excited by an acoustic source such as a loudspeaker. Most rooms have their fundamental resonances in the 20 Hz to 200 Hz region, each frequency being related to one or more of the room's dimensions or a divisor thereof. These resonances affect the low-frequency low-mid-frequency response of a sound system in the room and are one of the biggest obstacles to accurate sound reproduction. Mechanism of room resonances The input of acoustic energy to the room at the modal frequencies and multiples thereof causes standing waves. The nodes and antinodes of these standing waves result in the loudness of the particular resonant frequency being different at different locations of the room. These standing waves can be considered a temporary storage of acoustic energy as they take a finite time to build up and a finite time to dissipate once the sound energy source has been removed. Minimizing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temporal Coherence
Coherence expresses the potential for two waves to Wave interference, interfere. Two Monochromatic radiation, monochromatic beams from a single source always interfere. Wave sources are not strictly monochromatic: they may be ''partly coherent''. When interfering, two waves add together to create a wave of greater amplitude than either one (constructive Wave interference, interference) or subtract from each other to create a wave of minima which may be zero (destructive interference), depending on their relative phase (waves), phase. Constructive or destructive interference are limit cases, and two waves always interfere, even if the result of the addition is complicated or not remarkable. Two waves with constant relative phase will be coherent. The amount of coherence can readily be measured by the interference visibility, which looks at the size of the interference fringes relative to the input waves (as the phase offset is varied); a precise mathematical definition of the de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Consumer Reports - Product Testing - Headphones In Anechoic Chamber
A consumer is a person or a group who intends to order, or use purchased goods, products, or services primarily for personal, social, family, household and similar needs, who is not directly related to entrepreneurial or business activities. The term most commonly refers to a person who purchases goods and services for personal use. Rights "Consumers, by definition, include us all", said President John F. Kennedy, offering his definition to the United States Congress on March 15, 1962. This speech became the basis for the creation of World Consumer Rights Day, now celebrated on March 15. In his speech, John Fitzgerald Kennedy outlined the integral responsibility to consumers from their respective governments to help exercise consumers' rights, including: *The right to safety: To be protected against the marketing of goods that are hazardous to health or life. *The right to be informed: To be protected against fraudulent, deceitful, or grossly misleading information, advertising ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
