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Active noise control ( ANC ), also known as noise cancellation ( NC ), or active noise reduction ( ANR ), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in ...
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 ).
Architectural acoustics noise control practices include interior sound reverberation reduction, inter-room noise transfer mitigation, and exterior building skin augmentation. In the case of construction of new (or remodeled) apartments , condominiums , hospitals , and hotels , many states and cities have stringent building codes with ...
The median multiple indicator, recommended by the World Bank and the United Nations, rates affordability of housing by dividing the median house price by gross (before tax) annual median household income). [17] A common measure of community-wide affordability is the number of homes that a household with a certain percentage of median income can ...
Noise regulation. Noise regulation includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government. After the watershed passage of the United States Noise Control Act of 1972, [ 1] other local and state governments passed further regulations.
The noise reduction coefficient (commonly abbreviated NRC) is a single number value ranging from 0.0 to 1.0 that describes the average sound absorption performance of a material. An NRC of 0.0 indicates the object does not attenuate mid-frequency sounds, but rather reflects sound energy. This is more conceptual than physically achievable: even ...
Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance. [ 3][ 4] Changes in the immune system and birth defects have been also attributed to noise exposure. [ 5] Although age-related health effects ( presbycusis) occur naturally with age, [ 6] in ...
A close-up image of acoustic foam. Acoustic foam is an open celled foam used for acoustic treatment. It attenuates airbone sound waves, reducing their amplitude, for the purposes of noise reduction or noise control. [ 1] The energy is dissipated as heat. [ 2] Acoustic foam can be made in several different colors, sizes and thickness.