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A-weighting
A-weighting is a form of frequency weighting and the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured sound levels in an effort to account for the relative loudness perceived by the human ear, as the ear is less sensitive to low audio frequencies. It is employed by arithmetically adding a table of values, listed by octave or third-octave bands, to the measured sound pressure levels in dB. The resulting octave band measurements are usually added (logarithmic method) to provide a single A-weighted value describing the sound; the units are written as dB(A). Other weighting sets of values – B, C, D and now Z – are discussed below. The curves were originally defined for use at different average sound levels, but A-weighting, though originally intended only for the measurement of low-level sounds (aro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Weighting Curves (1)
A-weighting is a form of weighting, frequency weighting and the most commonly used of a weighting filter, family of curves defined in the International standard International Electrotechnical Commission, IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured sound levels in an effort to account for the relative loudness perceived by the human ear, as the ear is less sensitive to low audio frequencies. It is employed by arithmetically adding a table of values, listed by octave band, octave or third-octave bands, to the measured sound pressure levels in decibel, dB. The resulting octave band measurements are usually added (logarithmic method) to provide a single A-weighted value describing the sound; the units are written as dB(A). Other weighting sets of values – B, C, D and now Z – are discussed below. The curves were originally defined for use at different average sound levels, but A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighting Filter
A weighting filter is used to emphasize or suppress some aspects of a phenomenon compared to others, for measurement or other purposes. Audio applications In each field of audio measurement, special units are used to indicate a weighted measurement as opposed to a basic physical measurement of energy level. For sound, the unit is the phon (1 kHz equivalent level). Sound Sound has three basic components, the wavelength, frequency, and Speed of sound, speed. In sound measurement, we measure the loudness of the sound in decibels (dB). Decibels are logarithmic scale, logarithmic with 0 Dbx (noise reduction), dB as the reference. There are also a range of frequencies that sounds can have. Frequency is the number of times a sine wave repeats itself in a second. Normal auditory systems can usually hear between 20 and 20,000 Hz. When we measure sound, the measurement instrument takes the incoming auditory signal and analyzes it for these different features. Weighting fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITU-R 468 Noise Weighting
ITU-R 468 (originally defined in CCIR recommendation 468-4, therefore formerly also known as CCIR weighting; sometimes referred to as CCIR-1k) is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard, now referred to as ITU-R BS.468-4, defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests. It is currently maintained by the International Telecommunication Union who took it over from the CCIR. It is used especially in the UK, Europe, and former countries of the British Empire such as Australia and South Africa. It is less well known in the USA where A-weighting has always been used. M-weighting is a closely related filter, an offset version of the same curve, without the quasi-peak detector. Explanation The A-weighting curve was based on the 40 phon equal-loudness contour derived initially by Fletcher and Munson (1933). Originally inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Level Meter
A sound level meter (also called sound pressure level meter (SPL)) is used for acoustics, acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. The Diaphragm (acoustics), diaphragm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). This movement of the diaphragm, i.e. the sound pressure (unit Pascal (unit), pascal, Pa), is converted into an electrical signal (unit volt, volt, V). While describing sound in terms of sound pressure, a logarithmic conversion is usually applied and the sound pressure ''level'' is stated instead, in decibels (dB), with 0 dB SPL equal to 20 micropascals. A microphone is distinguishable by the voltage value produced when a known, constant root mean square sound pressure is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fletcher–Munson Curves
An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness contours. By definition, two sine waves of differing frequencies are said to have equal-loudness level measured in phons if they are perceived as equally loud by the average young person without significant hearing impairment. The Fletcher–Munson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by Harvey Fletcher and Wilden A. Munson, and reported in a 1933 paper entitled "Loudness, its definition, measurement and calculation" in the ''Journal of the Acoustical Society of America''. Fletcher–Munson curves have been superseded and incorporated into newer standards. The definitive curves are those defined in ISO 226 from the International O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighting
The process of frequency weighting involves emphasizing the contribution of particular aspects of a phenomenon (or of a set of data) over others to an outcome or result; thereby highlighting those aspects in comparison to others in the analysis. That is, rather than each variable in the data set contributing equally to the final result, some of the data is adjusted to make a greater contribution than others. This is analogous to the practice of adding (extra) weight to one side of a pair of scales in order to favour either the buyer or seller. While weighting may be applied to a set of data, such as epidemiological data, it is more commonly applied to measurements of light, heat, sound, gamma radiation, and in fact any stimulus that is spread over a spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decibel
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a Power, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whose level (logarithmic quantity), levels differ by one decibel have a power ratio of 101/10 (approximately ) or root-power ratio of 101/20 (approximately ). The strict original usage above only expresses a relative change. However, the word decibel has since also been used for expressing an Absolute scale, absolute value that is relative to some fixed reference value, in which case the dB symbol is often suffixed with letter codes that indicate the reference value. For example, for the reference value of 1 volt, a common suffix is "#Voltage, V" (e.g., "20 dBV"). As it originated from a need to express power ratios, two principal types of scaling of the decibel are used to provide consistency depending on whether the scaling refer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loudness
In acoustics, loudness is the subjectivity, subjective perception of sound pressure. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of physical attributes of sound to perceived loudness consists of physical, physiological and psychological components. The study of apparent loudness is included in the topic of psychoacoustics and employs methods of psychophysics. In different industries, loudness may have different meanings and different measurement standards. Some definitions, such as ITU-R BS.1770 refer to the relative loudness of different segments of electronically reproduced sounds, such as for broadcasting and cinema. Others, such as ISO 532A (Stevens loudness, measured in sones), ISO 532B (Eberhard Zwicker, Zwicker loudness), DIN 45631 and ASA/ANSI S3.4, have a more general scope and are often used to characterize loudness of environmental noise. More modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Power
Sound power or acoustic power is the rate at which sound energy is emitted, reflected, Acoustic transmission, transmitted or received, per unit time. It is defined as "through a surface, the product of the sound pressure, and the component of the particle velocity, at a point on the surface in the direction Normal (geometry), normal to the surface, Surface integral, integrated over that surface." The International System of Units, SI unit of sound power is the watt (W). It relates to the power of the sound force on a surface enclosing a sound source, in air. For a sound source, unlike sound pressure, sound power is neither room-dependent nor distance-dependent. Sound pressure is a property of the field at a point in space, while sound power is a property of a sound source, equal to the total power emitted by that source in all directions. Sound power passing through an area is sometimes called ''sound flux'' or ''acoustic flux'' through that area. Sound power level ''L''WA Reg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Industrial Noise
Occupational noise is the amount of acoustic energy received by an employee's auditory system when they are working in the industry. Occupational noise, or industrial noise, is often a term used in occupational safety and health, as sustained exposure can cause permanent hearing damage. Occupational noise is considered an occupational hazard traditionally linked to loud industries such as ship-building, mining, railroad work, welding, and construction, but can be present in any workplace where hazardous noise is present. Regulation In the US, the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) work together to provide standards and regulations for noise in the workplace. National Institute for Occupational Safety and Health (NIOSH), Occupational Safety and Health Administration (OSHA), Mine Safety and Health Administration (MSHA), Federal Railroad Administration (FRA) have all set standards on hazardous o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Dosimeter
A noise dosimeter (American English) or noise dosemeter (British English) is a specialized sound level meter intended specifically to measure the noise exposure of a person integrated over a period of time. It is often used to comply with Health and Safety regulations such as the Occupational Safety and Health (OSHA) 29 CFR 1910.95 Occupational Noise Exposure Standard or EU Directive 2003/10/EC. Noise Measurement Noise dosimeters measure and store sound pressure levels (SPL) and, by integrating these measurements over time, provide a cumulative noise-exposure reading for a given period of time, such as an 8-hour workday. Dosimeters can function as personal or area noise monitors. In occupational settings, personal noise dosimeters are often worn on the body of a worker with the microphone mounted on the middle-top of the person's most exposed shoulder. Area monitoring can be used to estimate noise exposure when the noise levels are relatively constant and employees are not mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
