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Psophometric Weighting
Psophometric weighting refers to any weighting curve used in the measurement of noise. In the field of audio engineering it has a more specific meaning, referring to noise weightings used especially in measuring noise on telecommunications circuits. Key standards are ITU-T O.41 ''ITU-T O.41'', October 1994 and C-message weighting as shown here. Use A major use of noise weighting is in the measurement of residual noise in audio equipment, usually present as hiss or hum in quiet moments of programme material. The purpose of weighting here is to emphasise the parts of the audible spectrum that ears perceive most readily, and attenuate the parts that contribute less to ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CCITT 0
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Communication Technology such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPEG-4 AVC for video compression, between its Member States, Private Sector Members, and Academia Members. The first meeting of the World Telecommunication Standardization Assembly (WTSA), the sector's governing conference, took place on 1 March of that year. ITU-T has a permanent secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland. The current director of the TSB is Chaesub Lee (of South Korea), whose first 4-year term commenced on 1 January 2015, and whose second 4-year term commenced on 1 January 2019. Chaesub Lee succeeded Malcolm Johnson of the United ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighting Curve
A weighting curve is a graph of a set of factors, that are used to 'weight' measured values of a variable according to their importance in relation to some outcome. An important example is frequency weighting in sound level measurement where a specific set of weighting curves known as A-, B-, C- and D-weighting as defined in IEC 61672 are used. Unweighted measurements of sound pressure do not correspond to perceived loudness because the human ear is less sensitive at low and high frequencies, with the effect more pronounced at lower sound levels. The four curves are applied to the measured sound level, for example by the use of a weighting filter in a sound level meter, to arrive at readings of loudness in phons or in decibels (dB) above the threshold of hearing (see A-weighting). Weighting curves in electronic engineering, audio and broadcasting Although A-weighting with a slow RMS detector, as commonly used in sound level meters is frequently used when measuring noise in audi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITU-T
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Communication Technology such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPEG-4 AVC for video compression, between its Member States, Private Sector Members, and Academia Members. The first meeting of the World Telecommunication Standardization Assembly (WTSA), the sector's governing conference, took place on 1 March of that year. ITU-T has a permanent secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland. The current director of the TSB is Chaesub Lee (of South Korea), whose first 4-year term commenced on 1 January 2015, and whose second 4-year term commenced on 1 January 2019. Chaesub Lee succeeded Malcolm Johnson (Director), Malc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Residual Noise
A residual is generally a quantity left over at the end of a process. It may refer to: Business * Residual (entertainment industry), in business, one of an ongoing stream of royalties for rerunning or reusing motion pictures, television shows or commercials * Profit (accounting), residuals that shareholders, partners or other owners are entitled to, after debtors are covered **Residual in the bankruptcy of insolvent businesses, moneys that are left after all assets are sold and all creditors paid, to be divided among ''residual claimants'' * Residual (or balloon) in finance, a lump sum owed to the financier at the end of a loan's term; for example Balloon payment mortgage Mathematics, statistics and econometrics * Residual (statistics) ** Studentized residual * Residual time, in the theory of renewal processes * Residual (numerical analysis) ** Minimal residual method ** Generalized minimal residual method * Residual set, the complement of a meager set * Residual property (mathem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Quality Measurement
Audio system measurements are a means of quantifying system performance. These measurements are made for several purposes. Designers take measurements so that they can specify the performance of a piece of equipment. Maintenance engineers make them to ensure equipment is still working to specification, or to ensure that the cumulative defects of an audio path are within limits considered acceptable. Audio system measurements often accommodate psychoacoustic principles to measure the system in a way that relates to human hearing. Subjectivity and frequency weighting Subjectively valid methods came to prominence in consumer audio in the UK and Europe in the 1970s, when the introduction of compact cassette tape, dbx and Dolby noise reduction techniques revealed the unsatisfactory nature of many basic engineering measurements. The specification of weighted CCIR-468 quasi-peak noise, and weighted quasi-peak wow and flutter became particularly widely used and attempts were made ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equal-loudness Contour
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 Orga ... [...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 Organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Measurement
In acoustics, noise measurement can be for the purpose of measuring environmental noise or measuring noise in the workplace. Applications include monitoring of construction sites, aircraft noise, road traffic noise, entertainment venues and neighborhood noise. One of the definitions of noise covers all "unwanted sounds". When sound levels reach a high enough intensity, the sound, whether it is wanted or unwanted, may be damaging to hearing. Environmental noise monitoring is the measurement of noise in an outdoor environment caused by transport (e.g. motor vehicles, aircraft, and trains), industry (e.g. machines) and recreational activities (e.g. music). The laws and limits governing environmental noise monitoring differ from country to country. At the very least, noise may be annoying or displeasing or may disrupt the activity or balance of human or animal life, increasing levels of aggression, hypertension and stress. In the extreme, excessive levels or periods of noise can have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Headroom (audio Signal Processing)
In digital and analog audio, headroom refers to the amount by which the signal-handling capabilities of an audio system can exceed a designated nominal level. Headroom can be thought of as a safety zone allowing transient audio peaks to exceed the nominal level without damaging the system or the audio signal, e.g., via clipping. Standards bodies differ in their recommendations for nominal level and headroom. Digital audio In digital audio, headroom is defined as the amount by which digital full scale (FS) exceeds the nominal level in decibels (dB). The European Broadcasting Union (EBU) specifies several nominal levels and resulting headroom for different applications. Analog audio In analog audio, headroom can mean low-level signal capabilities as well as the amount of extra power reserve available within the amplifiers that drive the loudspeakers. Alignment level Alignment level is an anchor point 9 dB below the nominal level, a reference level that exists throu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psophometric Voltage
Psophometric voltage is a circuit noise voltage measured with a psophometer that includes a CCIF-1951 weighting network. ''"Psophometric voltage"'' should not be confused with ''"psophometric emf," i.e.'', the emf in a generator or line with 600 Ω internal resistance. For practical purposes, the psophometric emf is twice the corresponding psophometric voltage. Psophometric voltage readings, ''V'', in millivolts, are commonly converted to dBm DBM or dbm may refer to: Science and technology * dBm, a unit for power measurement * DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB * Database Manager (DBM), a component of 1987's ''Extended Edi ...(psoph) by dBm(psoph) = 20 log10''V'' – 57.78. References * Electrical parameters Noise (electronics) Telecommunications engineering {{telecomm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rumble Measurement
A rumble is a continuous deep, resonant sound, such as the sound made by heavy vehicles or thunder. In the context of audio reproduction rumble refers to a low frequency sound from the bearings inside a turntable. This is most noticeable in low quality turntables with ball bearings. Higher quality turntables use slide bearings, minimizing rumble. Some phono pre-amplifiers implement a rumble filter, in an attempt to remove the noise. A heavier platter can also help dampen this. Rumble measurement is carried out on turntables (for vinyl recordings) which tend to generate very low frequency noise originating from the centre bearing and from drive pulleys or belts, as well as from irregularities in the record disc itself. It can be heard as low-frequency noise and becomes a serious problem when playing records on audio systems with a good low-frequency response. Even when not audible, rumble can cause intermodulation, modulating of the amplitude of other frequencies. The ‘un ... [...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 inco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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