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Impulse Noise (acoustics)
Impulse noise is a category of ( acoustic) noise that includes unwanted, almost instantaneous (thus impulse-like) sharp sounds (like clicks and pops)—typically caused by electromagnetic interference, scratches on disks, gunfire, explosions, pickleball play, and synchronization issues in digital audio. High levels of such a noise (200+ decibels) may damage internal organs, while impulses exceeding 180 decibels begin to present a risk of rupturing the tympanic membrane if hearing protection is not worn. The U.S. Department of Defense has established criteria for equipment that produces impulse noise at levels above 140 dB peak SPL and requires hearing protection be worn to prevent damage human ears. An impulse noise filter can enhance the quality of noisy signals to achieve robustness in pattern recognition and adaptive control systems. A classic filter used to remove impulse noise is the median filter, at the expense of signal degradation. Thus it's quite common to get b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustics
Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an Acoustical engineering, acoustical engineer. The application of acoustics is present in almost all aspects of modern society with the most obvious being the audio and noise control industries. Hearing (sense), Hearing is one of the most crucial means of survival in the animal world and speech is one of the most distinctive characteristics of human development and culture. Accordingly, the science of acoustics spreads across many facets of human society—music, medicine, architecture, industrial production, warfare and more. Likewise, animal species such as songbirds and frogs use sound and hearing as a key element of mating rituals or for marking territories. Art, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound. Acoustic noise is any sound in the acoustic domain, either deliberate (e.g., music or speech) or unintended. In contrast, noise in electronics may not be audible to the human ear and may require instruments for detection. In audio engineering, noise can refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as a hiss. This signal noise is commonly measured using A-weighting or ITU-R 468 weighting. In experimental sciences, noise can refer to any random fluctuations of data that hinders perception of a signal. Measurement Sound is measured based on the amplitude and frequency of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impulse Function
In mathematical analysis, the Dirac delta function (or distribution), also known as the unit impulse, is a generalized function on the real numbers, whose value is zero everywhere except at zero, and whose integral over the entire real line is equal to one. Thus it can be represented heuristically as \delta (x) = \begin 0, & x \neq 0 \\ , & x = 0 \end such that \int_^ \delta(x) dx=1. Since there is no function having this property, modelling the delta "function" rigorously involves the use of limits or, as is common in mathematics, measure theory and the theory of distributions. The delta function was introduced by physicist Paul Dirac, and has since been applied routinely in physics and engineering to model point masses and instantaneous impulses. It is called the delta function because it is a continuous analogue of the Kronecker delta function, which is usually defined on a discrete domain and takes values 0 and 1. The mathematical rigor of the delta function wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gunfire
A gunshot is a single discharge of a gun, typically a man-portable firearm, producing a visible flash, a powerful and loud shockwave and often chemical gunshot residue. The term can also refer to a ballistic wound caused by such a discharge. Multiple discharges of one or more firearms are referred to as gunfire. The word can connote either the sound of a gun firing, the projectiles that were fired, or both. For example, the statement "gunfire came from the next street" could either mean the sound of discharge, or it could mean the bullets that were discharged. It is better to be a bit more specific while writing however. "The sound of gunfire" or "we came under gunfire" would be more descriptive and prevent confusion. In the latter phrase, in particular, "fire" is used more (i.e. "under fire"), as both words hold the same general meaning within the proper context. Gunfire characteristics There are three primary attributes that characterize gunfire and hence enable the ... [...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] |
Defense Logistics Agency
The Defense Logistics Agency (DLA) is a combat support agency in the United States Department of Defense, United States Department of Defense (DoD). The agency is staffed by more than 26,000 civilian and military personnel throughout the world. Located in 48 states and 28 countries, DLA provides supplies to the military services and supports their acquisition of weapons, fuel, repair parts, and other materials. The agency also disposes of excess or unusable equipment through various programs. Through other Federal government of the United States, U.S. federal agencies, DLA also provides relief supplies to victims of natural disasters and humanitarian aid to refugees and internally displaced persons. Structure DLA is headquartered in Fort Belvoir, Virginia. It contains numerous offices responsible for supporting the overall agency. The agency has several major subordinate activities operating in the field: * DLA Aviation, headquartered in Richmond, Virginia, primarily supplies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Median Filter
The median filter is a non-linear digital filtering technique, often used to remove signal noise, noise from an image, signal, and video. Such noise reduction is a typical pre-processing step to improve the results of later processing (for example, edge detection on an image). Median filtering is very widely used in digital image processing because, under certain conditions, it preserves edges while removing noise (but see the discussion below for which kinds of noise), also having applications in signal processing. Algorithm description The main idea of the median filter is to run through the signal entry by entry, replacing each entry with the median of the entry and its neighboring entries. The idea is very similar to a moving average filter, which replaces each entry with the arithmetic mean of the entry and its neighbors. The pattern of neighbors is called the "window", which slides, entry by entry, over the entire signal. For one-dimensional signals, the most obvious window ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Synchronizer
An audio synchronizer is a variable audio delay used to correct or maintain audio-video sync or timing also known as lip sync error. See for example the specification for audio to video timing given in ATSC Document IS-191. Modern television systems use large amounts of video signal processing such as MPEG preprocessing, encoding and decoding, video synchronization and resolution conversion in pixelated displays. This video processing can cause delays in the video signal ranging from a few microseconds to tens of seconds. If the television program is displayed to the viewer with this video delay the audio-video synchronization is wrong, and the video will appear to the viewer after the sound is heard. This effect is commonly referred to as A/V sync or lip sync error and can cause serious problems related to the viewer's enjoyment of the program. Error correction To correct audio video sync problems, the video processing circuitry outputs a DDO (digital delay output) signal, whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crackling Noise
Crackling noise arises when a system is subject to an external force and it responds via events that appear very scale invariant, similar at many different scales. In a classical system there are usually two states, on and off. However, sometimes a state can exist in between. There are three main categories this noise can be sorted into: the first is ''popping'' where events at very similar magnitude occur continuously and randomly, e.g. popcorn; the second is ''snapping'' where there is little change in the system until a critical threshold is surpassed, at which point the whole system flips from one state to another, e.g. snapping a pencil; the third is ''crackling'' which is a combination of popping and snapping, where there are some small and some large events with a relation law predicting their occurrences, referred to as Universality (dynamical systems), universality. Crackling can be observed in many natural phenomena, e.g. crumpling paper, candy wrappers (or other elastic s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rustle Noise
Rustle noise is noise consisting of aperiodic pulses in a Poisson distribution, characterized by the average time between those pulses, known as rustle time (such as the mean time interval between clicks of a Geiger counter). Rustle time is determined by the fineness of sand, seeds, or shot in rattles, contributes heavily to the sound of sizzle cymbals, drum snares, drum rolls, and string drums, and makes subtle differences in string instrument sounds. Rustle time in strings is affected by different weights and widths of bows and by types of hair and rosin in strings. The concept is also applicable to flutter-tonguing, brass and woodwind growls, resonated vocal fry in woodwinds, and eructation sounds in some woodwinds. Robert Erickson suggests the exploration of accelerando-ritardando scales producible on some acoustic instruments and further variations in rustle noise "because this apparently minor aspect of musical sounds has a disproportionately large importance for higher l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Click (acoustics)
A click is a sonic artifact in sound and music production, characteristically impulse-like, that is to say, almost instantaneous, sharp, aharmonic sound. Analog recording artifact On magnetic tape recordings, clicks can occur when switching from magnetic play to record in order to correct recording errors and when recording a track in sections. On phonograph records, clicks are perceived in various ways by the listener, ranging from tiny 'tick' noises which may occur in any recording medium through ' scratch' and ' crackle' noise commonly associated with analog disc recording methods. Analog clicks can occur due to dirt and dust on the grooves of the vinyl record or granularity in the material used for its manufacturing, or through damage to the disc from scratches on its surface. Digital recording artifact In digital recording, clicks (not to be confused with the click track) can occur due to multiple issues. When recording through an audio interface, insufficient computer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
