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Deepak Kumar Sound engineer Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.  Microphone placement icrophoneplacement plays an important part in the tonal rendition of the sounds. Bearingthis face constantly in the mind would save the pitfall of compensating forplacement error by processing device .For example; placing a microphone off theaxis of a voice and trying to get sharpness by the equalizer is a bad idea. Theaim should to start with a clean signal from the microphone. Being on axis withthe source, avoiding low pickup of sound, avoiding overloading and wind blows,are desirable of a good microphone placement .even if permitted by themicrophone sensitivity ,going rather too close to a sound source should beavoided . This helps to prevent proximity effect which manifests itself as anabnormal reproduction of frequencies of the source with reference to eachother. In addition, If the source is a voice, breathing, lip smearing and nasalsound may be picked up by an extremely close placement. A schematic showing the relationship between dBu (the voltagesource) and dBm (the power dissipated as heat bythe 600 Ω resistor) dBV dB(1 VRMS) – voltagerelative to 1 volt, regardless of impedance.[2] dBu or dBv dB(0.775VRMS) – voltage relativeto 0.775 volts.[2]Originally dBv, it was changed to dBu to avoid confusion with dBV.[23] The"v" comes from "volt", while "u" comes from"unloaded". dBu can be used regardless of impedance, but is derivedfrom a 600 Ω load dissipating 0 dBm (1 mW). Reference voltage In professional audio, equipment may becalibrated to indicate a "0" on the VUmeters some finite time after a signal has been applied at anamplitude of +4 dBu. Consumer equipment will more often use a much lower"nominal" signal level of -10 dBV.[24]Therefore, many devices offer dual voltage operation (with different gain or"trim" settings) for interoperability reasons. A switch or adjustmentthat covers at least the range between +4 dBu and -10 dBV is common inprofessional equipment. BmVdB(1mVRMS) – voltagerelative to 1 millivolt across 75 Ω.[25]Widely used in cable television networks, where thenominal strength of a single TV signal at the receiver terminals is about 0dBmV. Cable TV uses 75 Ω coaxial cable, so 0 dBmV corresponds to −78.75 dBW(−48.75 dBm) or ~13 nW. dBμV or dBuV dB(1μVRMS) – voltagerelative to 1 microvolt. Widely used in television and aerial amplifierspecifications. 60 dBμV = 0 dBmV. AcousticsProbably the most common usage of "decibels" inreference to sound loudness is dB SPL, sound pressure levelreferenced to the nominal threshold of human hearing: dB(SPL) dB (sound pressure level) – for sound in air andother gases, relative to 20 micropascals (μPa) = 2×10−5 Pa, thequietest sound a human can hear. This is roughly the sound of a mosquito flying3 meters away. This is often abbreviated to just "dB", which givessome the erroneous notion that "dB" is an absolute unit by itself.For sound in water and other liquids, areference pressure of 1 μPa is used. One Pascal is equal to 94 dB(SPL). This level isused to specify microphone sensitivity. For example, a typical microphone mayput out 20 mV at one pascal. For other sound pressure levels, the outputvoltage can be computed from this basis, except that noise and distortion willaffect the extreme levels. dB(PA) dB –relative to 1 Pa, often used in telecommunications. dB SIL dB sound intensity level – relative to 10−12W/m2, which is roughly the threshold of human hearing inair. dB SWL dB soundpower level – relative to 10−12 W. dB(A), dB(B), and dB(C) Thesesymbols are often used to denote the use of different weightingfilters, used to approximate the human ear's response to sound, although themeasurement is still in dB (SPL). These measurements usually refer to noise andnoisome effects on humans and animals, and are in widespread use in theindustry with regard to noise control issues, regulations and environmentalstandards. Other variations that may be seen are dBA or dBA.According to ANSI standards, the preferred usage is to write LA = xdB. Nevertheless, the units dBA and dB(A) are still commonly used as ashorthand for A-weighted measurements. Compare dBc, usedin telecommunications. dB HL or dB hearing level is used in audiograms as ameasure of hearing loss. The reference level varies with frequency according toa minimum audibility curve asdefined in ANSI and other standards, such that the resulting audiogram showsdeviation from what is regarded as 'normal' hearing. dB Q is sometimes used to denoteweighted noise level, commonly using the ITU-R 468 noise weighting. Audio electronics dBmdB(mW)– power relative to 1 milliwatt. No reference impedanceis assumed, although 600 ohms is common in audio equipment. dBFS dB(full scale) –the amplitude of asignal compared with the maximum which a device can handle before clippingoccurs. Full-scale may be defined as the power level of a full-scale sinusoid or alternativelya full-scale square wave. dBTP dB(truepeak) - peak amplitude of a signal comparedwith the maximum which a device can handle before clipping occurs.[28] Indigital systems, 0 dBTP would equal the highest level (number) the processor iscapable of representing. Measured values are always negative or zero, sincethey are less than or equal to full-scale. dBZ dB(Z)– energy of reflectivity (weather radar), related to the amount of transmittedpower returned to the radar receiver; the reference level for Z is 1 mm6m−3. Values above 15–20 dBZusually indicate falling precipitation. dBsm dBsm –decibel measure of the radar cross section (RCS) of a targetrelative one square meter. The power reflected by the target is proportional toits RCS. "Stealth" aircraft and insects have negative RCS measured indBsm, large flat plates or non-stealthy aircraft have positive values. Radio power, energy, andfield strength dBc dBc –relative to carrier—in telecommunications, thisindicates the relative levels of noise or sideband peak power, compared withthe carrier power. Compare dBC, used in acoustics. dBJdB(J)– energy relative to 1 joule. 1 joule = 1 watt per hertz, so power spectral density can be expressed indBJ. dBm dB(mW)– power relative to 1 milliwatt. When used in the radiofield, the dB is usually referenced to a 50 ohm load, with the resultantvoltage being 0.224 volts. There are times when spec sheets may show thevoltage & power level e.g. −120 dBm = 0.224 microvolts. dBμV/m or dBuV/m dB(μV/m)– electric field strength relative to 1 microvolt per meter.Often used to specify the signal strength from a television broadcast at areceiving site (the signal measured at the antenna output will be indBμV). dBf dB(fW)– power relative to 1 femtowatt.dBW dB(W)– power relative to 1 watt. dBk dB(kW)– power relative to 1 kilowatt. Antenna measurements dBi dB(isotropic)– the forward gain of an antenna compared with thehypothetical isotropic antenna, which uniformlydistributes energy in all directions. Linear polarization of the EM field isassumed unless noted otherwise. dBd dB(dipole)– the forward gain of an antenna compared with ahalf-wave dipole antenna. 0 dBd = 2.15 dBi dBiC dB(isotropiccircular) – the forward gain of an antenna compared to a circularly polarized isotropic antenna.There is no fixed conversion rule between dBiC and dBi, as it depends on thereceiving antenna and the field polarization. dBq dB(quarterwave)– the forward gain of an antenna compared to a quarter wavelength whip. Rarelyused, except in some marketing material. 0 dBq = −0.85 dBi Other measurementsdB-Hz dB(hertz) – bandwidth relativeto 1 Hz. E.g., 20 dB-Hz corresponds to a bandwidth of 100 Hz. Commonly used in linkbudget calculations. Also used in carrier-to-noise-densityratio (not to be confused with carrier-to-noise ratio, in dB). dBov or dBOdB(overload) –the amplitude of asignal (usually audio) compared with the maximum which a device can handle beforeclippingoccurs. Similar to dBFS, but also applicable to analog systems. dB(relative)– simply a relative difference from something else, which is made apparent incontext. The difference of a filter's response to nominal levels, for instance. dBrn dBabove reference noise. See also dBrnC. Dynamic MicrophonesDynamic microphones are versatile and ideal for general-purpose use. They use a simple design with few moving parts. They are relatively sturdy and resilient to rough handling. They are also better suited to handling high volume levels, such as from certain musical instruments or amplifiers. They have no internal amplifier and do not require batteries or external power.
  Analog mixers can be classed meaningfully by 2 variables. 1) The number of channels and 2) the number of busses. That's why you see most mixer have numbers in the model name, like a Mackie 32-8. That means 32 channels, 8 busses. Sometimes they add another 3rd number. Lets take a Behringer 2442 for example. That means 24 channels, 4 busses, 2 master outs. Unfortunately manufacturers don't always follow rigid definitions here and the numbers can be deceiving. Some "4 bus" mixers count the master outs as a bus, so its really a 2 bus+2 master outs. I will call those 2+2 bus mixers. Before you buy, check the specs and make sure the mixer is a "true" 4 bus if that is what you want. For the number of channels, some manufacturers count the effects returns as a channel and some don't. So a 16 channel mixer might only have 12 channels and two stereo effects returns. To add to the complexity, manufacturers are now adding USB and Firewire audio interfaces to their analog mixers. Remember what we said about "redundancy" a while back. You only need one audio interface in your rig and some of these may be very basic. Normally you connect an analog mixer to your existing audio interface. Confusing? Yes. That's why you need me. I will get your through this. In all cases, read specs and find out how many channels the board really has not counting the aux returns. Also find out how many busses the board has not counting of the Master outs. If it has an audio interface make sure you know exactly how many channels it can send and return from your DAW. To get information to make this page I went to manufacturers websites and dug the info out of product manuals. I suggest you do the same when you are ready to buy. Types of Analog Mixers for a Computer Recording Setup The Main question: How many tracks need to be recorded simultaneously (i.e., at the same time)? You need as many inputs on your soundcard or audio interface to cover that first off. Then you need that many independent outputs (sub outs) on your mixer to mate with these inputs. These independent outputs are called "sub outs" or the "alt 3-4 bus". These are different terms for the same thing. You can also use direct outs if the mixer has them, if you don't mind re-patching the gear you want to record into it's path. Types of Analog Mixers 1. 8 Bus (ideally for 8x8 audio interfaces, standalone multitrack recorders) 2. Analog Mixer with built in audio interface 3. 4 Bus (ideally for 4x4 audio interfaces) 4. 2+2 Bus (Ideally for 2x2 stereo soundcards) 5. Stereo Only (Ideal for those only connecting mics and guitars for tracking though workarounds are possible) 6. Rack Mixers 7. Preamp only (for those going mixerless on a budget) We'll talk about each one with examples to help you decide. 1. "8-bus" Mixers If you intend to record a full band in your studio, you need a board that can handle lots of mics and instruments simultaneously and let you listen to tracks already recorded. Remember the drum kit might take 4-5 mics itself. You'll probably need to send a monitor mix out one of the busses, have inserts on every channel for patching stuff in during mixdown, generous sends and returns. 8 bus mixers are a great way to go. Take a look at the Behringer SX4882 or the budget Behringer SX3282 Mackie 24-8 and 32-8 mixers. More upscale is the Soundcraft Ghost. If you are using a computer to record, pair that to an 8x8 audio interface, like a delta 1010, or a MOTU828mk2. You are also able to mix all 8 outputs coming from the audio interface on mixer faders.   High-definition video or HD video refers to any video system of higher resolution than standard-definition (SD) video, and most commonly involves display resolutions of 1,280×720 pixels (720p) or 1,920×1,080 pixels (1080i/1080p). This article discusses the general concepts of high-definition video, as opposed to its specific applications in television broadcast (HDTV), video recording formats (HDCAM, HDCAM-SR, DVCPRO HD, D5 HD, AVC-Intra, XDCAM HD, HDV and AVCHD), the optical disc delivery system Blu-ray Disc and the video tape format D-VHS.
[edit] Extra high-definition video modes
Common high-definition video modes Note: 1 Image is either a frame or, in case of interlaced scanning, two fields. (EVEN and ODD) Sound is a form of energy which Produes a sensation of hearing in our Ears. There are also other forms of Energy like;- Mechanical Energy Heat energy Light energy Prouction of Sound Take a tuning and set it vibration by striking its prong ona rubber pad. Bring it hear ur,s ear. Do you hear any sound. Touch one of the prongs of the vibration tuning fork with your frinds. Charateristics of a sound Wave. We can describe a sound wave by its. · Frequency · Amplitude and · Speed. Frequency tells us how ? Frequence an event occus:- Suppous you are beating a durm. How many times you are beating drum per unit times is called the frequency of your beating the drum. Propagation of Sound Sound is produced by vibrating objects. The matted or substance through which sound is transmitted is called amedium.It can be Solid , liquid or gas. Sound mmoves through a medium from the point of generation to the listener. Sound Need a medium to Travel Sound is a mechanical wave a needs a materials medium like air,water,Steel etc. For its propagation. It cannot travel through vacum. Which canbe demonstrated by the following experiment. Physics of sound The mechanical vibrations that can be interpreted as sound are able to travel through all forms of matter: gases, liquids, solids, and plasmas. The matter that supports the sound is called the medium. Sound cannot travel through a vacuum Noise Noise is a term often used to refer to an unwanted sound. In science and engineering, noise is an undesirable component that obscures a wanted signal Sound Mixers A sound mixer is a device which takes two or more audio signals, mixes them together and provides one or more output signals. The diagram on the right shows a simple mixer with six inputs and two outputs. As well as combining signals, mixers allow you to adjust levels, enhance sound with equalization and effects, create monitor feeds, record various mixes, etc. Overview · Channels o Inputs · Each input source comes into the mixer through a channel. The more channels a mixer has, the more sources it can accept. The following examples show some common ways to describe a mixer's compliment of channels:
· Input Channels· On most sound desks, input channels take up most of the space. All those rows of knobs are channels. Exactly what controls each channel has depends on the mixer but most mixers share common features. The list below details the controls available on a typical mixer channel. · Input Gain / Attenuation: The level of the signal as it enters the channel. In most cases this will be a pot (potentiometer) knob which adjusts the level. The idea is to adjust the levels of all input sources (which will be different depending on the type of source) to an ideal level for the mixer. There may also be a switch or pad which will increase or decrease the level by a set amount (e.g. mic/line switch). · Phantom Power: Turns phantom power on or off for the channel. · Equalization: Most mixers have at least two EQ controls (high and low frequencies). Good mixers have more advanced controls, in particular, parametric equalization. See also: Audio equalization. · Auxiliary Channels: Sometimes called aux channels for short, auxiliary channels are a way to send a "copy" of the channel signal somewhere else. There are many reasons to do this, most commonly to provide separate monitor feeds or to add effects (reverb etc). · Pan & Assignment: Each channel can be panned left or right on the master mix. Advanced mixers also allow the channel to be "assigned" in various ways, e.g. sent directly to the main mix or sent only to a particular subgroup. · Solo / Mute / PFL: These switches control how the channel is monitored. They do not affect the actual output of the channel. · Channel On / Off: Turns the entire channel on or off. o Slider: The level of the channel signal as it leaves the channel and heads to the next stage (subgroup or master mix How Dynamic Microphones Work As you may recall from your school science, when a magnet is moved near a coil of wire an electrical current is generated in the wire. Using this electromagnet principle, the dynamic microphone uses a wire coil and magnet to create the audio signal. The diaphragm is attached to the coil. When the diaphragm vibrates in response to incoming sound waves, the coil moves backwards and forwards past the magnet. This creates a current in the coil which is channeled from the microphone along wires. A common configuration is shown below.  Earlier we mentioned that loudspeakers perform the opposite function of microphones by converting electrical energy into sound waves. This is demonstrated perfectly in the dynamic microphone which is basically a loudspeaker in reverse. When you see a cross-section of a speaker you'll see the similarity with the diagram above. If fact, some intercom systems use the speaker as a microphone. You can also demonstrate this effect by plugging a microphone into the headphone output of your stereo, although we don't recommend it! The Electret Condenser Microphone  The electret condenser mic uses a special type of capacitor which has a permanent voltage built in during manufacture. This is somewhat like a permanent magnet, in that it doesn't require any external power for operation. However good electret condenser mics usually include a pre-amplifier which does still require power. Other than this difference, you can think of an electret condenser microphone as being the same as a normal condenserDirectional Properties Every microphone has a property known as directionality. This describes the microphone's sensitivity to sound from various directions. Some microphones pick up sound equally from all directions, others pick up sound only from one direction or a particular combination of directions. The types of directionality are divided into three main categories: 1. Omnidirectional Picks up sound evenly from all directions (omni means "all" or "every"). 2. Unidirectional Picks up sound predominantly from one direction. This includes cardioid and hypercardioid microphones (see below). 3. Bidirectional Picks up sound from two opposite directions. To help understand a the directional properties of a particular microphone, user manuals and promotional material often include a graphical representation of the microphone's directionality. This graph is called a polar pattern. Some typical examples are shown below.  Omnidirectional Captures sound equally from all directions. Uses: Capturing ambient noise; Situations where sound is coming from many directions; Situations where the mic position must remain fixed while the sound source is moving. Notes: · Although omnidirectional mics are very useful in the right situation, picking up sound from every direction is not usually what you need. Omni sound is very general and unfocused - if you are trying to capture sound from a particular subject or area it is likely to be overwhelmed by other noise. Cardioid Cardioid means "heart-shaped", which is the type of pick-up pattern these mics use. Sound is picked up mostly from the front, but to a lesser extent the sides as well. Uses: Emphasising sound from the direction the mic is pointed whilst leaving some latitude for mic movement and ambient noise. · The cardioid is a very versatile microphone, ideal for general use. Handheld mics are usually cardioid. Notes: There are many variations of the cardioid pattern (such as the hypercardioid below) Hypercardioid  Uses: Isolating the sound from a subject or direction when there is a lot of ambient noise; Picking up sound from a subject at a distance. Notes: By removing all the ambient noise, unidirectional sound can sometimes be a little unnatural. It may help to add a discreet audio bed from another mic (i.e. constant background noise at a low level).· You need to be careful to keep the sound consistent. If the mic doesn't stay pointed at the subject you will lose the audio. <!--[if !supportLists]-->· <!--[endif]-->Shotguns can have an area of increased sensitivity directly to the rear. Uses a figure-of-eight pattern and picks up sound equally from two opposite directions. Uses: As you can imagine, there aren't a lot of situations which require this polar pattern. One possibility would be an interview with two people facing each other (with the mic between them). Bidirectional This is exaggerated version of the cardioid pattern. It is very directional and eliminates most sound from the sides and rear. Due to the long thin design of hypercardioids, they are often referred to as shotgun microphones. |
Some microphones allow you to vary the directional characteristics by selecting omni, cardioid or shotgun patterns.
This feature is sometimes found on video camera microphones, with the idea that you can adjust the directionality to suit the angle of zoom, e.g. have a shotgun mic for long zooms. Some models can even automatically follow the lens zoom angle so the directionality changes from cardioid to shotgun as you zoom in.
Although this seems like a good idea (and can sometimes be handy), variable zoom microphones don't perform particularly well and they often make a noise while zooming. Using different mics will usually produce better results.
