Most people who have traveled with an MP3 player or other portable device have had the experience of intruding background noise ruining their listening experience. Noise canceling headphones can be a way of eliminating much of that interfering noise.
How do most headphones reduce noise?
Many headphones use a passive means of blocking out noise to keep it from reaching a listeners ears. Both the padding on around-the-ear headphones and the ear canal blocking aspect of earbud style earphones can reduce the amount of intrusion. Blocking noise passively is the primary means of reducing higher pitch sounds and very loud sounds such as explosions.
How do noise canceling headphones function differently?
Noise canceling headphones go a step further and actively block sound via a microphone placed near the ear to identify interfering background noise and a circuit which generates a new sound wave that cancels out the intruding sound wave from the background. This does not significantly increase the volume of sound reaching the listeners ear drum and thus does not increase the risk of damaging their hearing.
The active noise cancellation employed by noise canceling headphones works fairly well in eliminating low to mid range frequencies, but are less effective at blocking the sound of a human voice. In many instances, this is a positive attribute as it allows the wearer to hear those nearby who might need to interrupt. The intrusion of additional noise canceling sound waves generally has some effect on the overall music quality that the listener hears but at least for some of the better models the effect on sound quality is minimal.
What features will need to be considered when buying noise canceling headphones?
When choosing noise canceling headphones users need to determine which style, around-the-ear or earbud, they prefer to wear. Comfort is important and if a user is irritated with the sensation of an earbud in their ear for instance, around-the-ear or on-the-ear type headphones would be a better choice.
Like any product, the effectiveness of the various makes and models of noise canceling headphones varies significantly. Some report a 70% rate of effectiveness and others might be as high as 90%. Considering the technical specifications is important, but sometimes hearing is believing so while trying on the headphones to determine comfort, it is advisable to also compare effectiveness.
For most consumers, pricing is also a significant consideration. At the low end, some earbud headphones can come in around $20-$50, while at the high end spending around $350-$400 is also common.
For true audiophiles, those that travel in noisy environments, and those who find themselves fatigued by noisy crowded environments, noise canceling headphones can be a remedy worth considering.
Thursday, January 29, 2009
Electronics
Electronic is the study to understand the free flow of charges through number of devices and materials like inductors, resistors, semiconductors, nano-structures, capacitors and vacuum tubes. It is considered to be theoretical part of physics. The construction and designing of different electrical circuits is vital to solve the practical problems in the areas of computer engineering and electronic engineering.
Electrical components in an electronic system is physical entity that mainly affects the even minor electrons or any of its associated areas in the most efficient and desire manner to undertake some intended functions. Mathematical methods form vital part in the study of electronics. In order to become proficient enough in electrical engineering one also need to be proficient enough in the mathematics of circuit analysis.
Now-a-days electrical products that consists bulbs and tubes, cables, simulators, microwave, speakers, motor and engines, refrigerators, etc constitute great demand in the global market. Developing country like India has emerged out as an important electronic market. Indian electrical products are able to command great demand in the international market. However still there is a need to make huge investment in this field.
Source: electronics by webmaster
Electrical components in an electronic system is physical entity that mainly affects the even minor electrons or any of its associated areas in the most efficient and desire manner to undertake some intended functions. Mathematical methods form vital part in the study of electronics. In order to become proficient enough in electrical engineering one also need to be proficient enough in the mathematics of circuit analysis.
Now-a-days electrical products that consists bulbs and tubes, cables, simulators, microwave, speakers, motor and engines, refrigerators, etc constitute great demand in the global market. Developing country like India has emerged out as an important electronic market. Indian electrical products are able to command great demand in the international market. However still there is a need to make huge investment in this field.
Source: electronics by webmaster
Thursday, April 26, 2007
Multimedia Speakers
Computer speakers, or multimedia speakers, are external speakers and are usually equipped with a male 1/8 inch stereo jack plug (usually color-coded lime green per the PC 99 standard) for computer sound cards.
However, some have an RCA connector, and some people connect the output of their computer sound cards to a conventional stereo system.
There are also USB speakers which are powered from the 5 volts at a few milliamsp provided by the USB port, per the standard. Computer speakers are usually a simplified stereo system without a radio or other media sources built in.
Computer speakers range widely in quality and in price. Typically, the computer speakers packaged with computer systems are both small and simple. There are also advanced forms of computer speakers that have graphic equalization features (bass, treble, etc.) and sometimes built-in amplifiers.
It is common to connect active/powered computer speakers to a power strip. The power outlet should, as always, preferably be grounded for safety.
However, some have an RCA connector, and some people connect the output of their computer sound cards to a conventional stereo system.
There are also USB speakers which are powered from the 5 volts at a few milliamsp provided by the USB port, per the standard. Computer speakers are usually a simplified stereo system without a radio or other media sources built in.
Computer speakers range widely in quality and in price. Typically, the computer speakers packaged with computer systems are both small and simple. There are also advanced forms of computer speakers that have graphic equalization features (bass, treble, etc.) and sometimes built-in amplifiers.
It is common to connect active/powered computer speakers to a power strip. The power outlet should, as always, preferably be grounded for safety.
Thursday, February 8, 2007
Electric Heating
electric heater is an electrical appliance that converts electrical energy into heat. The heating element inside every electric heater is simply an electrical resistor, and works on the principle of Joule heating: an electric current flowing through a resistor converts electrical energy into heat energy.Domestic electrical underfloor heating:These systems are called radiant heating systems, regardless of whether they include a heat exchanger (also called a radiator) or are electrically powered.
When a home radiant heat system is turned on, current flows through a conductive heating material. For high-voltage radiant heat systems, line voltage (110 V or 230 V) current flows through the heating cable. For low-voltage systems, the line voltage is converted to low voltage (8 to 30 V) in the control unit (which contains a step-down transformer) and this low voltage is then applied to the heating element.
The heated material then heats the flooring until it reaches the right temperature set by the floor thermostat. The flooring then heats the adjacent air, which circulates, heating other objects in the room (tables, chairs, people) by convection. As it rises, the heated air will heat the room and all its contents up to the ceiling. This form of heating gives the most consistent room temperature from floor to ceiling compared to any other heating system.
When a home radiant heat system is turned on, current flows through a conductive heating material. For high-voltage radiant heat systems, line voltage (110 V or 230 V) current flows through the heating cable. For low-voltage systems, the line voltage is converted to low voltage (8 to 30 V) in the control unit (which contains a step-down transformer) and this low voltage is then applied to the heating element.
The heated material then heats the flooring until it reaches the right temperature set by the floor thermostat. The flooring then heats the adjacent air, which circulates, heating other objects in the room (tables, chairs, people) by convection. As it rises, the heated air will heat the room and all its contents up to the ceiling. This form of heating gives the most consistent room temperature from floor to ceiling compared to any other heating system.
Fixed Resistors
Some resistors are cylindrical, with the actual resistive material in the center (composition resistors, now obsolete) or on the surface of the cylinder (film) resistors, and a conducting metal lead projecting along the axis of the cylinder at each end(axial lead). There are carbon film and metal film resistors. The photo above right shows a row of common resistors. Power resistors come in larger packages designed to dissipate heat efficiently. At high power levels, resistors tend to be wire wound types.
Resistors used in computers and other devices are typically much smaller, often in surface-mount packages without wire leads. Resistors can also be built into integrated circuits as part of the fabrication process, using the semiconductor material as a resistor. But resistors made in this way are difficult to fabricate and may take up a lot of valuable chip area, so IC designers alternatively use a transistor-transistor or resistor-transistor configuration to simulate the resistor they require.
All wire except superconducting wire has some resistance, depending on its cross-sectional area and the conductivity of the material it is made of. Resistance wire has an accurately known resistance per unit length, and is used to make wire-wound resistors.
Resistors used in computers and other devices are typically much smaller, often in surface-mount packages without wire leads. Resistors can also be built into integrated circuits as part of the fabrication process, using the semiconductor material as a resistor. But resistors made in this way are difficult to fabricate and may take up a lot of valuable chip area, so IC designers alternatively use a transistor-transistor or resistor-transistor configuration to simulate the resistor they require.
All wire except superconducting wire has some resistance, depending on its cross-sectional area and the conductivity of the material it is made of. Resistance wire has an accurately known resistance per unit length, and is used to make wire-wound resistors.
Units of Resistor
The SI unit of electrical resistance is the ohm (Ω). A component has a resistance of 1 Ω if a voltage of 1 volt across the component results in a current of 1 ampere, or amp, which is equivalent to a flow of one coulomb of electrical charge (approximately 6.241506 × 1018 electrons) per second. The multiples kiloohm (1 kΩ = 1000 Ω) and megaohm (1 MΩ = 106 Ω) are also commonly used.
In an ideal resistor, the resistance remains constant regardless of the applied voltage or current through the device or the rate of change of the current. Whereas real resistors cannot attain this goal, they are designed to present little variation in electrical resistance when subjected to these changes, or to changing temperature and other environmental factors.
In an ideal resistor, the resistance remains constant regardless of the applied voltage or current through the device or the rate of change of the current. Whereas real resistors cannot attain this goal, they are designed to present little variation in electrical resistance when subjected to these changes, or to changing temperature and other environmental factors.
Resistor
A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohm's law. : The electrical resistance is equal to the voltage drop across the resistor divided by the current through the resistor. Resistors are used as part of electrical networks and electronic circuits.
A resistor is used to create a known voltage-to-current ratio in an electric circuit. If the current in a circuit is known, then a resistor can be used to create a known potential difference proportional to that current. Conversely, if the potential difference between two points in a circuit is known, a resistor can be used to create a known current proportional to that difference. Current-limiting.
By placing a resistor in series with another component, such as a light-emitting diode, the current through that component is reduced to a known safe value. A series resistor can be used for speed regulation of DC motors, such as used on locomotives and trainsets. An attenuator is a network of two or more resistors (a voltage divider) used to reduce the voltage of a signal.
A line terminator is a resistor at the end of a transmission line or daisy chain bus (such as in SCSI), designed to match impedance and hence minimize reflections of the signal. All resistors dissipate heat. This is the principle behind electric heaters. (See also electric heating and resistive heating)
A resistor is used to create a known voltage-to-current ratio in an electric circuit. If the current in a circuit is known, then a resistor can be used to create a known potential difference proportional to that current. Conversely, if the potential difference between two points in a circuit is known, a resistor can be used to create a known current proportional to that difference. Current-limiting.
By placing a resistor in series with another component, such as a light-emitting diode, the current through that component is reduced to a known safe value. A series resistor can be used for speed regulation of DC motors, such as used on locomotives and trainsets. An attenuator is a network of two or more resistors (a voltage divider) used to reduce the voltage of a signal.
A line terminator is a resistor at the end of a transmission line or daisy chain bus (such as in SCSI), designed to match impedance and hence minimize reflections of the signal. All resistors dissipate heat. This is the principle behind electric heaters. (See also electric heating and resistive heating)
Monday, January 8, 2007
Aspect Ratio Incompatibility
The television industry's changing of aspect ratios is not without difficulties, and can present a considerable problem.
Displaying a widescreen aspect (rectangular) image on a conventional aspect (square or 4:3) display can be shown:
1- in "letterbox" format, with black horizontal bars at the top and bottom
2- with part of the image being cropped, usually the extreme left and right of the image being cut off (or in "pan and scan", parts selected by an operator or a viewer)
3- with the image horizontally compressed
A conventional aspect (square or 4:3) image on a widescreen aspect (rectangular with longer horizon) display can be shown:
1- in "pillar box" format,
2- with black vertical bars to the left and right with upper and lower portions of the image cut off (or in "tilt and scan", parts selected by an operator)
3- with the image horizontally distorted
A common compromise is to shoot or create material at an aspect ratio of 14:9, and to lose some image at each side for 4:3 presentation, and some image at top and bottom for 16:9 presentation. In recent years, the cinematographic process known as Super 35 (championed by James Cameron) has been used to film a number of major movies such as Titanic, Legally Blonde, Austin Powers, and Crouching Tiger, Hidden Dragon.
This process results in a camera-negative which can then be used to create both wide-screen theatrical prints, and standard "full screen" releases for television/VHS/DVD which avoid the need for either "letterboxing" or the severe loss of information caused by conventional "pan-and-scan" cropping.
Displaying a widescreen aspect (rectangular) image on a conventional aspect (square or 4:3) display can be shown:
1- in "letterbox" format, with black horizontal bars at the top and bottom
2- with part of the image being cropped, usually the extreme left and right of the image being cut off (or in "pan and scan", parts selected by an operator or a viewer)
3- with the image horizontally compressed
A conventional aspect (square or 4:3) image on a widescreen aspect (rectangular with longer horizon) display can be shown:
1- in "pillar box" format,
2- with black vertical bars to the left and right with upper and lower portions of the image cut off (or in "tilt and scan", parts selected by an operator)
3- with the image horizontally distorted
A common compromise is to shoot or create material at an aspect ratio of 14:9, and to lose some image at each side for 4:3 presentation, and some image at top and bottom for 16:9 presentation. In recent years, the cinematographic process known as Super 35 (championed by James Cameron) has been used to film a number of major movies such as Titanic, Legally Blonde, Austin Powers, and Crouching Tiger, Hidden Dragon.
This process results in a camera-negative which can then be used to create both wide-screen theatrical prints, and standard "full screen" releases for television/VHS/DVD which avoid the need for either "letterboxing" or the severe loss of information caused by conventional "pan-and-scan" cropping.
Aspect Ratio
Aspect ratio refers to the ratio of the horizontal to vertical measurements of a television's picture. Mechanically scanned television as first demonstrated by John Logie Baird in 1926 used a 7:3 vertical aspect ratio, oriented for the head and shoulders of a single person in close-up.
Most of the early electronic TV systems from the mid-1930s onward shared the same aspect ratio of 4:3 which was chosen to match the Academy Ratio used in cinema films at the time.
This ratio was also square enough to be conveniently viewed on round cathode-ray tubes (CRTs), which were all that could be produced given the manufacturing technology of the time. (Today's CRT technology allows the manufacture of much wider tubes, and the flat-screen technologies which are becoming steadily more popular have no technical aspect ratio limitations at all.) The BBC's television service used a more squarish 5:4 ratio from 1936 to 3 April 1950, when it too switched to a 4:3 ratio. This did not present significant problems, as most sets at the time used round tubes which were easily adjusted to the 4:3 ratio when the transmissions changed.
In the 1950s, movie studios moved towards widescreen aspect ratios such as CinemaScope in an effort to distance their product from television. Although this was initially just a gimmick, widescreen is still the format of choice today and square aspect ratio movies are rare. Some people argue that widescreen is actually a disadvantage when showing objects that are tall instead of panoramic, others say that natural vision is more panoramic than tall, and therefore widescreen is easier on the eye.
The switch to digital television systems has been used as an opportunity to change the standard television picture format from the old ratio of 4:3 (1.33:1) to an aspect ratio of 16:9 (approximately 1.78:1). This enables TV to get closer to the aspect ratio of modern widescreen movies, which range from 1.66:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the most common of which uses what is called anamorphic widescreen format.
This format is very similar to the technique used to fit a widescreen movie frame inside a 1.33:1 35mm film frame. The image is compressed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PALPlus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no horizontal compression or expansion is used.
Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this may subside as the DVD playback software matures.
Furthermore, computer and laptop widescreen displays are in the 16:10 aspect ratio both physically in size and in pixel counts, and not in 16:9 of consumer televisions, leading to further complexity. This was a result of widescreen computer display engineers' uninformed assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls, subtitles or their Taskbar, as opposed to viewing content full-screen.
Most of the early electronic TV systems from the mid-1930s onward shared the same aspect ratio of 4:3 which was chosen to match the Academy Ratio used in cinema films at the time.
This ratio was also square enough to be conveniently viewed on round cathode-ray tubes (CRTs), which were all that could be produced given the manufacturing technology of the time. (Today's CRT technology allows the manufacture of much wider tubes, and the flat-screen technologies which are becoming steadily more popular have no technical aspect ratio limitations at all.) The BBC's television service used a more squarish 5:4 ratio from 1936 to 3 April 1950, when it too switched to a 4:3 ratio. This did not present significant problems, as most sets at the time used round tubes which were easily adjusted to the 4:3 ratio when the transmissions changed.
In the 1950s, movie studios moved towards widescreen aspect ratios such as CinemaScope in an effort to distance their product from television. Although this was initially just a gimmick, widescreen is still the format of choice today and square aspect ratio movies are rare. Some people argue that widescreen is actually a disadvantage when showing objects that are tall instead of panoramic, others say that natural vision is more panoramic than tall, and therefore widescreen is easier on the eye.
The switch to digital television systems has been used as an opportunity to change the standard television picture format from the old ratio of 4:3 (1.33:1) to an aspect ratio of 16:9 (approximately 1.78:1). This enables TV to get closer to the aspect ratio of modern widescreen movies, which range from 1.66:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the most common of which uses what is called anamorphic widescreen format.
This format is very similar to the technique used to fit a widescreen movie frame inside a 1.33:1 35mm film frame. The image is compressed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PALPlus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no horizontal compression or expansion is used.
Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this may subside as the DVD playback software matures.
Furthermore, computer and laptop widescreen displays are in the 16:10 aspect ratio both physically in size and in pixel counts, and not in 16:9 of consumer televisions, leading to further complexity. This was a result of widescreen computer display engineers' uninformed assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls, subtitles or their Taskbar, as opposed to viewing content full-screen.
Transmission Band
There are various bands on which televisions operate depending upon the country. The VHF and UHF signals in bands III to V are generally used. Lower frequencies do not have enough bandwidth available for television. Although the BBC initially used Band I VHF at 45 MHz, this frequency is no longer in use for this purpose. Band II is used for FM radio transmissions. Higher frequencies behave more like light and do not penetrate buildings or travel around obstructions well enough to be used in a conventional broadcast TV system, so they are generally only used for satellite broadcasting, which uses frequencies around 10 GHz. TV systems in most countries relay the video as an AM (amplitude-modulation) signal and the sound as a FM (frequency-modulation) signal. An exception is France, where the sound is AM.
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