Noise Cancellation Headphones mechanism and process

Be relaxed, let them make noise

One man's noise is another man's music, but no matter what is your taste, ambient noise is the enemy. Luckily there is a piece of audio equipment design to enhance your listening experience keeping the ambient noise out and providing you with pure and perfect real beats and sweetness of music

We are talking about one of the common but ultimate equipment, NOISE CANCELLATION HEADPHONES. Treble of the pop song or bass of the jazz song, or even the soothing wave of Sufi songs, every music lover needs a tranquil and serene tone.
Let us take a look at mechanism of this superb equipment.

HISTORY

On a flight to Europe, Amar Bose, the founder of BOSE Corporation, put on a pair of airline supplied headphones, only to find that the roar of the jet engine prevented him from enjoying the audio. He started making calculation right there on the plan if it is possible to use headphones as a noise cancellation headphone a decade later.

WORKING PRINCIPLE

When we talk about wave, most of the people may think about water waves, like we see in pond or ocean. The shallow water wave is an example of transverse wave, which causes a disturbance in a medium perpendicular to a direction of the advancing wave. In the given illustration we can see crest, wavelength, amplitude and though. I will assume all of you must be familiar with these terms.

Sound wave have same characteristics as water waves but they are longitudinal wave created by a mechanical vibration in a medium that produces a series of compression and reflections  in a medium.
For sound wave, amplitude determines the intensity or loudness of the sound of the sound. Frequency determines the intensity or loudness of the sound. Frequency determines the pitch with higher pitch and lower frequencies producing a lower pitch notes. The brain is able to interpret these characteristics of sound, whwn detected by ear, our sense organ.

Noise-canceling headphones come in either active or passive types. Any type of headphone can provide some passive noise reduction,because the materials of the headphones themselves block out some sound waves, especially those at higher frequencies.The best passive noise-canceling headphones, however, are circum-aural types that are specially constructed to maximize noise-filtering properties. That means they are packed with layers of high-density foam or other sound-absorbing material, which makes them heavier than normal headphones. The trade off of all that extra weight is a reduction in noise of about 15 to 20 decibels (dB). But considering jet engines create 75 to 80 dB of noise inside the aircraft cabin, passive models have some serious limitations. That's where active noise-canceling headphones come in.

Active noise-canceling headphones can do everything that passive ones can do their very structure creates a barrier that blocks high-frequency sound waves. They also add an extra level of noise reduction by actively erasing lower-frequency sound waves. They actually create their own sound waves that mimic the incoming noise in every respect except one: the headphone's sound waves are 180 degrees out of phase with the intruding waves.

 Look at the illustration below, you can see how this works.

Notice that the two waves, the one coming from the noise-canceling headphone and the one associated with the ambient noise have the same amplitude and frequency, but their crests and troughs (compression and rarefaction) are arranged so that the crests (compression) of one wave line up with the troughs (rarefaction) of the other wave and vice versa. In essence, the two waves cancel each other out, a phenomenon known as destructive interference. The result: the listener can focus on the sounds he wants to hear.

Function of components

• Microphone - A microphone placed inside the ear cup "listens" to external sounds that cannot be blocked passively.

• Noise-canceling circuitry - Electronics, also placed in the ear cup, sense the input from the microphone and generate a "fingerprint" of the noise, noting the frequency and amplitude of the incoming wave. Then they create a new wave that is 180 degrees out of phase with the waves associated with the noise.

• Speaker - The "anti-sound" created by the noise-canceling circuitry is fed into the headphones' speakers along with the normal audio; the anti-sound erases the noise by destructive interference, but does not affect the desired sound waves in the normal audio.

• Battery - The term "active" refers to the fact that energy must be added to the system to produce the noise-canceling effect. The source of that energy is a rechargeable battery.

That means about 70 percent of ambient noise is effectively blocked, making noise-canceling headphones ideal for airline and train travel, open office environments or any other location with a high level of background noise

Pros of Using Noise-Cancelling Headphone 

 1. Noise-Cancelling Headphones Block Most Sounds

 2. Music Volume Does Not Need to Be High

 3. Lower Music Volumes Provides a Richer Listening Experience

 4. Noise-Canceling Headphones Are Great for Traveling

 5. Noise-Canceling Headphones Are Ideal for Studying

Cons of Using Noise-Cancelling Headphones

  1. Cost of Noise-Canceling Headphones

  2. High Power Usage of Noise-Canceling Headphones

  3. Quality of Sound When Using Noise-Canceling Headphones

  4. Not All Sounds Are Blocked by Noise-Canceling Headphones

  5. Comfort Concerns While Wearing Noise-Canceling Headphones

In spite of these tradeoffs, many people would never go back to normal audio headphones. That's because noise-canceling headphones do more than reduce noise. They also help alleviate fatigue when traveling, which can result from exposure to low-frequency noise for an extended period of time. You can even use noise-canceling headphones if you don't want to listen to another audio source but do want to cancel out background noise. And a little bit of quiet can be music to anyone's ears.

US President's ride is just a car or "tank"??

Ever wondered what may be special about 'The world's powerful persons' car??

We all are well aware about the safety measures taken for US President. Not even a bird dares to flock inside the security perimeter for him. Did you ever thought what must be inside his car, which make that particular piece 'a beast'. Have a look on some of the cool but hardcore features:-

 It's called "The Beast," but it might surprise you to learn that President Barack Obama's massive Cadillac isn't really a Cadillac. And there's not one, but a dozen, in the highly classified motor pool, each costing more than $1 million. The cars travel with their own mechanic, an armed federal agent who carries a vast arsenal of electronic diagnostic devices and tools.

We've come a long way since JFK's opentop Lincoln. Until only recently, the Secret Service bought the presidential limousines off the lot, then modified them with super-secret aftermarket products and systems. All that changed when George W. Bush became president. The reason? The stock presidential limos kept breaking down. All the extras the agency added to each vehicle created excess stress and weight beyond the real operational limits of the original cars. As a result, the transmissions often failed, “and the brakes would last about two trips,” said one veteran agent. “The cars were just too heavy, and they were a terror to drive, and even harder to stop.”

So the Secret Service decided to design and then build the car from the ground up. “The car may say Cadillac,” explained one agent, “but very little in that car is Cadillac.” Indeed, it is built by an R&D arm of General Motors in Detroit. But “even the Cadillac emblems on the hood and trunk are supersized. The car is really a truck that looks like a limo. And it drives like one, too.”

-- The fuel tank is armor-plated and encased in special foam to protect it from rupture in case of collision-or small-arms fire. And, perhaps not surprisingly, there's an onboard Halon fire-suppression system.

-- What's in the trunk? Extra weapons, a separate oxygen supply under the president's seat and emergency medical equipment, including bottles of the president's blood type in case the ambulance (one always travels in the motorcade) gets cut off.

-- The Beast is heavy: The armor plating (on five newer models) is so thick and the doors so heavy that it's nearly physically impossible for the president to open them from inside.

-- The interior is cut off from the outside world and sealed (in case of chemical attack). There's an encrypted satellite phone inside and a special interactive video system so the president can conduct secure video conferencing with officials in the Situation Room, embassies abroad or the Pentagon.

-- The car features military-grade armor (steel, aluminum, titanium and ceramic), surrounded by removable fiberglass sheets on the doors and fenders.

-- The Beast has special locking mechanisms, and communications and fire-suppression systems. It rides on special Kevlar-reinforced Goodyear run-flats.

-- The Secret Service has been experimenting with special night-vision cameras and monitors (the camera is mounted inside the grille) to be used in a doomsday scenario if, say, the windshield was somehow compromised or views were obstructed.

BY THE NUMBERS

3.7: Average miles to the gallon

12: Number of actual Beasts in service

$1.5 million: How much each Beast costs

18: How long the Beast is, in feet

8: Thickness, in inches, of the doors' armor plating

5: Thickness, in inches, of the windows–bulletproof, of course

15,000: Best guess on how much the Beast weighs, in pounds (the exact number is classified)

What doesn't it have? Sorry, 007 fans, but there are no rocket launchers, grenades or built-in weapons of any kind. No escape pod or ejection seat. Oh, and here's a mythbuster: The Beast is not diesel, but a gasoline V8. "Surprisingly," said one agent, "it has pretty good 0-60 pickup."

Bye bye wi-fi, Welcome Li-fi: Accessing data through lightbulbs

New research by Chinese researchers claimed to transmit data through 'Li-Fi' LED bulbs


Li-fi, a new invention in network and technology field. With the help of this concept, we will soon find our night bulb, street lamp post, vehicle light and other man-made light sources playing a vital role in connecting our network enabled device to high speed internet.

It is the another milestone after wi-fi technology. It was first coined by Professor Harald Hass from University of Edinburgh in UK at Global Talk on visible light communication.
The system uses a 1-watt LED bulb equipped with a signal modulation chip that encodes information as a series of light pulses that take place faster than we are capable of perceiving. With a specially-designed receiving station, the PCs were able to connect to the LED bulb. According to Chi Nan, a professor at Shanghai's Fudan University, ten Li-Fi kits will be on display next month at the China International Industry Fair, which begins on November 5.


Pros:-

• Wherever there is light, you get internet connectivity.
• In mobile devices, no separate network hardware will be used, its LED screen can be used as substitute
• Speed is expected to be near 4.7 GB/s.

Cons:-

• The energy utilization rate is only 5 percent.
• No light, no internet connectivity
• Costly and limited to high-end locations.

One glimmer of good news is that Li-Fi works even if the lights are dimmed to near-darkness. And the inability to pick up signals through buildings or walls could be a bonus for privacy-conscious web users. 

Now, days are not far when you will find people sitting under lamp post and downloading date faster than office and universities.

But with invention of this technology, a question arises"Do we really want to live in a world where household devices are connected to the 'net?"