Noise cancelling headphones are as popular as ever, but have we really asked ourselves where did all this hype come from? Let’s take a moment and go back in time to discover the geniuses behind this innovative noise cancellation idea.
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Brace yourself, I’m gonna talk history to you now.
It all started in Germany in 1933 when Paul Lueg, a doctor of philosophy and medicine, submitted a patent application about using phase-advancing waves to cancel sinusoidal tones in ducts and inverting polarity to cancel sounds around a loudspeaker.
Sounds complicated, but actually the process incorporated displacing the phases with the source of sound oscillations (i.e. in simpler terms vibration of air particles parallel to the direction of wave) in a way that their superposition (i.e. superposition property, according to which net response by two or more stimuli in the response sum is caused by each stimulus individually for all linear systems) is in mechanical manner.
Let’s stop with the science here and continue with the patent, which was granted in 1936. It was theoretically functional, however there wasn’t any proper equipment to detect, process and generate sound. Paul Lueg couldn’t implement this to a further phase.
Later in 1950s, Dr. Lawrence Jerome Fogel took over and he was one of the pioneers in evolutionary computation and human factors analysis research. Fogel developed systems and submitted patents on active noise cancellation in the field of aviation (helicopters to be exact).
This system was designed to reduce noise for the pilot in the cockpit area and help make the communication easier. Fogel was considered to be the inventor of active noise cancellation and he created one of the first noise cancelling headphones systems.
Around the same time the Air Force Research Laboratory (AFRL) had an acoustics research program that was focusing on hearing conservation and protection, communicating speech, measuring noise and community noise modeling. While working on active and passive hearing protection technologies, AFRL also had an ANR headset project in between 1956 and 1957.
Willard Meeker was the leader of the project and introduced the concept of earmuffs and earplugs as passive hearing protectors which was later developed by Dr. Charles Nixon. These passive hearing protectors were enhanced with Meeker’s newly designed active noise control model.
The circumaural earmuffs had 50-500 Hz bandwidth and 20 dB maximum attenuation. This was a breakthrough invention for noise cancelling headphones at the time which laid a ground for further developments.
Here comes the most prominent part in the story of noise cancelling headphones
Fastforwarding to 1978, a sound engineer and the founder of Bose Corporation Dr. Amar Bose first thought about reducing noise in headphones during his flight to Europe.
Listening to music and relaxing wasn’t an option for him because of airplane engine noise, so he dedicated his time to the concept of building noise cancelling headphones that started right in that plane.
By the time his trip was over, he gathered together a whole research team for building the noise reduction technology.
The end result was that BOSE came up with a whole new working prototype of acoustic noise cancelling headphones. This buddy was enhanced with a built-in microphone in each earmuff, which detect the external sound sooner than it reaches the human ears.
Then, noise-canceling circuitry (which is also in the earmuff) detects the microphone input and measures the frequency and amplitude of the soundwave to create an opposing soundwave.
Later the two sound waves are combined together along with destructive interference signal and the anti-sound removes the noise without affecting the normal sound.
This was the ultimate time when Bose headphones passed a real test in 1986 by Dick Rutan and Jeana Yeager. They flew a two-seater plane (known as Rutan Model 76 Voyager) for 9 days, 3 minutes and 44 seconds which set a new flight endurance record. Imagine how difficult would it be to fly in the air for that long without noise cancelling headphones!
Either way, Bose wasn’t the only headphone producing company to work on noise cancelling headphones. Another major Germany-based headphone producing company called Sennheiser worked on active noise reduction in headphones.
They were designed to help pilots of the largest German airline Lufthansa protect themselves from low-frequency noises. They presented the first certified (FAA-TSO) active noise cancelling pilot headset by the name of LHM 45 NoiseGard in 1987.
From then on, noise cancelling headphones gained fame and caught the eye of many headphone and other audio equipment producing companies. People started using them not only in aviation but in their daily routine as well since they’re completely safe for ears.
Noise cancelling headphones are also quite widely used by business folks to have better conference calls.
The market has become fairly competitive, and if you’re also in search of the best noise cancelling headphones, we got your back! By the way, they do not have a negative impact on your hearing.
In case you are interested in noise cancellation, we have designed an AI noise reduction app called Krisp that will remove noise in your conference calls.
The technology works in a way that will help you cancel both your noise and the noise coming from the other call participants. Now that’s something noise cancelling headphones wouldn’t be able to do, so get it while you can. 😉
Let’s see how this never-ending story of noise cancelling headphones will change in 2019 and where it will take us!
"Sound suppression" redirects here. For a muzzle device for a gun, see Silencer (firearms) . For deflecting noise in rocket launches, see Sound suppression system
Graphical depiction of active noise reductionActive noise control (ANC), also known as noise cancellation (NC), or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in commercial airline headsets with the technology becoming available in the late 1980s. The technology is also used in road vehicles, mobile telephones, earbuds, and headphones.
Explanation
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Sound is a pressure wave, which consists of alternating periods of compression and rarefaction. A noise-cancellation speaker emits a sound wave with the same amplitude but with inverted phase (also known as antiphase) relative to the original sound. The waves combine to form a new wave, in a process called interference, and effectively cancel each other out – an effect which is called destructive interference.
Modern active noise control is generally achieved through the use of analog circuits or digital signal processing. Adaptive algorithms are designed to analyze the waveform of the background aural or nonaural noise, then based on the specific algorithm generate a signal that will either phase shift or invert the polarity of the original signal. This inverted signal (in antiphase) is then amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform, creating destructive interference. This effectively reduces the volume of the perceivable noise.
A noise-cancellation speaker may be co-located with the sound source to be attenuated. In this case it must have the same audio power level as the source of the unwanted sound in order to cancel the noise. Alternatively, the transducer emitting the cancellation signal may be located at the location where sound attenuation is wanted (e.g. the user's ear). This requires a much lower power level for cancellation but is effective only for a single user. Noise cancellation at other locations is more difficult as the three-dimensional wavefronts of the unwanted sound and the cancellation signal could match and create alternating zones of constructive and destructive interference, reducing noise in some spots while doubling noise in others. In small enclosed spaces (e.g. the passenger compartment of a car) global noise reduction can be achieved via multiple speakers and feedback microphones, and measurement of the modal responses of the enclosure.
Applications
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Applications can be "1-dimensional" or 3-dimensional, depending on the type of zone to protect. Periodic sounds, even complex ones, are easier to cancel than random sounds due to the repetition in the wave form.
Protection of a "1-dimension zone" is easier and requires only one or two microphones and speakers to be effective. Several commercial applications have been successful: noise-cancelling headphones, active mufflers, anti-snoring devices, vocal or center channel extraction for karaoke machines, and the control of noise in air conditioning ducts. The term "1-dimension" refers to a simple pistonic relationship between the noise and the active speaker (mechanical noise reduction) or between the active speaker and the listener (headphones).
Protection of a 3-dimension zone requires many microphones and speakers, making it more expensive. Noise reduction is more easily achieved with a single listener remaining stationary but if there are multiple listeners or if the single listener turns their head or moves throughout the space then the noise reduction challenge is made much more difficult. High frequency waves are difficult to reduce in three dimensions due to their relatively short audio wavelength in air. The wavelength in air of sinusoidal noise at approximately 800 Hz is double the distance of the average person's left ear to the right ear;[1] such a noise coming directly from the front will be easily reduced by an active system but coming from the side will tend to cancel at one ear while being reinforced at the other, making the noise louder, not softer.[a] High frequency sounds above 1000 Hz tend to cancel and reinforce unpredictably from many directions. In sum, the most effective noise reduction in three-dimensional space involves low frequency sounds. Commercial applications of 3-D noise reduction include the protection of aircraft cabins and car interiors, but in these situations, protection is mainly limited to the cancellation of repetitive (or periodic) noise such as engine-, propeller- or rotor-induced noise. This is because an engine's cyclic nature makes analysis and the noise cancellation easier to apply.
Modern mobile phones use a multi-microphone design to cancel out ambient noise from the speech signal. Sound is captured from the microphone(s) furthest from the mouth [noise signal(s)] and from one closest to the mouth [desired signal]. The signals are processed to cancel the noise from the desired signal, producing improved voice sound quality.[citation needed]
In some cases, noise can be controlled by employing active vibration control. This approach is appropriate when vibration of a structure produces unwanted noise by coupling the vibration into the surrounding air or water.
Active vs. passive noise control
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Noise control is an active or passive means of reducing sound emissions, often for personal comfort, environmental considerations or legal compliance. Active noise control is sound reduction using a power source. Passive noise control is sound reduction by noise-isolating materials such as insulation, sound-absorbing tiles, or a muffler rather than a power source.
Active noise cancelling is best suited for low frequencies. For higher frequencies, the spacing requirements for free space and zone of silence techniques become prohibitive. In acoustic cavity and duct based systems, the number of nodes grows rapidly with increasing frequency, which quickly makes active noise control techniques unmanageable. Passive treatments become more effective at higher frequencies and often provide an adequate solution without the need for active control.[2]
History
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Electronic noise management test in Vienna, 1973The first patent for a noise control system—U.S. patent 2,043,416—was granted to inventor Paul Lueg in 1936. The patent described how to cancel sinusoidal tones in ducts by phase-advancing the wave and cancelling arbitrary sounds in the region around a loudspeaker by inverting the polarity.[3] In the 1950s Lawrence J. Fogel patented systems to cancel the noise in helicopter and airplane cockpits. In 1957 Willard Meeker developed a working model of active noise control applied to a circumaural earmuff. This headset had an active attenuation bandwidth of approximately 50–500 Hz, with a maximum attenuation of approximately 20 dB.[3] By the late 1980s the first commercially available active noise reduction headsets became available. They could be powered by NiCad batteries or directly from the aircraft power system.
See also
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Notes
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The average head is about 21.5 cm (8.5 in) from ear to ear. Assuming the speed of sound is 343 meters per second (1125 feet per second), the full wavelength of a tone of 1600 Hz reaches from ear to ear. A tone of half that frequency, 800 Hz, has a wavelength twice as long. A single such tone coming from the side will appear at the two ears 180 degrees out of phase—one ear compared to the other. An active noise control tone coming from a different angle will not be able to attenuate the original tone in both ears at once.
References
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