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DateDate: 28-08-2018, 07:49

American engineers have developed a noise reduction system that consists of a speaker and additional sensors around it. Due to the fact that the radio signal spreads faster than the sound, the sensors manage to register the sound and transmit the data to the speaker before the sound reaches it. Thanks to this, the speaker manages to pick up the "opposite" sound, which coincides with the original one in phase. In the future, this scheme can be used for headphones.
This is stated in the article on the results of the SIGCOMM 2018 conference.
The principle of operation of headphones with active noise cancellation is that they record the sound coming to them and create a sound with the same frequency and amplitude, but the reverse phase, so that the incoming sound is suppressed. Despite the fact that the method itself can effectively suppress ambient sounds, real devices do not always cope with this task, especially with acoustic vibrations with a frequency of more than a thousand hertz. The fact is that it takes some time to register the sound and calculate the opposite wave from the microcontroller of the headphones. Because of this, the sound emitted by them is no longer completely opposed to the incoming sound, but lags behind it in phase.
Romit Roy Choudhury (Romit Roy Choudhury) and his colleagues from the University of Illinois at Urbana-Champaign have created a system that allows audio devices to know in advance about the approaching acoustic vibrations and to calculate the "opposite" sound. The developers have implemented a prototype system in the form of dynamics, but they note that in the future this scheme can be applied to headphones. In addition to the speaker with a microphone, the system uses transponder sensors that record audio and transmit it to the speaker using a radio signal at a frequency of 900 megahertz.
The repeater can be farther from the sound than the microphone in the speaker, so the algorithm created by the engineers analyzes all the sources of sound and determines the closest to the sound. In the same way, the algorithm can select a specific repeater if several devices are used in the system at once.
One of the advantages of this system is that it allows you to block high-frequency sound, so that the headphones can not be equipped with sound-absorbing materials that interfere with hearing important sounds when the noise-canceling system is turned off. In addition, since the system has a longer time interval for calculating the outgoing sound, more sophisticated algorithms can be applied to this.
The developers compared the effectiveness of the system with commercially available headphones with active noise reduction. During the experiment, they recorded the sound entering the ear of the dummy, next to which were installed headphones or a speaker. It turned out that the serial headphones can only suppress sounds with a frequency of up to about a thousand hertz, while the noise reduction of the new system works for sounds with a frequency of up to four kilohertz. In addition, even at frequencies up to one kilohertz, the suppression of the new system exceeds the suppression of the tested headphones by an average of 6.7 decibels.