2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
American engineers have developed a noise cancellation system that consists of a speaker and additional sensors around it. Due to the fact that the radio signal travels faster than sound, sensors have time to register the sound and transmit data to the speaker even before the sound reaches it. Thanks to this, the speaker has time to pick up the "opposite" sound that is in phase with the original. In the future, this circuit can be applied to headphones, say the engineers in an article presented at the SIGCOMM 2018 conference.
The principle of active noise canceling headphones is that they register the sound coming to them and create sound with the same frequency and amplitude, but in reverse phase, thereby suppressing the incoming sound. Despite the fact that the method itself allows you to 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 for the headphone microcontroller to register the sound and calculate the opposite wave. Because of this, the sound they emit is no longer completely opposite to the incoming sound, but lags behind it in phase.
Romit Roy Choudhury and his colleagues at the University of Illinois at Urbana-Champaign have created a system that allows audio devices to anticipate impending acoustic vibrations and calculate the “opposite” sound. The developers have implemented a prototype of the system in the form of a speaker, but they note that in the future this scheme can be applied to headphones as well. In addition to a speaker with a microphone, the system uses repeater sensors that record sound and send it to the speaker using a radio signal at a frequency of 900 megahertz.
Method diagram
The repeater can be located farther from the sound than the microphone in the speaker, so an algorithm created by the engineers analyzes all sound sources 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 blocks out high-frequency sound so that the headphones do not need to be equipped with sound-absorbing materials that would interfere with important sounds when the noise canceling system is turned off. In addition, since the system has a longer period of time to calculate the outgoing sound, more computationally demanding algorithms can be used for this.
Comparison of the new system with conventional active noise canceling headphones
The developers compared the performance of the system to commercially available active noise canceling headphones. During the experiment, they recorded the sound entering the ear of a mannequin, next to which was installed headphones or a speaker. It turned out that serial headphones can only suppress sounds with a frequency of up to about a thousand hertz, while the noise cancellation 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.
In 2015, Kickstarter launched a crowdfunding campaign to raise funds for headphones with active noise canceling, which can be configured from a smartphone. For example, according to the developers, headphones allow you to "turn off" specific sounds, such as a crying baby, the hubbub of the crowd or the noise of the subway.
