Magic active noise reduction technology
Time:2022-04-12
Views:2151
When you take transportation every day, do you notice the noise pollution of the surrounding environment? Facing the annoying noise running in our ears, in addition to the passive method of blocking our ears, we can now take the initiative to eliminate the noise with sound.
The principle of active noise reduction is summarized in one sentence: phase cancellation is realized by emitting sound waves with the same frequency and amplitude as the noise phase.
If you want to understand this sentence, you must first understand what the sound is? What are the phase and amplitude? How interference occurs.
The sound we usually hear is actually the phenomenon that the air is squeezed and transmitted continuously.
When the air is squeezed, there will naturally be compressed and sparse parts. The two parts are staggered with each other, and the alternation is regarded as a cycle at a time, and how many cycles change in a second is called frequency. The sound we hear is often composed of many sounds with different frequencies. They are not only different in frequency, but also different in degree of compression / stretching, that is, different in amplitude and sound size.
The meaning of phase is also very simple. The position of sound wave in a period at a certain time is the phase. If we specify that the place where the air is compressed most is the zero point of the phase, then after half a cycle, where the air becomes the most sparse, the phase becomes 180 °. When the air is compressed most intensively again, the whole cycle passes, and the phase changes by 360 ° and becomes 0 ° again.
If we have two sounds with similar or the same frequency superimposed together to synthesize a sound, their amplitude will increase or decrease or remain unchanged. This phenomenon is called interference. If the two sounds have the same phase: I am the largest when you have the largest amplitude, and I am the smallest when you are the smallest, then the amplitude of the synthesized sound becomes larger and the sound changes. If the two sounds have the same frequency and amplitude, but the phase is opposite: the two
sound waves are opposite everywhere and offset each other, and the sound is eliminated.
Now active noise reduction headphones are selling well. How to realize this noise cancellation process?
If you want to generate sound waves to counteract noise, you must first get the information of noise. The active noise reduction headset is equipped with a feedback microphone to collect noise signals in the environment. There is a sequential problem here: collect the noise first, but the noise can be reduced only if the offset sound is generated at the same time with the noise. Therefore, the processor will predict the noise according to the noise, predict the noise at the next time, and generate corresponding offset sound waves.
In order to ensure the quality of noise reduction, a feedback microphone is also needed to detect whether the synthesized noise is really reduced. At this time, the processor will adjust the processing process according to the results measured by the feedback microphone, so as to further reduce the noise volume after synthesis. This is called adaptive process. For example, the processor becomes smarter and can continuously adjust itself according to the noise elimination effect to achieve the best noise reduction effect.
Finally, we should also know that there are many complex and delicate links in the specific implementation process, which is always the case from principle to reality. Now do you know active noise reduction technology?
The principle of active noise reduction is summarized in one sentence: phase cancellation is realized by emitting sound waves with the same frequency and amplitude as the noise phase.
If you want to understand this sentence, you must first understand what the sound is? What are the phase and amplitude? How interference occurs.
The sound we usually hear is actually the phenomenon that the air is squeezed and transmitted continuously.
When the air is squeezed, there will naturally be compressed and sparse parts. The two parts are staggered with each other, and the alternation is regarded as a cycle at a time, and how many cycles change in a second is called frequency. The sound we hear is often composed of many sounds with different frequencies. They are not only different in frequency, but also different in degree of compression / stretching, that is, different in amplitude and sound size.
The meaning of phase is also very simple. The position of sound wave in a period at a certain time is the phase. If we specify that the place where the air is compressed most is the zero point of the phase, then after half a cycle, where the air becomes the most sparse, the phase becomes 180 °. When the air is compressed most intensively again, the whole cycle passes, and the phase changes by 360 ° and becomes 0 ° again.
If we have two sounds with similar or the same frequency superimposed together to synthesize a sound, their amplitude will increase or decrease or remain unchanged. This phenomenon is called interference. If the two sounds have the same phase: I am the largest when you have the largest amplitude, and I am the smallest when you are the smallest, then the amplitude of the synthesized sound becomes larger and the sound changes. If the two sounds have the same frequency and amplitude, but the phase is opposite: the two
sound waves are opposite everywhere and offset each other, and the sound is eliminated.
Now active noise reduction headphones are selling well. How to realize this noise cancellation process?
If you want to generate sound waves to counteract noise, you must first get the information of noise. The active noise reduction headset is equipped with a feedback microphone to collect noise signals in the environment. There is a sequential problem here: collect the noise first, but the noise can be reduced only if the offset sound is generated at the same time with the noise. Therefore, the processor will predict the noise according to the noise, predict the noise at the next time, and generate corresponding offset sound waves.
In order to ensure the quality of noise reduction, a feedback microphone is also needed to detect whether the synthesized noise is really reduced. At this time, the processor will adjust the processing process according to the results measured by the feedback microphone, so as to further reduce the noise volume after synthesis. This is called adaptive process. For example, the processor becomes smarter and can continuously adjust itself according to the noise elimination effect to achieve the best noise reduction effect.
Finally, we should also know that there are many complex and delicate links in the specific implementation process, which is always the case from principle to reality. Now do you know active noise reduction technology?
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