With the rapid development of science and technology, not only is there a convenient and fast lifestyle, but noise pollution is a problem that cannot be ignored in contemporary society. Although the country has issued a series of relevant standards and clear requirements for noise, all kinds of noise around daily life are still unavoidable - traffic noise from cars and airplanes, industrial noise from construction sites and equipment operation, and noisy and noisy life noise in streets and alleys......
The harm of noise to the human body can not be underestimated, in the continuous strong noise environment, it will not only affect people's sleep quality, but also damage people's hearing, and even cause damage to people's nervous system, such as dizziness, dizziness and other phenomena, and then produce some irreversible harm.
So people choose to use headphones to block out the noise. But regular headphones can only mask the noise by physically canceling or increasing the volume. As everyone knows, not only can you not listen to beautiful music, but also have a certain negative effect on your own hearing, at this time, the emergence of noise-canceling headphones is particularly important. However, in the face of such equipment, people will always have doubts, afraid that they are paying an IQ tax. Let's analyze it together!
Headphones that can effectively reduce external noise are called noise-canceling headphones, which are mainly divided into two categories according to the design principle, namely active noise cancellation and passive noise cancellation.
Passive noise-cancelling headphones
Passive noise-cancelling headphones are the most inexpensive noise-canceling technology to implement, and they are more common in everyday life, such as in-ear headphones that are tightly coupled to the human ear, and headphones that cover the human ear...... But whether it's in-ear or over-ear, ear tips are an important factor in their ability to passively cancel noise.
The noise cancellation principle of passive noise cancelling headphones is simple and crude, mainly through physical isolation or the use of the special structure of the headphones to absorb and block noise as much as possible. Because of this, high-density insulation materials are chosen in terms of material use, so the headphones will be slightly heavy, and wearing them for a long time will have a certain impact on comfort. And its limitations are larger, passive noise cancelling headphones are mainly aimed at high-frequency noise pollution, for noise pollution below 800Hz and lower frequency bands, if you want to achieve the best ideal effect, you will need to pay a higher cost, and at the same time, the noise reduction material inside the headphones will be heavier, and then lose its practical significance.
Active noise cancelling headphones
Active noise cancelling headphones can completely solve the problems of passive noise cancelling headphones, mainly to eliminate low-frequency and short-term noise pollution. Inside it is a system for noise cancellation......
The principle of active noise cancelling headphones is that the internal system collects and analyzes the noise, and then actively generates a sound with the same spectrum as the noise to be eliminated and the opposite phase through the built-in circuit processing, so that it can be superimposed with the noise in a specific space and eliminated.
At this stage, according to the working principle and design structure of active noise cancelling headphones, they can be divided into two types: feedback type and feed-forward type. Whether feed-forward or feedback-based ANC, headphones contain a microphone and a secondary sound source –
Microphones are responsible for collecting noise, and some composite ANC headphones will have two microphones, one to collect external noise, known as a reference microphone, and one to collect internal noise, known as an error microphone. According to the actual application scenario requirements of active noise cancelling headphones, the microphone should have the characteristics of small size, high sensitivity, and good frequency response.
Secondary sound sources mainly refer to various types of loudspeakers, which mainly convert electrical energy into sound and are able to radiate sound energy.
The external microphone of feed-forward ANC headphones usually faces outwards and collects external ambient noise through the earphones' acoustic holes. When the external microphone collects the noise signal and transmits it to the secondary sound source through the ANC control circuit, there is no feedback loop. However, it will have a good noise reduction effect for stable noise, but the application range will be greatly limited, and it is usually only found in low-end headphone products.
The internal microphone of feedback ANC headphones is located on the inside of the headphones, usually at the entrance to the ear canal. When the internal microphone collects the noise entering the headphones, it will generate a secondary sound signal with the same amplitude and equal frequency through the ANC noise reduction processing circuit, and finally transmit it to the secondary sound source, through which the noise of the opposite phase is released, and then the active noise cancellation operation is realized. The internal microphone of feedback active noise cancelling headphones is usually near the secondary sound source, which can more realistically reflect the noise felt near the hearing, so the noise reduction effect will be better, but the internal structure will be relatively complex.
Among many active noise cancelling headphone products, the relevant technical quality is an important factor to ensure the active noise cancellation effect, of course, in addition to quality, price and compatibility are also important issues that consumers need to consider.