Deep analysis of the principles, advantages and applications of bone conduction technology

Bone conduction may have been heard by many people. It is a way for sound to spread to the human ear. Many digital products, such as headphones, microphones and even mobile phones, can be applied to it. So what is the principle of bone conduction technology? What aspects of bone conduction can be used? What role does bone conduction technology play in the development of today's full-screen mobile phones? Today, Xiaobian one by one for your analysis.

Bone conduction is the use of the skull as a sound carrier

We know that the medium of sound transmission includes solid, liquid and air, and in general, the way sound waves are transmitted to the inner ear is air conduction and bone conduction (ie solid conduction). Air conduction is a well-known sound wave transmitted to the middle ear through the auricle and external auditory canal, and then transmitted to the inner ear through the ossicular chain. Bone conduction refers to the transmission of sound waves to the inner ear through vibrations such as the skull and jaw. Bone conduction is a very common physiological phenomenon. For example, when we hear the sound of chewing food, it is transmitted to the inner ear through the jaw.

Bone conduction is a very important way of hearing to remove air. People use this method to create many bone conduction hearing devices. At present, there are two main types of bone conduction hearing devices - electromagnetic and piezoelectric.

Electromagnetic bone conduction hearing device works well, but it is easy to cause damage to the user's body due to electromagnetic radiation. The piezoelectric bone conduction hearing device uses a piezoelectric vibrator (having a characteristic of generating mechanical vibration under the excitation of an electric signal) as a sounding element, which is less affected by electromagnetic radiation during wearing, and has the advantages of small volume, low power consumption, and the like.

No ear injury, no noise interference, etc. are advantages of bone conduction headphones compared to air conduction headphones. Why is this?

â–  First, because the bone conduction conveyor works close to the head of the human body, its main component bone vibrator is a purely mechanical vibrating component, and there is no potential radiation hazard of electromagnetic waves to the human brain.

â–  Second, because bone conduction does not require air as a medium, there is still a high degree of clarity in strong noise environments.

â–  Third, we know that wearing a normal earphone for a long time will cause irreversible loss of hearing, and bone conduction is not simply to increase the listening effect by volume amplification, so it will not damage the hearing.

â–  Fourth, it is very dangerous to wear ordinary headphones when walking, cycling or driving. The bone conduction listening mode does not occupy the ear canal. The user can hear the sound of the bone conduction while listening to the sound of the surrounding environment.

At present, in digital products, the use of bone conduction technology is mainly reflected in several types of products such as bone conduction microphones, bone conduction headphones, and bone conduction mobile phones.

The bone conduction microphone is a slight vibration of the head and neck bone caused by a person's speech to collect the sound signal and convert it into an electrical signal. Because it is different from the traditional microphone for collecting sound through air conduction, it can transmit high-definition sound in a very noisy environment. In many cases, such as fire scenes, firefighters with anti-virus can not speak directly into the microphone with their mouths, so bone conduction microphones can be used at this time.

Like the bone conduction microphone, the bone conduction earphone also transmits sound to the inner ear through the vibration of the skull. Because it is in contact with the bones, the sound can be heard clearly as usual when the ears are blocked, and the sound from the bone conduction earphone can be distinguished in a very noisy environment.

Although the application of bone conduction technology on mobile phones is not universal, as a tool to increase the proportion of screens, Sharp, Xiaomi and other manufacturers have already applied this technology, so that you can "listen" to the screen when using their mobile phones. The bone conduction speaker converts the communication signal into a vibration signal of the sound wave, drives the entire screen to vibrate, and transmits the sound to the user through the skull. Bone conduction technology is considered an effective way to increase screen ratio by avoiding the opening of the earpiece.

Of course, because bone conduction technology currently has certain technical shortcomings, the way to remove the earpiece from a full-screen mobile phone is not limited to the use of bone conduction. For example, the Xiaomi MIX, which is a full-screen mobile phone prologue, is used to simulate the cantilever beam piezoelectric ceramics and then conduct To the sound of the box in the middle of the phone, the image is to knock the edge of the bowl with chopsticks. We can hear the sound on the side of the bowl. This is also a kind of air-conducting sound.

Whether it is applied to a microphone, earphone or mobile phone, bone conduction technology is used in digital products. In fact, the application of bone conduction technology is far more than this. Bone conduction plays a more important role in helping hearing-impaired people, emergency rescue and fire fighting.

However, at present, the application of bone conduction technology in various fields is not very deep. This is because the bone conduction output volume is small, the frequency domain is narrow, the distortion is high, the low frequency attenuation is high, and the cost is high, which limits its further application. This is one of the reasons why the full screen mobile phone rarely uses the bone conduction technology. But technology is always improving and developing. In the future, bone conduction technology may become more mature and may be more widely used.