Why does the sound in the wireless bluetooth earphones have a sense of direction?
When wearing wireless bluetooth earphones, we often feel that the sound is transmitted into our ears from the left and right sides, which brings us a better listening experience.
We need to know that from the time when the sound in the wireless bluetooth earphones is emitted to being heard by our ears, there are three processes-the transmission process, the physiological process and the psychological process. Since the physiological and psychological processes are almost uncontrollable, here we only focus on the communication process.
Obviously, the propagation process of the sound source in the wireless bluetooth earphones directly in front is different from the propagation process of the sound source in the wireless bluetooth earphones directly behind! Because our ears are not symmetrical. The sound in the wireless bluetooth earphones from the front is reflected by the auricle and can directly enter the ear canal; while the sound from the back needs to bypass the auricle to enter the ear canal. It is precisely because of this difference that we can distinguish the front and back of the sound source in the wireless bluetooth earphones .
The auricle is equivalent to a device that "encrypts" the sound in the wireless bluetooth earphones , and our brain has fully mastered this "decryption technology" after a long time of study, so it can easily hear the front and back directions of the sound source in the wireless bluetooth earphones . Now, we finally have the answer. The direction of the sound source in the three-dimensional space of binaural positioning depends on the "encryption" of the auricle.
In order to decrypt the encryption methods of different sound source positions, researchers can obtain head correlation functions in different directions through measurement or calculation, and then compose a database.
After we put on the wireless bluetooth earphones , the sound passes directly through the ear canal and is received by the tympanic membrane. Without the process of head encryption, the sound in the wireless bluetooth earphones will not sound directional.
However, with the development of acoustic signal processing technology, we can simulate the encryption process of the head by inserting electronic equipment inside the wireless bluetooth earphones. If the encryption method of our electronic device is consistent with that of the head-related function, then the sound encrypted by the electronic device can be decrypted by the brain to obtain the location information, successfully "deceiving" the brain.
It is based on this idea that engineers have developed a spatial audio method based on the head-related function database. They use digital circuits to simulate the entire head-related function database, and then encrypt the sound in the wireless bluetooth earphones in a specific direction, so that the sound in the wireless bluetooth earphones can sound with a specific sense of direction.
Since this kind of sound is not emitted from the real space, but is "encrypted" through a virtual way of signal processing, it is called virtual surround sound.
In recent years, with more and more applications of wearable devices such as earphones, virtual surround sound technology has been widely used, and it is also called immersive spatial audio technology by technology companies.