Why does the sound in the headset have a sense of direction?

When wearing headphones, we can often feel that the sound is obviously different from the front, back, left and right into our ears, so as to bring us a better auditory experience. Do you know how to do it?

Everyone knows that we can feel the loudness, tone and sound of the sound with one ears. However, if you want to distinguish the direction of the sound, you must rely on two ears. The reason is that the two ears can hear the time difference and the vocal difference. Time difference refers to the difference between the time when the sound reaches the two ears, and the difference between the sound level is the difference between the sound energy of the two ears. For example, when the sound source is on our right, our right ear will hear the sound first, and then the sound will reach the left ear.

Picture source: Google I/O

The sound from the front and the rear, at the same time to reach the ears, the sound energy is the same, so just rely on the two information of the time difference and the sound level difference. We cannot judge that the sound comes from the front or the rear.

So, the question is here again, how do you distinguish the front and back directions of the sound? In fact, the sound has been heard from sending to our ears, and has gone through three processes -the transmission process, physiological process, and psychological process. Because the physiological and psychological processes are almost unavailable, we only pay attention to the spread of communication here.

The transmission process is also called the physical process. It refers to the process that the sound waves from the sound source reach the auricle through the medium, and then pass through the ear canal to the tympanic membrane and cause their vibration. This is an extremely complicated process. Different from human auricle structure will make the waveforms formed by the influence of the sound waves.

Obviously, the transmission process in front of the sound source in front is different from the transmission process in the rear sound source! Because our ears are not symmetrical before and after. The sound from the front of the front can enter the ear canal directly through the auricle; the sound in front of the rear needs to go through the auricle to enter the ear canal. It is precisely because of this difference that we can distinguish between the source of the sound.

Picture source: Google I/O

The auricle is equivalent to a device that "encrypts" the sound, and after a long study of our brain, we have completely mastered this "decryption technology". Therefore, it can easily hear the front and rear positions of the sound source.

More scientifically, the crypto sound is not only the auricle, but also the body parts such as the head and the shoulders. Because the impact of this series is related to the head, this encryption method is also called: head -related functions.

The head -related function can be understood as the encryption method of our head for sound, which is aimed at different orientation. It is precisely because the head encryption in various directions is different, our brain can decrypt the direction of the sound.

In order to solve the encryption method of different sound source orientation, researchers can obtain head -related functions in different directions through measurement or calculation, and then form a database.

Image source: veer gallery

After we put on the headset, the sound was accepted by the head canal directly through the ear canal. Losing the process of head encryption, the sound inside the headset sounded no sense of direction.

However, with the development of sound signal processing technology, we can simulate the encryption process of the head by putting electronic devices inside the headset. If our electronic device is consistent with the encryption method of the head -related functions, the sound after the encryption of electronic equipment can be unlocked by the brain and successfully "deceived" 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 headset in a specific direction. In this way, the sound in the headset can sound a specific sense of direction. Produced: China Science Popularization Expo

Author: Wang Taihui's Key Laboratory of the Academy of Sciences of the Chinese Academy of Sciences of the Chinese Academy of Sciences

The China Science Popularization Expo is the Science Popular Science Platform of the Chinese Academy of Sciences. It is sponsored by the Computer Network Information Center of the Chinese Academy of Sciences. Relying on the high -end scientific resources of the Chinese Academy of Sciences, it is committed to spreading cutting -edge scientific knowledge and providing fun science and education services.

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