How does the brain recognize people by their voice?

Review expert: Yuan Xiandao, deputy chief physician of the Department of Otolaryngology, Beijing Anzhen Hospital, Capital Medical University

“Guess who I am?”

You must have played this game before. When a friend blindfolds you, you have to guess who blindfolded you by the sounds made by the people around you. So, how do you analyze your friend's voice?

Voice is one of the important features to identify each of us, and it also represents each of us as an individual. We can recognize relatives, friends and familiar people through voice, which is commonly known as "recognizing people by their voice".

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What is the principle of sound generation? Why can two people recognize each other through voice? Let's start with the generation of sound. Sound is generated by the vibration of objects, and human voice is the sound produced by the vibration of human vocal cords. Everyone has his or her own unique voice at every age, which is also one of his or her own symbols.

The three defining elements of sound are pitch, loudness, and timbre.

What determines the tone?

The pitch is determined by the frequency of the sound . Since the frequency of the sound source vibration is different, the pitch produced is also different.

For example, when playing a flute, harmonica, saxophone, or other musical instrument, you can produce different tones by pressing different holes while playing. This is because the air column vibrates at different frequencies.
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Sometimes people often say that girls have high-pitched voices and boys have rough voices. The essence of this is that most boys have a lower frequency when speaking, while most girls have a higher frequency. At the same time, boys' vocal cords are longer, wider, and thicker, while girls' vocal cords are shorter, thinner, and narrower, which leads to different tones.

Not only that, the reason why the voices of men and women are very different is also related to the way of vocalization. When boys speak, they mainly rely on the vibration of the throat and the resonance of the chest cavity. The sound effect will be relatively rough. The voice of girls relies on the vibration of the vocal cords and the resonance of the cranial cavity. The vocal cords on both sides contract, causing the airflow from the lungs and trachea to continuously impact the vocal cords, so the effect presented is more delicate.

What does loudness mean?

Loudness represents the intensity of sound , which is also known as the size of the sound. The stronger the vibration of the sound source, the stronger the sound.

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The loudness also has the meaning of identification. For example, some people speak more forcefully, the intensity of vocal cord vibration is greater, and the loudness of the voice is louder, which is what people call "loud voice". It is also a way to identify others by voice. At the same time, the loudness of people's voices can be controlled and adjusted according to their own wishes, that is, the volume of the voice can be controlled. For example, sometimes in certain places, people can deliberately speak in a low voice, but when they are far away, they need to raise the volume.

Therefore, the volume of the voice is mostly a personal habit, and people can control the loudness.

What does timbre represent? Tone is the characteristic of sound, which is mainly determined by the material and characteristics of the sound source. For example, the sounds produced by saxophone, clarinet, harmonica and flute are all different. People can feel the difference of each instrument at a glance, which is timbre.

Regardless of pitch and loudness, under the same loudness and pitch, we can still clearly find that the sounds produced by several instruments are quite different. Their structures and materials are different, which determines their different timbres. Due to the different structures of each person's vocal cords, most people have different timbres when speaking, and each person's timbre is also a representative of himself.

The underlying principles of sound generation

When people speak, the production of voice does not only rely on the throat, but is produced by the cooperation of multiple organs and systems.

The human vocal system can be simply divided into three parts: power organs, vibration organs, and resonance organs. The power organs are mainly the respiratory system and lungs, the vibration organs are the vocal cords, and the resonance organs are mainly the chest, oral cavity, nasal cavity, and throat. This is why people's voices are different from usual when they have a cold or a blocked nasal cavity, and their voices are hoarse when their throats are dry or painful.

The most important organ in the process of vocalization is the vocal cord , which is also the most important organ that determines the voice of each of us. The vocal cord is mainly composed of vocal muscles, and its function varies with the degree of contraction. The stronger the muscle contraction, the greater the elasticity.

The vocal cord muscles are covered by elastic cones, which are significantly thickened at the free edge of the vocal cords and are called vocal ligaments. The elastic cone fibers extend into the vocal cord muscles in many places and merge with the connective tissue between the muscle bundles. Therefore, the vocal cord muscles and elastic cones are tightly connected together, and the two structures move as one when vibrating.

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At the same time, the vocal cords will also change with age. From birth to around 20 years old, the vocal cords are constantly growing and developing, and the structure of the vocal cords is constantly improving and differentiating. That’s why people often say that children’s voices change as they grow up, and people’s voices are different at different ages. This is why the voices of children when they are young are called childish voices. Their vocal cords are not fully developed, and their voices are sweeter. After people are over 30, their vocal cords will continue to decay, the elasticity of the muscles in the vocal cords will continue to decrease, and the muscle fibers in the vocal cords will become thinner . This is why people become more and more powerless when they get older, and their timbre will also change to a certain extent compared to when they were young.

We can recognize each other through different voices mainly because different people have different timbre and pitch . Different genders, different ages and other factors will lead to different voices. We can distinguish the specific person by the difference in timbre and pitch. Although everyone can subjectively adjust their pitch and volume (loudness) when speaking, due to the uniqueness of each person's vocal cord structure, we can still rely on the uniqueness of each person's timbre to distinguish others.

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Men and women have different physiological structures and their vocal cords vibrate differently. In addition, the difference in resonance makes the voices of men and women very different when they speak. Except when using hormones or voice changers, most people can easily distinguish the gender of the speaker by voice.