1. Why a Recording Is Closer to the Voice Other People Hear
Have you ever been surprised when listening to a recording of your own voice on a smartphone? It is thought that other people hear a voice close to that recording. The voice you usually hear yourself contains both sound traveling through the air (air conduction) and sound traveling through the bones of your head (bone conduction). A recording only captures the sound traveling through the air [1].
It is explained that the bones of the head transmit low vibrations easily. When bone conduction is added, your own voice tends to sound lower and fuller. In recordings, this part is missing, so higher frequencies stand out [2]. However, this is a tendency, and the actual pitch of the voice does not change. In an experiment by Kimura and Yotsumoto (2018), the "filter" needed to adjust a recording to sound like one’s own voice varied greatly between people, and no setting suited everyone was found [1]. The discussion of air and bone conduction is handled in a separate note. Here, we follow the question: "Why do we still know it is our voice when we hear it?"
2. How the Stapedius Muscle in the Middle Ear Moves Before You Speak
Deep inside the ear, in the middle ear, there is the stapedius muscle, a very small muscle in the body. There are measurements investigating how this muscle moves when you speak [7]. In a 1975 report by Borg and colleagues, the human stapedius muscle was active when people produced their own voice. The electrical activity of the muscle often began before the voice came out, suggesting it is moved as part of the brain’s preparation for speaking [7].
This movement was shown to have the potential to reduce interference from low sounds, making it easier to hear outside speech. However, this measurement was performed on people with holes in their eardrums. It cannot be said that this applies to everyone.
3. How the Auditory Cortex Reacts Less to Your Own Voice While You Speak
The brain also plays a role. In the auditory cortex, the part of the brain that processes sound, your own voice seems to be treated specially. In a 2002 study by Houde and colleagues, they used a device that measures brain magnetic fields (MEG) to examine the auditory cortex’s reaction while speaking. The reaction was weaker while speaking than when listening to a recording of the same voice [5].
The researchers concluded that the auditory cortex lowers its sensitivity while speaking, adjusting its activity to match the expected way of hearing. The interpretation is that since sounds you produce yourself are predictable, there is no need to react strongly. This is similar to how tickling yourself does not feel ticklish. However, this is an analogy. This study examined the reaction of the auditory cortex, which is separate from the sensation of ticklishness.
4. Why the Brain's Reaction Stays Weak Even When Your Voice Is Shifted or Replaced by Another Voice
How precise is the brain’s prediction? What happens if your voice returns to you shifted? In a 2006 study by Heinks-Maldonado and colleagues, they compared the auditory cortex’s reaction (M100) when participants heard their own voice. The reaction was weakest when their own voice was heard as is. When the pitch was shifted, or when it was another person’s voice, the weakening was smaller [6].
This result suggests the brain may precisely distinguish between "sounds produced from inside" and "sounds coming from outside." However, what was observed was the strength of the brain’s reaction. It did not directly measure whether the person judged it as "my voice."
5. How Mice’ Brains Respond Less to Sounds They Make
The mechanism to hear self-produced sounds weakly may not be unique to humans. Mice naturally make sounds like footsteps when they move. In a 2018 study by Schneider and colleagues, when they repeated the experience of linking walking with artificial sounds, the influence from the brain area controlling movement to inhibitory neurons in the auditory cortex strengthened. As a result, the auditory cortex’s reaction to that sound was selectively weakened [8].
This suggests the brain can learn from experience to treat "sounds made when I move" like a filter. However, the sounds used were artificial sounds linked to walking, not voice itself. It cannot be stated definitively that this is the same mechanism as human voice.
6. How Familiarity, Mouth Movements, and Bone Conduction Help You Recognize Your Voice
Why can you recognize your own voice even though it sounds different? Let us add two studies to the previous discussions. Even when made hard to hear, your own voice is recognized. In a 2013 study by Xu and colleagues (with 30 Japanese participants), under difficult listening conditions that kept only high frequencies, one’s own voice was recognized more accurately than others’ voices [3]. The researchers considered that familiarity and the link to articulation movements might be involved [3].
Recognition improves when sound goes through bone. In conditions where voice was heard through bone conduction (a method of transmitting vibrations through bone), the discrimination between one’s own voice and others’ voices improved compared to conditions where sound traveled through air. On the other hand, the discrimination between familiar people’s voices and strangers’ voices did not improve [4]. It is not that bone conduction alone reveals your voice, but rather that discrimination improves.
7. An Experiment: Record "Good Morning" Three Times and Listen to Your Voice
Record "Good morning" three times on a smartphone and play it back. How does it differ from the voice you usually hear? Describe it with words you like, such as "low," "high," or "thin." Next, gently press both ears with your palms and say "Ahh." How does the way it sounds change when you cover your ears? Avoid putting fingers into the ear canal.
Another experiment: Immediately after listening to a recording, gently press both ears with your palms and say "Good morning." Comparing the recorded voice and the voice heard with ears pressed makes it easier to imagine that the proportion of sound going through bone changes. The story that "ear muscles move before speaking" starts with the 1975 measurements [7].