Listening to a recording of yourself can be disconcerting, often followed by the thought “is that what I sound like?” With more time being spent at home on remote conference calls, wondering why our voices sound different to us than to other people is increasingly poignant. Read on to learn more about this “heady” phenomenon.
To answer this question, we first need to discuss the ways in which sound propagates, which can be broken out into two categories:
- sound transmitted through compressible media (such as air or water).
- structure-borne sound.
Airborne sound transmission is exactly as it sounds (pun intended). The sound waves from the source travel through the air until they reach their destination or dissipate. Common examples of this are birds chirping, music heard through speakers or headphones, or the sound of your keyboard when typing an email. For strictly airborne sound transmission, the surface on which a source of sound rests does not factor into the perception of that sound at the receiver. For instance, consider a chirping bird: do its chirps sound different as the bird flies through the air compared to when the bird is perched on a tree branch? Except in some rather extreme cases, probably not.
Structure-borne sound transmission occurs when vibration enters an object and travels through it before being transduced into airborne sound. Structure-borne sound can explain why you can hear footsteps from the floor above you in buildings, how you can hear an approaching train well before you see it by pressing your ear against the rails, or why your phone vibrating sounds louder when it is sitting on a table instead of in your pocket. Sound transmitted through a solid material may sound different leaving the surface depending on the composition of the material and its dimensions.
When we speak, other people hear the propagation of our voices through the air, as do recording devices like microphones; however, we hear our own voices as both airborne and structure-borne sound via bone conduction. In addition to our ears hearing the airborne sound, vibrations from our vocal cords travel through our head to the inner ear. Our ears convert pressure waves in air to mechanical vibrations at the ear drum. These vibrations then propagate to three tiny bones in our middle ear, which then transfer acoustic energy from compression waves in air to fluid-membrane waves in the cochlea, which resides in the inner ear.
Our vocal cords vibrate the bones and tissue in our heads, which transmits directly to the cochlea, bypassing the middle ear. Because of its material properties, our skulls more efficiently transmit low-frequency vibrations resulting in a deeper sounding tone being relayed to our cochlea. The cochlea then sums this information and passes it to the brain via the auditory nerve. When we listen to a recording of our voices, that deeper part of our voice from bone conduction is missing, which makes our own voice sound foreign to us – higher pitched and “thinner” than we are used to.
So think twice before investing money into voice lessons. There are some things you just can’t change! But on the positive side – they say the camera adds 10 pounds. Isn’t it nice to know that it is taken away with your slimmer sounding voice?