3D sound is self-descriptive, sound in three dimensions: Height (above/below), Depth (near/far), Around (360 degrees). It is how we naturally experience sound in real-life. A seagull crying overhead, a police siren zooming by your car, and voices at a party surrounding you. This is the common and literal definition. But, it doesn’t directly help us understand why 3D sound is a problem or what we can do about it.
So, let’s re-define 3D sound to focus on three meaningful elements: 1.) the sound source, 2.) room/environmental acoustics, and 3.) You. Our example du jour will be Mr. Seagull, a bird.
3D Sound In Real Life
The sound source itself has its own characteristics. In this case, Mr. Seagull makes a particular type of sound. He has a defined location, and may be moving somewhere.
After leaving Mr. Seagull, the sound propagates away and interacts with the environment, for the room/environmental acoustics. So, if Gull and you are at the beach, some sound arrives at you directly, but some also bounces off the sand and ocean before reaching you, much is just carried away into the vast open space. However, if you meet in the city, the sound might bounce off streets and buildings multiple times for a more reverberant sound.
Finally, You. Because of room/environmental acoustics, the sound that reaches you is actually coming from several directions and arriving at different times. Your brain is very sophisticated with all of this information. Without even thinking about it, you understand details about the sound source as well as the environment/room. How? Well, you have two ears, and each ear is receiving slightly different information because they are located at different points on your head. Your ear shapes are unique, and asymmetric – different from the front and back. So, you modify the sound that reaches your eardrums by having a unique anatomy and moving your head to interact with sounds and your environment.
Headphones/Earphones and You
Headphones are very problematic when it comes to 3D sound. For simplicity, think about a stereo music file: the left channel is only sent to the left ear, and the right channel is only sent to the right ear. All of the normal room-acoustic information, all the glorious reflections and sound interaction with your unique anatomy, are cut-off. Additionally, when you move your head, you no longer interact with the sound-field, but the sound stays fixed with you. Major sections of your sophisticated auditory system are bypassed.
The result is a fundamental lack of information for your brain to use in locating a sound in the environment around you. What remains is a small listening experience, where sound can only appear at the left ear, at the right ear, or, when the left and right are played simultaneously, the middle of the inside of your head.
Said another way, the characteristic sound of our friend Mr. Seagull, may be intact, he no longer exists in the real world. To use an optical analogy, if your headphones/earphones are good, it is like looking at a vivid photograph of a seagull, but this is not the same as seeing and interacting with the real thing.
This brings us to Virtual Reality. On the video side, we are no longer dealing with flat images. Virtual worlds are getting closer to real life with 3D renderings and stereoscopic imaging. You want to be transported with 3D video. However, the flat sound provided by headphones is problem. Your sophisticated audio system knows that sounds are not in the right location.
Can headphones rise to the level of VR video headsets? Can we put YOU back into 3D sound?
Yes. Tune in next time….
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