HRTF, hrtf modelization, 3D audio modelization, 3d audio, 3d sound labs

HRTF 101, the concept of binaural 3d audio implementation

The disruptive wave of Virtual Reality and 3D Audio enabled applications is coming. It is therefore important to understand how spatial audio works and what is behind the much talked about HRTF acronym as it is a foundational concept of any binaural 3D Audio implementation.

August 2, 2016, 15:31 – 3D Sound Labs

HRTF? What is it?

When a sound wave travels from a given location to our eardrums, it interacts with several parts of our body such as the head and the ears. All these reflections, diffraction and absorptions (depending mainly on the shape of our head and the structure of our outer ear) change the nature of the incoming sound, like a filter. These sound wave filters depend on the source’s direction. Our auditory system has learned over time to associate each specific filter to its direction. This is how we recognize where a sound comes from. The representation of these directional changes as filters is called “Head Related Transfer Function” or HRTF.
If you want to simulate a sound coming from a given direction, you just filter it with the HRTF of this direction, play it with headphones at the entrance of the ear canal and the auditory system will position the sound as coming from this direction since it recognizes the directional signature. This is the basic principle behind all the Virtual Reality Audio engines.

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HRTF are personal!

Since HRTF filters are based on our morphology and that we know that we are all different from each other with respect to our features… HRTF differs from one individual to another! If you use somebody else’s HRTF, you end up with inaccurate or fuzzy sound localization.

And because we are so different from each other (especially the shape of the ears which, like finger prints, is a biometric sign that uniquely identifies an individual!).

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Benefits of using personalized HRTF

Existing VR audio solutions do a somewhat good job at virtualizing 3D Audio with non-personalized HRTF. However, anybody who has experienced a VR Audio content with his own HRTF knows that the perception improvement compared to non-personalized HRTF is massive! With your own HRTF, everything sounds clear, sharp and incredibly real. You can really experience auditory presence in an audio scene. The best analogy we could think of is actual visual: listening to VR Audio with personalized HRTF is like watching video in UltraHD and listening with non-personalized HRTF is like watching a low Definition blurry video (see images below)
Besides providing audio immersion in Virtual Reality, personalized HRTF are also used in applications where good sound localization is mission critical. Precise localization of an enemy or an alarm by sound can be lifesaving and this is why many Military Research Facilities have laboratories where they measure HRTF for the Air Force personnel….


An Image based analogy

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World with Personalized HRTF (Analogy) / World with Standard HRTF (Analogy)


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