Binaural Audio

Drawbacks to typical stereo recording practices:
- Standard microphone recording formats lack binaural cues.
- Interaural time differences (ITD) are absent unless microphones are spaced like ears.
- Interaural amplitude differences (IAD) for high frequencies are missing due to microphone size.
- Pinna coloration is completely absent.
- Effects from the head and torso are missing.
Binaural audio’s limited popularity is due to its compatibility primarily with headphones.
Binaural technology is gaining commercial attention for:
- Creating 3D directional sound cues.
- Synthesizing accurate virtual environment acoustics using digital signal processors (DSP).
- Applications in flight simulators, computer games, virtual reality, and architectural auralization.
- Synthesizing ’loudspeakers’ in virtual home theatre systems.
  - Virtual Home Theater Video Player on Steam

People’s HRTFs are different (to varying degrees). However, some standard features make it difficult to generalize the HRTFs that should be used for commercial systems that serve many people.
Head movements that help to resolve directional confusion in natural listening are challenging to incorporate in reproduction situations.

Visual cues are often missing during binaural reproduction, and these usually have a substantial effect on perception.
Headphones differ in their equalization and method of mounting, leading to distortions in the perceived HRTFs on reproduction.
Distortions such as the signal chain’s phase and frequency response errors can affect the subtle cues required.

Oscar

Left to right trajectory around an artificial head, then front centre to above the head. Source: Cook 26

Music in 3 examples: Left track mono; Right track mono; binaural Check out the clarinet over your right shoulder!
Passing jet in 3 examples: Normal stereo; Low-bandwidth binaural; High-bandwidth binaural; Which gives the best impression of the jet being overhead? Source: Duda

The original chainsaw, heard first, was recorded in a stationary position, then using HRTF processing it appears to fly around you (try not to duck!) (Source: Pierce 39 & 40)
The footsteps are recorded moving in place, and then processed as if they were first in a dry, then a reverberant stairwell. Do the steps go up or down? Does your contextual knowledge of stairwells help the vertical localization?

Binaural microphones in modern times are often designed to be worn in the recordist’s ears, offering a less intrusive and more portable recording solution.
However, this design introduces challenges related to head movement on the part of the recordist and how it will be perceived by a listener whose head is assumed to be stationary.
There can be variations in how listeners perceive the sound image’s location outside the head due to the tradition of headphone listening, which tends to produce an in-head localization effect.
Two examples illustrate binaural recording applications:
1. A fireworks recording made using an artificial head demonstrates the use of binaural technology in capturing real-world events.
2. “Virtual Haircut” is a well-known and highly entertaining binaural audio drama showcasing immersive and spatial qualities of binaural audio recording techniques.