Binaural Recording 2.0
The previous week we have talked about HRTF and how it relates to human hearing and perception of sound.
To clarify a few things:
“Binaural” doesn`t mean stereo, some claim the misconception started in the 50s; however there isn`t enough data to confirm for sure the reason behind it.
Stereo is sound reproduction which generates a phantom multi-directional perspective, for the technically correct term: True stereo means capturing or recording and reproduction of sound by stereographic dispersion to represent the position of recorded objects
Spreading an identical signal hard left and right doesn`t make it stereo, essentially it`s a mono channel although you can induce the illusion of stereo by altering or varying the amplitude of a signal ( more on stereo recording later)
Standard stereo or multi-mic recording techniques do not factor in the ear spacing.
One more thing to highlights is usually headphones are required for binaural reproduction.
Unlike loudspeakers; headphone design doesn`t introduce cross talk.
Cross-Talk is the leak from one channel to another which clutters stereo imaging and greatly reduces separation (more on this below)
Crosstalk measurement is usually implemented to calculate the amount being leaked across.
A weighting curve is recommended by IBA (Independent Broadcasting Authority) for use in the aforementioned measurement.
If you record a signal of two microphones positioned outwards with 6 inches in between, you wouldn`t be doing a real binaural recording.
The positioning and spacing indeed equate to that of an average human`s ear canal; however, this technique doesn`t factor in frequency adjustments and response resulting from ear/head shape.
A common technique is the use of two microphones positioned on either side of a dummy head to account for HRTFs.
Using a separating gobo has been a common simplified version for a binaural microphone configuration- not all cues are preserved for exact localization but it has worked well for reproduction on loudspeakers.
In Sound Design, A common technique known to designer called normalization.
Walter Murch created the concept in 1973
As Nick Peck said “The most convincing way to make something sound like it was recorded in a room is to record it in one”
Worldlizing means playing back a signal in the space in question and place a microphone to re-record it.
That means moving around with a high-quality mobile playback/recording rig.
It captures the sound with all the reverberant characteristics of the space. Although it takes time and effort, however, it`s most original and authentic
Binaural re-recording is capturing audio from multiple speakers through a pre-manufactured binaural microphone; in theory, you are capturing how your ears will hear multi-channel content.
Next, we will explore common microphones and techniques in binaural, I will also include common practices and known issues.