Editing Binaural recording (section)

== Known issues ==

=== Averaging ===
The main focus of recording with a binaural head is to achieve a perfect binaural playback that is suited to all listeners. The problem arises that each human head has different shaped and sized features, making it very difficult to create a binaural effect compatible for everyone's ears. 

Averaging is done, either in the physical properties of binaural head microphones, or in the mathematical algorithm used to generate binaural sound using binaural panning software or ambisonic decoders. Some people may report hearing a very dramatic soundstage, while others may not. 

The effect that the shape of our head and our ears has on the sound we hear is part of what is called the [[Head-related transfer function|Head Related Transfer Function]], or HRTF.<ref name="Liitola 2006" /> Recent Apple [[iPhone Pro]]'s use the phone's camera and [[Lidar|LiDAR Scanner]] to create a 3D picture of the listener's ears, in order to create a [[Head-related transfer function|personalized HRTF]] file so that their own ear shape is factored into what they hear.

===Timbral issues===
In January 2012 BBC R&D worked together with [[BBC Radio 4]] to produce a binaural production of ''[[Private Peaceful]]''.<ref name="BBC Radio 4">{{Cite web |url=https://www.bbc.co.uk/blogs/radio4/2012/02 |title=BBC - Radio 4 and 4 Extra Blog |access-date=6 April 2017 }}</ref> The dramatization featured a reproduction of a 5.1 speaker system, and had 4 variations. At the start of each variation, the listener would hear a series of test signals allowing for a choice of which version gives them the best spatial experience. By doing this, BBC R&D have accepted that there will be variations on the success of the binaural reproduction, and therefore provided different mixes based on different sets of HRTF data. The release of ''Private Peaceful'' had an accompanying survey which all listeners were asked to complete. It asked questions about the success that the binaural reproduction had with the listeners and which version (1-4) the listener thought was most successful.

During an interview with Chris Pike from BBC R&D in September 2012, Pike stated that "you may get good spatial impression but timbral coloration is often an issue".{{Citation needed|date=March 2025}} The issue of timbral coloration is mentioned in a large amount of spatial enhancement research and is sometimes seen as the outcome of the misuse or insufficient amount of HRTF data when reproducing binaural audio for example, or the fact that the end-user simply will not respond well to the collected HRTF data. Francis Rumsey states in the 2011 article "Whose head is it anyway?"<ref name=":2">{{Cite journal |last=Rumsey |first=Francis |date=2011 |title=Whose Head Is It Anyway? Optimizing Binaural Audio |url=https://secure.aes.org/forum/pubs/journal/?elib=15982 |journal=Journal of the Audio Engineering Society |volume=59 }}</ref> that "badly implemented HRTFs can give rise to poor timbral quality, poor externalisation, and a host of other unwanted results".<ref name=":2" /> Getting the HRTF data correct is a key point in making the final product a success, and possibly by making the HRTF data as extensive as possible, there will be less room for error such as timbral issues. The HRTFs used for ''Private Peaceful''<ref name="BBC Radio 4" /> were designed by measuring impulse responses in a reverberant room, done so to capture a sense of space, but is not very external and there are obvious timbral issues as pointed out by Pike.{{Citation needed|date=March 2025}}

Juha Merimaa from [[Sennheiser]] Research Laboratories found that using HRTF filters to reduce timbral issues did not affect the spatial localization previously achieved using the data when tested on a panel of listeners.<ref>{{cite journal |last=Merimaa |first=Juha |date=2010 |title=Modification of HRTF Filters to Reduce Timbral Effects in Binaural Synthesis, Part 2: Individual HRTFs |url=http://www.aes.org/e-lib/browse.cfm?elib=15687 |journal=Journal of the Audio Engineering Society }}</ref> This explains that there are ways of reducing the effects of timbral issues on audio that have been processed with HRTF data, but this does mean further EQ manipulation of the audio. If this route is to be further explored, researchers will have to be happy with the fact that the audio is being manipulated in great amounts to achieve a greater sense of spatial awareness, and that this further manipulation will cause irreversible changes to the audio, something content creators may not be happy with. Consideration will have to be taken into how much manipulation is appropriate and to what extent, if any, will this affect the end users experience.

=== Issues related to headphone quality ===
Ideal listening conditions will most likely be experienced with headphones designed to give an as flat frequency response as possible in order to reduce colouration of the audio the user is listening to. But many people may only have access to low quality headphones, which can result in them hearing something very different from what was intended, and that can muddy the spatial cues in the binaural audio.

=== Loudspeaker compatibility ===
While a binaural recording can be played on a stereo loudspeaker system, the spatial cues that should only be heard by the left ear are heard by both ears, rather than only by the ear on the corresponding side, as would be the case with headphones. Likewise, with the right ear spatial cues. This means the spatial effect of the binaural sound is compromised to a degree, and in some cases can sound a little odd. It is possible to convert binaural sound into a format that sits more naturally on a stereo loudspeaker system using software, such as Logic Pro's [https://support.apple.com/en-gb/guide/logicpro/lgcef240d802/mac Binaural Post Processing plug-in].

[[File:Lautsprecherwiedergabe.svg|thumb|none|A method to convert binaural sound for loudspeaker playback]]