Surround Sound Recording

Following on from my previous post about surround sound, it's one thing to listen and mix audio in 5.1 (or 7.1), but what about recording audio for exactly that? For this, I will be specifically talking about miking techniques for virtual reality as I am involved in an ongoing project to integrate audio into a VR system. The same VR game that I spoke about here; Mindful Escapes.

So by now we know that surround sound (in this case 5.1) is compiled of 5 full range speakers; front left, centre, front right, surround left surround right and a Low Frequency effect (LFE) (or sub-woofer). (Appendix A)

Appendix A - 5.1 speaker placement

Through research, I have come across some key miking techniques for VR audio.

IRT CROSS

The IRT Cross is essentially a double ORTF set-up (Appendix B) with a few slight differences, it is done using four cardioid mic's that are aligned in a perfect square; 90 degrees from each each other (Appendix C). There are slight differences between what would be a double ORTF and an IRT, one being that and ORTF set up has the mic's 110 degrees apart and the IRT being only 90 degrees (Bobby Owsinsky, 2019). Due to the angles being more acute on an IRT, the mic's must be further away in distance compared to an ORTF (IRT=20-15cm, ORTF=15-17cm) to eliminate any comb filtering that would occur in the overall recordings.

Appendix B - ORTF miking set up

Appendix C - IRT Cross

This technique is great for capturing acoustic ambience. In fact it is so efficient, the NPR used this exact miking technique for their radio expeditions from 1992-2007 (Radio expeditions, 2019). (Appendix D).

Appendix D - Mill Mcquay from NPR capturing ambience in a river, using an IRT Cross

This technique has stood out to me for the sole purpose that I am to record multiple soundscapes for Mindful Escapes. My partner and I, Tim Allison, have decided that the IRT cross will best suite as the recording technique we need to complete the project on time. There is currently 4 weeks until our audio assets are due and recording is to take place next week (week 7). I will continue this blog after the recording stage is complete and we are moving onto mixing our recordings.

References:

Bobby Owsinski's Music Production Blog. (2019). Bobby Owsinski's Music Production Blog. Retrieved 21 October 2019, from https://bobbyowsinskiblog.com/2016/07/27/4-surround-sound-miking-techniques/

Q. Does the centre of an image suffer with the ORTF recording technique?. (2019). Soundonsound.com. Retrieved 21 October 2019, from https://www.soundonsound.com/sound-advice/q-does-centre-image-suffer-ortf-recording-technique#targetText=The%20ORTF%20technique%20was%20developed,their%20capsules%20spaced%20by%20170mm.

Radio expeditions. (2019). Macaulaylibrary.org. Retrieved 21 October 2019, from https://www.macaulaylibrary.org/radio-expeditions/

NPR Choice page. (2019). Npr.org. Retrieved 21 October 2019, from https://www.npr.org/templates/story/story.php?storyId=4074610