Something similar happens with movies. We can watch an old film with a mono soundtrack and get totally into it. But if a stereo sound suddenly appears in the middle of an otherwise mono movie, it will probably jolt us a bit unless there is a reason for the change that the film makes clear.
I think that the aesthetics of a sound, its basic storytelling power, should always be the main factor we consider as sound recordists, editors, designers, and mixers. If I am working on a film, and I have a choice between using a powerful and evocative mono sound effect or a mediocre sound effect that is stereo or multi-channel, I will always choose the mono sound, then find a way to use it that doesn’t draw attention to the fact that it’s a mono sound in a sea of stereo or 7.1.
The film “Apocalypse Now,” which I worked on, has an immersive multi-channel track that still stands up well today, though it contains many mono sound effects. When Walter Murch was mixing the effects for the film, he used several techniques to disguise the mono sounds and make them blend in. One strategy is to dynamically pan the mono sound. Another is to add stereo or multi-channel reverb or delay to it. These days we have lots of “stereoizer” plugins as well. But surprisingly, in many storytelling contexts we won’t need to enhance a mono sound. It can sit, unmoving, in a multichannel environment doing its job and not jolt us at all by being mono. A stereo sound can sometimes be distracting too, by the way.
I suggest using Ambisonic or other multichannel sound effects recordings when they work well, stereo ones when they have the dramatic effect you need, and to not be afraid of using mono effects when they feel right, as long as they don’t scream MONO in a multichannel field. Trying to create “perfect” sound environments that exactly duplicate real world acoustics shouldn’t be our main goal. My advice is to find ways to create compelling sound environments, regardless of the number of channels.
