The Influence of Immersive Sound on Listeners' Perceptions of Old Films
The purpose of this study was to investigate the influence of immersive sound on old films. Using the Halo Upmix plugin, the stereo recording of Francis Ford Coppola's The Conversation was unmixed to 5.1, 7.1, and 9.1 reproduction methods. To determine whether the addition of horizontal and height channels enhances a listener's perception of envelopment, listening tests were conducted to compare these methods. Listeners were asked to rate the sound of a sequence on a 5-point Likert scale from 1 (not enveloped to 5 (extremely enveloped). The results showed that the participants rated the 5.1, 7.1, and 9.1 reproduction methods as more enveloping than the stereo recording. When comparing the 5.1, 7.1, and 9.1 reproduction methods, listeners did not perceive significant differences.
Nugen Audio's Halo Upmix
(5.1 up mix using Halo plug-in)
* Separation of dialogue and ambient sound
* Adjustable dialogue isolation
* Each aux slider adjusts the front to rear balance
* The nodes represents each channel (The availability of solo and mute mode)
* The surround scope shows the dynamic real-time analysis of the energy distribution for the audio output
9.1 up-mix with additional vertical channels
* The 9.1 extension provides additional vertical controls over Ltm and Ram placement.
* An additional real-time analysis view for the vertical dimension, showing energy distribution of the output audio.
Procedure
1. Extract a full original stereo soundtrack from a DVD.
2. Use Nugen Audio's Halo Upmix AAX plug-in with Pro Tools HD.
3. Dialogue Isolation: keep the dialogue in the center channel.
4. Panning the aux slider of each pair of speakers.
5. Adjust the amplitude of each channel.
6. Adjust the amount of diffusion.
(Background surround sound <-> Emphasized surround sound)
Listening Tests
1. Participants will rate the stimuli in paired comparisons.
2. Before the trials begin, the listener will be provided with a definition of envelopment.
3. To address our research question, we will conduct listening tests to determine whether the addition of horizontal and height channels increases the listener's perception of envelopment.
The goal of this study was to investigate how immersive sound influences a listener’s perception of envelopment while watching old films. I believe it is worth remixing old films using immersive reproduction methods so that audiences can experience them with a greater sense of envelopment because many older films are recorded in mono or stereo. In the current study, I found that as the number of channels increased, the listeners perceived a greater sense of envelopment. Sometimes, however, the results did not show a significant difference between the 5.1 and 7.1 reproduction methods. These results were similar to those reported by Francombe et al. (2017).
In comparing the 9.1 reproduction method with the other reproduction methods, I found that the addition of two height channels played an important role in creating a greater sense of envelopment. This corresponds with the findings of Barbour (2003), who found that the addition of two loudspeakers in the vertical plane was required to achieve the perception of envelopment. It may be worth considering looking at other formats to increase the enveloping effect for old movies by using reproduction systems with more channels, especially systems with more vertical channels such as Dolby Atmos or Auro-3D.
The Halo Upmix plugin showed some limitations during the upmixing process because it is not a content-based upmixing algorithm. Except for dialogue, it cannot detect and distribute certain elements to particular channels, which results in some limitations when panning sounds. I believe a possible solution to this problem would be to employ Hyunwook Lee’s (2015) perceptual band allocation (PBA) technique. PBA captures ambient sounds with a high- pass filter and sends them to height channels, which decomposes the spectrum of the original signal and conveys it to subdivided frequency bands, mapping it to either the main or height channel layers.
It is worth noting that researchers have conducted few studies of the influence of envelopment in old films. We believe further research should be conducted to investigate what impact immersive sound may have on other old films. The current study helps provide the basis for upmixing old films in the future. The results may give mixing engineers some ideas about how to remix from stereo to multichannel reproduction methods by blending and balancing sounds for immersive environments. It would be worthwhile to study older films with a range of different reproduction methods, from mono to 22.2 channels.
<References>
Barbour, J. L. (2003). Elevation perception: Phantom images in the vertical hemisphere. In Proceedings of the Audio Engineering Society 24th International Conference on Multichannel Audio. Retrieved from: http://www.aes.org/e-lib/browse.cfm?elib=12301
Francombe, J., Brookes, T., Mason, R., & Woodcock, J. (2017). Evaluation of spatial audio
reproduction methods (Part 2): Analysis of listener preference. Journal of the Audio
Engineering Society, 65(3), 212–225.
Lee, H. (2016). Perceptual band allocation (PBA) for the rendering of vertical image spread with a vertical 2D loudspeaker array. Journal of the Audio Engineering Society, 64(12), 1003– 1013. Retrieved from: http://www.aes.org/e-lib/browse.cfm?elib=18534
