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Research In Emerging Technologies: A Project Outline

October 15, 2013

As part of an earlier project on my MSc in Audio Production I spent some time looking at spatial audio, with the emphasis on surround sound recording techniques. Rumsey’s “Spatial Audio” (2001) is a great introduction to the subject, as is the paper by Kassier, et al (2005) that offers an informal, yet detailed comparison of available recording techniques.

This semester as part of our research module “The Dr.” and I are continuing with the theme of multichannel audio, but with the focus now on it’s reproduction, as we plan to investigate the spatial capabilities of surround sound formats.

At this stage we are still honing our specific research question, and as this is a very iterative process exact details and approaches are likely to change over the coming few weeks as background literature is reviewed and testing methods are fine-tuned. However, the basic line of the research is looking something like this…

“Is there a perceivable difference in spatial impression across surround sound formats?”

We aim to select five different formats and – using ITU-R BS.775-3 (ITU, 2012) as a reference for system setup – conduct subjective tests of approximately 20 participants in a critical listening environment, as outlined by Rumsey (2001). MUSHRA testing as defined by ITU-R BS.1534 will form the basis of the subjective assessment, as this is the most appropriate for investigating perceived spatial impression of intermediate quality audio (ITU, 2003). Prior to the listening tests, we plan to crowd-source participants by distributing an online questionnaire where gender, age and occupation data can be collected and triangulated with our subjective test results. Exact details of the questionnaire and listening test format are still to be finalised. We are also considering the logistics of participants undergoing to a basic hearing test before they can take part in the subjective tests to ensure they have an acceptable level of hearing. ITU-R recommendations stipulate that participants must be screened or ‘expert’ listeners (Bech & Zacharov, 2006). One hopes that good auditory health will assist in both the speed and efficiency of the testing and the accuracy of the results…! In order to get a more quantitative data set, we may also look at a ‘black-box’ or ‘dummy head’ testing of the different systems, and triangulate this with the results of the subjective listening tests.

Image

ITU-R BS.775-3 showing 5.1 and 7.1 speaker configurations.

Source: http://www.lsi.usp.br/interativos/nem/audience/index_eng.html

On a practical note, we have time-lined our research plan up until the date our findings will be presented, taking into account key areas such as literature reviews, questionnaire design and distribution, setting up and conducting listening tests, and statistical analysis of data. Google Calendar provides us with a shared diary to track where we are and what we need to be doing, with dropbox a shared repository for storage and organization of relevant literature and documents we are working on together. Useful web resources are bookmarked and shared on Diigo.com.

With this research project only in it’s infancy, we know roughly what we want look into, and ways to approach it, but we don’t have a hypothesis. However, despite the view of Bech and Zacharov (2006), I’m not entirely sure we need one. We can’t speculate as to whether one system is better than another, if DTS is preferred to Dolby Digital, or if SDDS is the most “immersive”. All we can do is design and conduct the tests as consistently as possible and let the participants’ results tell us if one system is perceived as being ‘better’ than the next (we may also have to try and quantify what ‘better’ is!).

Screen shot 2013-10-15 at 09.16.06

“Process diagram for the preparation of a perceptual evaluation”

From Bech & Zacharov (2006).

I guess all but the most clearly focused, instantly-inquisitive, single-minded researchers knows exactly what they want to ask along with the ‘how’ and ‘why’ from the outset. The formulation of a research question is an organic process that can go around in circles while it’s kicked into shape as the subject is explored and relevant literature reviewed. In this age of tweeting, blogging and a more liberal approach to both open education and online collaboration, the shaping and honing of our lines of investigation can only benefit from a sharing of ideas and data, and being open to the input and advice from our global network of peers out there on the world wide web. Therefore please feel free to leave comments if you have any suggestions on how we may develop our research, and get in touch if you’re in the Manchester area would like to take part in the listening tests.

Some useful links:

Bech & Zacharov’s full text can be found here, though as a more accessible introduction to perceptual audio evaluation this tutorial is a good staring point.

For the technically minded, these are ITU recommendations and EBU standards relevant to this project.

EBU-TECH 3324 (2007): EBU Evaluations of Multichannel Audio Codecs.

ITU-R BS.775-3 (2012): Multichannel stereophonic sound system with and without accompanying picture.

ITU-R BS.1116 (1997): Methods for the subjective assessment of small impairments in audio systems including multichannel sound systems.

ITU-R BS.1387 (2001): Method for objective measurements of perceived audio quality.

ITU-R BS.1534 (2003): Method for the subjective assessment of intermediate quality level of coding systems.

References:

Bech, S & Zacharov, N. 2006. Perceptual Audio Evaluation: Theory, Method and Application. Wiley. Chichester.

ITU. 2003. Recommendation ITU-R BS.1534: Method for the subjective assessment of intermediate quality level of coding systems.  Retrieved 13th October 2013, from http://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1534-1-200301-I!!PDF-E.pdf

ITU. 2012. Recommendation ITU-R BS.775-3: Multichannel stereophonic sound system with and without accompanying picture. Retrieved 12th October 2013, from http://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.775-3-201208-I!!PDF-E.pdf

Kassier, R. Lee, H-K. Brookes, T. & Rumsey, F. An Informal comparison between surround sound microphone techniques. AES convention paper 6429. Barcelona.

Rumsey, F. 2001. Spatial Audio. Oxford. Focal Press.

 

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