Archaeoacoustics and Impulse Response Field Recording Research Hub

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Archaeoacoustics Scotland is the online hub and publishing portal of Nick Green, a sound designer and audio engineer working in the field of acoustic ecology and archaeoacoustics, the analysis of sound and acoustics in heritage and archaeological sites. Based in Scotland, the majority of the works presented here are from sites around Scotland. A post-graduate of ECA, Edinburgh Universities Sound Design MSc and a BA in Creative SOund Production he has been lecturing at Perth UHI for 20 years (2019).

Nick Green MSc, BA: Sector Manager of the Sound Production, Audio Engineering BScH and Theatre Arts programmes in the UHI, University of the Highlands and Islands, Perth College.

Contact:
Nick Green
Sector Manager: Audio and Theatre Arts
UHI Perth College
Crieff Road
Perth
PH1 2NX
Tel. 01738 877263
nick.green.perth@uhi.ac.uk
nick681@mac.com
 d"One of the most exciting branches of the new multi-sensory archaeology is archaeoacoustics, the archaeology of sound. In February 2014, the pioneers of this field met on the island of Malta for their first international conference. It was truly extraordinary." Kate Douglas, features editor of New Scientist writing in the foreword of 'Archaeoacoustics; The Archaeology of Sound'. This 2015 publication from the first International Multi-disciplinary Archaeoacoustics Conference, where eminent and emerging researchers gathered on the island of Malta to discuss and share methodologies and analysis of this emerging scientific, arts and humanities field: archaeoacoustics. I was fortunate enough to be in attendance for this first  international, multidisciplinary conference, it was 'truly extraordinary'. 
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Archaeoacoustics is a multidisciplinary practice by its nature requiring the knowledge of anthropologists and archaeologists, architects, acousticians, audio engineers and sound designers, historians and musicologists. As a sound designer and audio engineer I came to archaeoacoustics through the study of acoustic ecology and through conversations with archaeologists. Anthropologist Dr. Ezra Zubrow states in 'Archaeoacosutics; The Archaeology of Sound' "Indeed, many of it's practitioners do not even realise that it is a field, albeit a very immature field. Nor do they think of themselves as archaeoacousticians. Rather they consider themselves to be sound engineers, architects, musical historians, ethnomusicologits and practicing  musicians to name a few."

Primarily my research is concerned with the recording, analysis and archiving of impulse responses (IR) recorded in heritage and archaeological sites. Generally this requires man made or naturally occurring spaces used by our ancestors such as caves. However as my involvement in the subject has expanded this research has increasingly overlapped with areas of experimental archaeology, music practice, composition, sound design and musicology.

Having relatively, recently returned from the 3rd International Archaeoacoustics conference and paper presentation in Tomar, central Portugal, the field of archaeoacoustics is in rude health, but never so more scrutinised by it's practitioners from within. Having begun so enthusiastically it has now reached a stage of critical self reflection, many of it's practitioners now questioning the direction and way forward for this relatively new field of research. Indeed the next logical progression would seem to be the formation of an International Society - the International Society for Archaeoacoustic Research? For various musings from the latest conference please see the  journal entries. 

To provide context to my own niche research however, an explanation. An impulse response is the introduction of a relatively short broadband sound such as a controlled explosion and can be generated successfully by bursting a balloon, firing a starters pistol or amplifying an short burst of random noise (White Noise) through a loudspeaker system and recording the results. A more laboratory approach requires the use of a tone generator replaying a full range 20Hz to 20 KHz sine sweep, an electronically generated tone. In order to fully agitate the acoustic space at all frequencies contained in the sine sweep, playback time has usually to be between 10 and 20 seconds and played back through a reference class loudspeaker system. This sine sweep is in turn recorded using a reference class, omni-directional microphone or array of microphones; multi-channel recordings can be digitally processed to produce surround sound and ambisonic reverb algorithms. Because an IR is very short and contains the full audible range of frequencies in a single transient moment a sine sweep needs to be de-convolved in order to ‘squash’ the whole frequency range of the sine sweep into an IR. This a process of micro-processor filtering known as deconvolution, convolution reverbs are reverberation effects that have been recorded and processed from actual spaces via this method. For the computer and mathematics literate the filtering that takes place in the digital domain is known as FFT, fFast Fourier Transform function.

Author of ‘Digital Signal Processing: An Introduction’ Tae Hong Park describes an IR as “agitating a system”. In this case the agitation is the introduction of the impulse, the short broadband sound; the system is the acoustic space, a room, a hall, a cave or even within the standing stones of an ancient megalithic stone circle. Park's book covers the theory of digital audio processing in all aspects, heavy on formulae and mathematics it still provides accessible explanations at the beginning of each chapter.

Once the recorded files are digitally processed and edited they can be played back in a digital audio workstation (DAW) and used to recreate the reverberation characteristics of the space from which they were recorded. Dr. Damian Murphy of the University of York’s department of Electronics is an acoustician who curated Openairlib.net, an IR archive where the IR’s could be auditioned using anechoic recordings, unfortunately this website has recently ceased to operate - alas!.

IR’s recorded in heritage, archaeological and other sites of interest is just one facet of Digital Heritage Archiving. Having interviewed Damian in 2014 he re-itterated my own thoughts regarding the need to photographically document the sites sampled in order to provide visual context to sound recreating acoustic signatures which can be otherwise quite abstract to visualise.

How the space inhabited by our ancestors conjures up ideas of how and why these spaces might have been used for their reverberant and resonant qualities has spawned the field of research we refer to as archaeoacoustics. Sound designers and musicologists may imagine the soundscape of our ancestors and create compositions inspired by these spaces and places. Experimental archaeology when used hand in hand with applied acoustic analysis can open a world to us hitherto unimagined and unimaginable thanks in part to digital technology and this new paradigm.
A current and very exciting archaeological dig taking place at the Ness of Brodgar, Orkney is further expanding the number of Neolithic sites on the island archipelago. The site has given up evidence that it may have been a ritualistic site that was sometimes used for the mass slaughter and feasting on of large numbers of cattle. To a sound designer this paints an audio image that would be worthy of composition. The archaeological dig on Orkney is also giving rise to the hypothesis that Orkney was a significant cultural centre for our neolithic ancestors. There are so many potential angles to archaeoacoustics; it is the acoustic analysis of archaeology but so much more. Archaeoacoustics can give a ‘voice’ or soundtrack to our past.

To further quote Kate Douglas "How do you listen to the past? Obviously there are no recordings from ancient times, so you need to think laterally. Luckily, the nascent field of archaeoacoustics is not short of creative thinkers..... Not just that, they can create an acoustic fingerprint of a cave using a "sine sweep" - effectively recording the response of the space to a series of scans emitting a rainbow of all audible frequencies."

Conference Presentations and Publications:
  • Archaeoacoustics 3: More on the Archaeology of Sound: Publication of Papers from the Third International Multi-Disciplinary Conference: Volume 3, Chapter inclusion: 'Wemyss Caves Auralisation Project' N. Green 
  • Third International Multi-disciplinary Conference on Archaeoacoustics, Paper presentation 'Wemyss Caves Auralisation Project' N. Green, Tomar, Portugal 3rd - 9th October 2017
  • Perth College UHI, AES Scotland and JAMES, 24th April 2017: ‘Acoustics in Creative Spaces’ – ‘A Study of Archaeoacoustics’ N. Green
  • University of the Highlands and Islands, An Lochran, Inverness, HARC conference, February 2017: ‘Creative Collaborations’ Professor Jane Downes, Dr. Anne Bevan, Nick Green
  • Perth Museum and Art Gallery, Perth Archaeology Month, 19th June 2015: ‘Re-imaging Space’ Dr. P. Oliver and N. Green
  • ​Leeds College of Music, International Festival of Artistic Innovations, 12th March 2015: ‘Re-imagining Space; The Guerilla Impulse and DIY Culture’ Dr. P. Oliver and N. Green
  • Perth College UHI Staff Conference, 18th June 2014: ‘Archaeoacoustics; Impulse Response Archiving of Heritage Sites’ N. Green
  • First International Multidisciplinary Conference on Archaeoacoustics, Corinthian Palace Hotel, Malta 19th, 20th, 21st, 22nd February 2014: Conference delegate
  • International Journal of Acoustic Ecology, November 2013, Feature Article ‘Sampling the Past’ N. Green  

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