The AUralization and Reproduction of Acoustic Sound-fields (AURAS) Facility

SPRAL Alumni Graduate Students: Matthew Neal, Ph.D. and David Dick, Ph.D.

For a short virtual tour of our lab facility – the AUralization and Reproduction of Acoustic Sound fields (AURAS) facility, check out this video.

The AUralization and Reproduction of Acoustic Sound-fields (AURAS) facility is a 32 channel loudspeaker array for acoustic simulation. For a short virtual tour of AURAS, check out this video. The loudspeaker array is built in an anechoic chamber at Penn State, and it consists of 30 distributed loudspeakers and two sub-woofers.  All channels of the array are controlled independently, and can be processed for any type of virtual acoustic reproduction.  The array is controlled with a 32 channel digital to analogue converter, and powered by three 12 channel amplifiers and one 2 channel amplifier.

The AURAS facility is used to conduct subjective studies in concert hall acoustic perception, through both reproduction of measured halls and simulation of virtual halls.  Using the Eigenmike, higher order ambisonics allows us to reproduce the measured sound field within our array. Subjects can sit within the array, listen to different concert hall auralizations, and rate the auralizations on different subjective perceptions.  The facility is equipped with a wireless touchscreen monitor, allowing subjects to answer questions about the concert hall simulations and interact with the sound field. Max 7 has been used to control the loudspeaker array, because it which enables real-time switching between concert hall stimuli and easy-to-use interface development.

The construction of the array involved the individual construction of all 30 loudspeakers within the facility, and individual equalization of each loudspeaker to ensure as accurate sound field reconstruction as possible. Each loudspeaker is controlled through a USB interfaced digital to analog converter and three multi-channel amplifiers. The facility was also built with a height-adjustable chair, for accurate subject positioning.

Sub-woofers

In 2017, two custom-built sub-woofers were added to the array. Each used an 18″ driver, rated down to 20 Hz. Digital filters were developed to cross over from the 30 array loudspeakers to the 2 sub-woofers at 80 Hz, extending the low-frequency capabilities of the facilities. A 2 channel amplifier was added to the previously existing equipment, and the two unused channels of the 32 channel converter were connected to control the sub-woofers. With only two sub-woofers, ambisonic processing cannot be done, so only the omnidirectional component of the low-frequency energy is output over the sub-woofers.

 

Details of facility can be found in Neal’s M.S. Thesis:

• Neal, M. (2015). “Investigating the sense of listener envelopment in concert halls using third-order Ambisonic reproduction over a loudspeaker array and a hybrid room acoustics simulation method.” M.S. Thesis, The Pennsylvania State University.

Peer-Reviewed Publications of Projects that have used AURAS:

• Dick, D.A.* and Vigeant, M.C. (2019). “An investigation of listener envelopment utilizing a spherical microphone array and third-order ambisonics reproduction.” J. Acoust. Soc. Am. 145: 2795-2809
• Lawless, M.S.* and Vigeant, M.C. (2017). “Effects of test method and participant musical training on preference ratings of stimuli with different reverberation times.” J. Acoust. Soc. Am. 142: 2258-2272

Conference Proceedings of Projects that have used AURAS:

• Neal, M.T.,*, Vigeant, M.C. (2019). “Predicting an individual’s preference in concert halls from measurement-based auralizations.” Int. Sym. on Room Acoustics, Amsterdam, NL, 8 pages. [Invited, Best student paper award]
• del Solar Dorrego, F.M.* and Vigeant, M.C. (2018). “A study of the just noticeable difference of early decay time (EDT).” Inst. of Acoust. 10^th Int. Conf. on Auditorium Acoust. Hamburg, Germany, 10 pages
• Neal, M.T.* and Vigeant, M.C. (2015). “Subjective study on listener envelopment using hybrid room acoustics simulation and higher order Ambisonic reproduction.” Inst. of Acoust. 9^th Int. Conf. on Auditorium Acoust. Paris, France, 8 pages
• Dick, D.A.* and Vigeant, M.C. (2015). “Investigation of listener envelopment and the late sound field using spherical microphone array impulse response measurements.” Inst. of Acoust. 9^th Int. Conf. on Auditorium Acoust. Paris, France, 9 pages

Recent Conference Presentations (Abstracts) of Projects that have used AURAS:

• Broyles, J.M.*, Vigeant, M.C., and Sparrow, V.W. (2019). “Perceived annoyance of Mach-cutoff flight ground signatures compared to common transportation sounds.” J. Acoust. Soc. Am. 146:2782
• Lawless, M.S.*, Rusk, Z.T.*, Vigeant, M.C., and Dittberner, A (2019). “Effect of trading-off office background and intermittent noise levels on performance, annoyance, distraction, and stress.” J. Acoust. Soc. Am. 145:1900
• Ortega, N.D.*, Vigeant, M.C., and Sparrow, V.W. (2019). “Identifying metrics to predict annoyance due to Mach-cutoff flight ground signatures.” J. Acoust. Soc. Am. 145:1899 [Invited]
• Neal, M.T.,* and Vigeant, M.C. (2018). “Achieving realism and repeatability of an orchestra simulated within a concert hall.” J. Acoust. Soc. Am. 143:1824 [Invited]
• Dick, D.A.* and Vigeant, M.C. (2016). “Relating listener envelopment to specific time segments in early and late portions of sound fields (A).” J. Acoust. Soc. Am. 139:2088 [Invited, Best Student Paper Award]