Neuroscience Letters 584 (2015) 162–167 Contents lists available at ScienceDirect Neuroscience Letters jo ur nal ho me p age: www.elsevier.com/locate/neulet Automatic detection of unattended changes in room acoustics Johannes Daniel Frey ∗ , Mike Wendt, Thomas Jacobsen Experimental Psychology Unit, Helmut Schmidt University/University of the Federal Armed Forces, Hamburg, Germany h i g h l i g h t s • An auditory automatic detection of changing room acoustics is proposed. • A passive oddball protocol including auditory stimuli with deviating room acoustics was used. • Violation of auditory regularities with respect to room acoustics resulted in a mismatch negativity. • The mismatch negativity reflects automatic detection of violations of auditory regularities. • Violation of auditory regularities due to changed room acoustics are detected automatically. a r t i c l e i n f o Article history: Received 11 July 2014 Received in revised form 12 September 2014 Accepted 29 September 2014 Available online 6 October 2014 Keywords: Event-related potentials (ERP) Mismatch negativity (MMN) Pre-attentive auditory processing Auditory space perception Virtual acoustics Auditory room effects a b s t r a c t Previous research has shown that the human auditory system continuously monitors its acoustic envi- ronment, detecting a variety of irregularities (e.g., deviance from prior stimulation regularity in pitch, loudness, duration, and (perceived) sound source location). Detection of irregularities can be inferred from a component of the event-related brain potential (ERP), referred to as the mismatch negativity (MMN), even in conditions in which participants are instructed to ignore the auditory stimulation. The current study extends previous findings by demonstrating that auditory irregularities brought about by a change in room acoustics elicit a MMN in a passive oddball protocol (acoustic stimuli with differing room acoustics, that were otherwise identical, were employed as standard and deviant stimuli), in which par- ticipants watched a fiction movie (silent with subtitles). While the majority of participants reported no awareness for any changes in the auditory stimulation, only one out of 14 participants reported to have become aware of changing room acoustics or sound source location. Together, these findings suggest automatic monitoring of room acoustics. © 2014 Elsevier Ireland Ltd. All rights reserved. 1. Introduction The mismatch negativity (MMN), component of the human event-related brain potential (ERP), is a well-established measure for the investigation of pre-attentive auditory processing. The MMN is widely considered to reflect detection of violations of regularities extracted from the acoustic environment, that occurs even when the acoustic stimulation is not in the focus of attention [1]. In the simplest form, it is observed when a repeated sound (standard) is followed by a differing sound (deviant) at an unpredictable time. A mechanism that constantly monitors the acoustic environment and detects changes is likely to govern this process [2,3]. Differ- ent auditory dimensions have been shown to elicit MMN. So far, the four first-order auditory regularity violation dimensions that ∗ Corresponding author at: Holstenhofweg 85, D-22043 Hamburg, Germany. Tel.: +49 40 6541 2794; fax: +49 40 6541 3604. E-mail address: Johannes.Frey@hsu-hh.de (J.D. Frey). have been found to elicit a MMN are pitch [4–6], duration [7–9], loudness [10,11] and sound source location [12–14]. Higher-order auditory regularity violation dimensions eliciting a MMN have also been reported, for instance the omission of a tone in a recurrent pattern [15,16], or by speech stimuli violating abstract phonological rules followed by a sequence of standard stimuli [17]. Another auditory dimension that bears importance for percep- tion and behavior, particularly in real life contexts, relates to sound properties arising from the reflecting characteristics of objects that make up the environment of the sound source-perceiver system. In a built-up environment as well as in a considerable portion of the natural environment, virtually all sound is affected by this phenomena, referred to as room acoustics. Previous research has shown that room acoustics impact both perceptual quality and behavioral performance. For instance, the reverberation time of a room influences the ability to localize the sounds, especially for the localization of continuous broadband noise [18]. Behavioral relevance of room acoustics has been demonstrated for (musical) sound production (i.e., professional piano players adapted their http://dx.doi.org/10.1016/j.neulet.2014.09.050 0304-3940/© 2014 Elsevier Ireland Ltd. All rights reserved.