Audio stimulator for conditions with zero tolerance against electromagnetic interence
The KAR ADU insert headphones, designed by Unides Design Ay, replaces headphones / loudspeakers in surroundings where electromagnetic interference fields cannot be allowed.
The electrodynamic transducer (sound source) and the control electronics
of the stimulator are enclosed in a moulded aluminum box, from
which sound is transmitted via plastic / silicone tubes to a
porous EAR-tip acting as an earphone. The stimulator box is placed outside the shielding room (or far away from the sensitive equipment) and only the plastic tubes conveying the sound waves are placed inside the shielding room so that no electromagnetic interference is created there. The use of replaceable EAR-tips allows 100 % hygienic use of the insert-type headphone.
The stimulator is driven by a normal sound amplifier yielding at least
100 W RMS / 8 ohm (per channel). The passive sound source requires
no power supply. The KAR ADU audio stimulator is a single channel device, hence a binaural
system consists of two units.
The passive ADU headphones are not digitally equalized, instead the equipment is well electro-acoustically
designed so that a maximum flat frequency range is obtained. The problem with digital equalization is that it requires additional hardware whilst limiting the dynamic range of the stimulus. Also,
the equalization can only be done in generic way (based on artificial ear measurements), which creates more or less artifacts in the the individual listening experience. Of course,
the EAR-tips need to be properly fitted at the ear canals in order to avoid leaks that would degrade the quality of the
sound reproduction and cause imperfect background noise cancellation.
KAR ADU1c & ADU2a audio stimulator
There are currently two different models of the KAR audio stimulator available. The newest design (02/2006) insert headphones are model KAR ADU1c, with a total tube length of 3.25 m.
The other model is KAR ADU2a (02/2004), with a total tube length of 5.3 m.
Download the product specifications in PDF below.
The ADU audio stimulators are in use, e.g., in the following research institutions:
- Helsinki University of Technology (HUT), Finland / Low temperature laboratory / Brain Research Unit
- Leibniz Research Centre for Working Environment and Human Factors (IFaDo), Germany / Cognitive Neurophysiology (two different models)
- Massachusetts General Hospital (MGH), USA / Massachusetts Institute of Technology (MIT) / HMS Martinos Center (two different models)
- Helsinki University of Technology (HUT), Finland / Advanced Magnetic Imaging Centre
- Helsinki University Central Hospital (HUCH), Finland / BioMag Laboratory
- Radboud University, The Netherlands - F.C. Donders Centre
- Aarhus University, Denmark - Center of Functionally Integrative Neuroscience (CFIN)
- Alternative Energies and Atomic Energy Commission, France - INSERM-CEA Cognitive Neuroimaging Unit
- ULB-Hôpital Erasme, Belgium / Department of Nuclear Medicine / Magnetoencephalography Unit
- Aalto University, Finland / Aalto TMS Laboratory
Literature - reports, empirical verification
References - research
The ADU audio stimulators have been used, e.g., in the following published studies (in addition to the above):
Human cortical representation of 3-dimensional sounds: differences
between azimuth and elevation (Nobuya Fujiki, Klaus A J Riederer, Veikko
Jousmäki, Jyrki Mäkelä & Riitta Hari).
In Society for Neuroscience 31st Annual Meeting, San Diego, CA, USA, 10.-15.11.2001.
Human cortical representation of virtual auditory space: Differences
between sound azimuth and elevation (Nobuya Fujiki, Klaus A J Riederer,
Veikko Jousmäki, Jyrki Mäkelä & Riitta Hari)
European Journal of Neuroscience, Vol. 16, pp. 2207-2213, 2002.
Processing of sound location in human cortex (Jörg Lewald, Klaus A J Riederer, Tobias Lentz, Ingo G Meister)
European Journal of Neuroscience, Vol. 27, pp. 1261-1270, 2008.
Model KAR ADU1c audio stimulator, 4th generation model (latest in production).