This item is available under a Creative Commons License for non-
commercial use only 1.2 COMPUTER AND INFORMATION SCIENCE,
Geosciences, (multidisciplinary) In this paper we evaluate the
innate ability of mobile phone speakers to produce ultrasound
and the possible uses of this ability for accurate indoor
positioning. The frequencies in question are a range between 20
and 22 KHz, which is high enough to be inaudible but low enough
to be generated by standard sound hardware. A range of tones is
generated at different volume settings on several popular modern
mobile phones with the aim of finding points of failure. Our
results indicate that it is possible to generate the given range
of frequencies without significant distortions, provided the
signal volume is not excessively high. This is preceded by the
discussion of why such ability on off-the-shelf mobile devices
is important for Location Based Services (LBS) applications
research. Specifically, this ability could be used for indoor
sound trilateration positio