Proceedings of the Nordic Acoustical Meeting 1998 (NAM98), Stockholm, Sweden, 6-9.9.1998
DSP aspects of head-related transfer function measurements
Klaus A J Riederer
Juha Backman
Helsinki University of Technology (HUT)
Laboratory of Acoustics and Audio Signal Processing
Otakaari 5A, P.O. Box 3000, FIN-02015 HUT, Finland
Email: Klaus.Riederer@hut.fi, Matti.Karjalainen@hut.fi
Nokia Mobile Phones
P.O Box 101
00045 Nokia Group, Finland
E-mail Juha.Backman@nmp.nokia.com
This paper introduces measurements of stethoscopes and their acoustical behavior.
The two acoustical impedance matches, the one between the chest wall of a person
and the chest piece of a stethoscope and the one between the ear piece of a stethoscope
and the ear canal, have a prominent role in the acoustical function. However, in practice only
the latter one can be successfully considered. In this approach, the ear canal is modeled by a
standardized artificial ear. The compensated stethoscope responses show clear resonance structures,
caused by ¼ wavelength resonances below 1 kHz in the tubes. A Helmholz resonance limits the
usable bandwidth of stethoscopes efficiently to ca. 2 kHz.