Browsing by Author "Heiskanen, Vesa"
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Item Developing an ellipsoidal reflector for measuring otoacoustic emissions(2015-06-10) Heiskanen, Vesa; Epp, Bastian; Sähkötekniikan korkeakoulu; Pulkki, VilleOtoacoustic emissions (OAEs) are faint sounds emanated by the eardrum. They can be recorded and are used as an objective measure to monitor the health of the inner ear. Conventional measurement methods use a miniature microphone housed in a probe that is fitted to the ear canal. In this thesis a novel method for measuring OAEs was experimented by using a large one-inch-diameter microphone which has the benefit of very low inherent noise. A modular ellipsoidal reflector was developed and used to collect OAEs and focus them to the microphone. The applicability of a such reflector for recording OAEs was studied. Response measurements were made to examine the acoustical properties of the different reflector setups comprised of different part-combinations. The results show that the reflector setups providing the most gain could be employed for OAE measurements where the temporal response of the measurement system is not overridingly critical such as distortion product otoacoustic emissions (DPOAEs), stimulus-frequency otoacoustic emissions (SFOAEs) or spontaneous otoacoustic emissions (SOAEs). This limitation is due to reflections in the response that take over 10 ms to decay. DPOAE measurements were made to two subjects to test the reflector measurement system in practice. Succesful measurements were accomplished at the two used stimulus frequencies which is a proof of concept that this kind of measurement system can be used to record OAEs. Further investigations are needed to be able to compare the properties of the reflector system to conventional measurement probes.Item Market entry strategies and location decisions of Finnish companies in Hungary(2006) Heiskanen, Vesa; Markkinoinnin ja johtamisen laitos; Department of Marketing and Management; Kauppakorkeakoulu; School of BusinessItem MPEG Surround -audiokoodaus(2011) Heiskanen, Vesa; Oksanen, Sami; Sähkötekniikan korkeakoulu; Eriksson, Jan
