Probe for measuring otoacoustic emissions without ferromagnetic components

Abstract

An ear probe for measuring otoacoustic emissions, containing a. at least one microphone for measuring OAEs in the ear canal, designed as a non-magnetic electroacoustic transducer b. at least one sound source, designed as a non-magnetic electroacoustic transducer

Description

Background of the invention

[0001] Otoacoustic emissions (OAEs) are measurable sound signals actively generated in the inner ear by the outer hair cells as a side effect of the cochlear amplifier. OAEs are classified into spontaneous (SOAE) and evoked OAEs. While SOAEs are of primarily academic interest, evoked OAEs are used in audiological diagnostics. The amplitude of OAEs is typically very small, often on the order of 0 dB SPL (corresponding to 20 µPa).

[0002] SOAE measurements can be performed using only a microphone that is sealed and inserted into the ear canal.

[0003] To measure evoked OAEs, an acoustic stimulus must also be provided. For transiently evoked OAEs (TEOAEs), short-term stimuli are used, and the OAEs as a response are recorded in the time domain. For distortion product OAEs (DPOAEs), two monofrequency primary tones are presented, typically in a frequency ratio of approximately f1 / f2 = 1:1.2. The OAEs then occur, for example, at f DPOAE = 2f1-f2 on.

[0004] To measure OAE, specifically evoked otoacoustic emissions, probes are used that contain at least one sound source and at least one microphone. A schematic diagram is shown in Fig. 1 reproduced.

[0005] The probe is connected to a dedicated device for operation, which generates and / or evaluates the necessary signals and, if applicable, supply voltages. The device, or a connected computer, then typically performs a statistical analysis to reliably detect OAEs in background noise and distinguish them from the stimulus.

[0006] The probe's sound sources are typically designed as balanced armature receivers. These transducers are characterized by their small size, high efficiency, usable linearity, and sufficient bandwidth, and are primarily derived from the hearing aid industry. To measure DPOAE, two sound sources are required for the two primary tones in order to minimize technical distortion products.

[0007] Balanced armature transducers are based on the electromagnetic transducer principle and necessarily contain a permanent magnet and other ferromagnetic components.

[0008] The microphone is usually an electret microphone. For special versions, for example to implement adaptive noise cancellation (ANC), two or more microphones may be used.

[0009] Due to the magnetic materials they contain, currently commercially available OAE probes are not suitable for use in certain environments, especially in conjunction with magnetic resonance imaging (MRI) scanners. However, for functional MRI (fMRI), for example, it would be desirable to be able to use OAE probes in these environments as well. Since MRI systems are relatively noisy, noise reduction is also desirable. Description of the invention

[0010] The invention consists of an ear probe for measuring OAEs, which does not contain any magnetic materials and can therefore be used, for example, during an MRI examination.

[0011] In particular, the commonly used "balanced armature" transducers are replaced by piezoelectric transducers.

[0012] Optionally, piezoelectric transducers can also be used as microphone(s), for example newly developed MEM components.

[0013] The probe according to the invention will generally not be electrically directly compatible with existing probes because the electrical impedance of piezoelectric transducers differs significantly from that of "balanced armature" transducers.

[0014] Therefore, an additional amplifier may be necessary, meaning the probe can be "active" in this sense. This amplifier can be built directly into the probe, be a separate device, or be located in the connecting cable or connector.

[0015] The supply voltage for this amplifier is provided either by the OAE measuring device to which the probe is connected, or, to be backward compatible, by batteries or a separate power supply.

[0016] If the OAE measuring device is already designed for these converters, the additional amplifier can be omitted. Literature:

[0017] Janssen, T. and Müller, J. (2007). Otoacoustic emissions as a diagnostic tool in a clinical context, in Active Processes and Otoacoustic Emissions in Hearing, Springer Handbook of Auditory Research (Vol. 30), 421-460 (Springer).

[0018] Kemp, D.T. (1978). Stimulated acoustic emissions from within the human auditory system, J. Acoust. Soc. On. 64, 1386-1391.

[0019] Kompis M. (1999) Method and apparatus for measurement of oto-acoustic emissions impeded by disturbance noises involve disturbance noises picked up by reference microphone, filtered by adaptive filter and subtracted from distorted measurement signal. Swiss patent CH693664A5. Explanation of Fig. 1

[0020] Basic principle of an OAE probe (1). One or more sound sources (2, 3) generate a stimulus in the ear canal (6), which is coupled via a probe tip (7). A microphone (4) measures the OAE signal generated in the inner ear. An additional microphone (5) can measure external background noise to enable adaptive noise reduction. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CH 693664A5

[0019] Cited non-patent literature

[0000] Janssen, T. and Müller, J. (2007). Otoacoustic emissions as a diagnostic tool in a clinical context, in Active Processes and Otoacoustic Emissions in Hearing, Springer Handbook of Auditory Research (Vol. 30), 421-460 (Springer

[0017] Kemp, D.T. (1978). Stimulated acoustic emissions from within the human auditory system, J. Acoust. Soc. On. 64, 1386-1391

[0018]

Images