WO2018092121A1

WO2018092121A1 - A device and method to reduce internal body sounds interference with otoacoustic emissions measurements

Info

Publication number: WO2018092121A1
Application number: PCT/IL2017/000008
Authority: WO
Inventors: Raphael Rembrand
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-11-17
Filing date: 2017-10-22
Publication date: 2018-05-24
Anticipated expiration: 2019-05-17

Abstract

The invention is a device and method to reduce the internal body sounds interference with Otoacoustic Emissions (OAE) measurements. Input sounds including ambient sounds and stimulus sounds reach the inner ear by utilizing two mechanisms: A) Through the ear canal / eardrum, the ossicles and then the cochlea entering through the oval window. B) Through the temporal bones and through the air next to the cochlea and the cochlear bone. Both mechanisms stimulate the cochlea and are independent of each other. Two types of output sounds are handled: A) Internal body sound e.g. breathing, blood flow friction, etc. These sounds can be measured through the eardrum and through any other bone surface near the ear e.g. the temporal bone. B) OAE response which can only be detected through the middle ear mechanism. The sound generated by the outer hair cells is transmitted through the oval window to the ossicles and then to the eardrum. The stirrup ossicles creates a tight seal for the cochlea which prevents cochlear liquid escaping from the cochlea and allows OAE to use the ossicles as their exclusive emittance path. The invention is based on the phenomenon that OAE is transmitted as output sounds (only) to the eardrum and from there into the ear canal while it is not transmitted as output sounds to the temporal bones. The present invention produces a cleaner OAE response signal by reducing the interference of body sounds when evoking an OAE response of a subject. The obtained cleaner OAE response signal is transmitted to a recorder which enables further processing of the signal(s).

Description

A DEVICE AND METHOD TO REDUCE INTERNAL BODY SOUNDS INTERFERENCE WITH OTOACOUSTIC EMISSIONS MEASUREMENTS

[0001]

FIELD OF THE INVENTION

[0002] The present invention is a device and method to reduce internal body sounds of a subject (a human being and/or animal), interfering with Otoacoustic Emissions (OAE) measurements.

[0003]

BACKGROUND OF THE INVENTION

[0001] David T. Kemp in his article "Otoacoustic emissions, their origin in cochlear function, and use", published in the British Medical Bulletin (2002;63: 223-241) states:

"Otoacoustic emissions (OAEs) are sounds of cochlear origin, which can be recorded by a microphone fitted into the ear canal. They are caused by the motion of the cochlea's sensory hair cells as they energetically respond to auditory stimulation.

[0002] OAEs provide a simple, efficient and non-invasive objective indicator of healthy cochlear function and OAE screening is widely used in universal new-born hearing screening programs. As part of the audiological diagnostic test battery, OAEs can contribute to differential audiological diagnosis, they can be used to monitor the effects of treatment and they can be helpful in the selection of hearing aids and of surgical options. As a research tool, OAEs provide a non-invasive window on intracochlear processes and this has led to new insights into the mechanisms and function of the cochlea and to a new understanding of the nature of sensory hearing impairment".

[0003] OAE is measured by emitting (broadcasting) defined stimulus sounds into the ear and recording the sounds evoked in the cochlea as a feedback to the stimulating sounds. The "cleanness" of the recorded OAE is an important component in evaluating the results obtained in OAE measurements. The term "cleanness" refers to the level of correlation between the OAE sound as generated in the cochlea and the OAE sounds, as received by the microphone without accompanying, interfering, sounds. The interfering sounds are regarded as "contaminating" sounds, referred to as "noise". Presently, OAE measurements are performed in the presence of external noises and internal body sounds. One or a combination of the following three methods deals with external ambient noises: 1) Adding an additional microphone pointing outwards, towards the incoming ambient noises, and subtracting its output from the output of the "in the ear canal" microphone, 2) using noise-cancelling algorithms, 3) conducting measurements in a quiet environment. Internal body sounds are generated by breathing; blood flow friction, etc. and they are in the range of below approximately 750 Hz. These noises are dealt with by the manufactures of OAE measuring equipment by filtering out all recorded sounds below approximately 750 Hz. It should be kept in mind that the range of approximately 150-750 Hz corresponds to a substantial portion of the frequencies of natural speech. To deal simultaneously with the external and internal noises, the stimulus is typically repeated many times with the purpose of choosing the best available result.

[0004] While the results currently obtained are useful, the present available technology does not allow for studying OAE responses to natural speech so the analysis of OAE responses to natural speech uses "harmonics". A harmonic, is defined as: whole number (integer) multiple of a fundamental frequency (source: http://www.physicsclassroom.com/class/sound/Lesson-4/Fundamental-Frequency-and- Harmonics)

[0005] The present invention is device and method to reduce the internal body sounds interference with OAE measurements, thus, enabling the studying of OAE responses in and around the speech frequency spectrum.

[0006]

SUMMARY OF THE INVENTION

[0007] The device and method to reduce the internal body sounds interference with OAE measurements is based on the understanding of how sounds are transmitted in and out of the ear and using this understanding to perform measurements in all frequency ranges.

[0008] Input sounds including ambient sounds and stimulus sounds reach the inner ear by utilizing two mechanisms: A) Through the ear canal / eardrum, the ossicles and then the cochlea entering through the oval window (shown in Fig. 1).

B) Through the temporal bones and through the air next to the cochlea and the cochlear bone.

Both mechanisms stimulate the cochlea and are independent of each other.

[0009] Two types of output sounds are handled:

A) Internal body sound e.g. breathing, blood flow friction, etc. These sounds can be measured through the eardrum and through any other bone surface near the ear e.g. the temporal bone.

B) OAE response which can only be detected through the middle ear (Fig. 1) mechanism. The sound generated by the outer hair cells is transmitted through the oval window to the ossicles and then to the eardrum. The stirrup ossicles creates a tight seal for the cochlea which prevents cochlear liquid escaping from the cochlea and allows OAE to use the ossicles as their exclusive emittance path.

[0010] The present invention is based on the phenomenon that OAE is transmitted as output sounds (only) to the eardrum and from there into the ear canal while it is not transmitted as output sounds to the temporal bones. The term "subject" in the present text typically refers to a person (a human being) and/or any animal that can generate OAE, that participates in an activity in which his OAE sounds are measured.

[0011] The term "captured" in the present text refers to sounds received by a microphone and converted to an electrical signal that can be read, amplified and recorded.

[0012] The device of the present invention produces a cleaner Otoacoustic Emissions (OAE) response signal by reducing the interference of body sounds when evoking an OAE response, of a subject. The obtained cleaner OAE response signal is transmitted to a recorder which enables further processing of the signal(s).

[0013] The device is constructed of:

1) at least one headphone mounted on the head of a subject participating in OAE- measurements. The headphone emits stimulus-sounds to the head of the subject, thus, evoking OAE sounds in the inner ear of the subject, 2) at least one contact microphone positioned in contact with the skin covering the temporal bones of the subject. The microphone "captures" body sounds from the subject and converts the sounds to output electrical signals,

3) at least one in-the-ear microphone inserted into the ear canal of the subject. The microphone "captures" the body sounds of the subject as well as the OAE sounds and converts the combined sounds to output electrical signals,

4) at least one signal-processing device which receives the electrical output signals from the contact microphone and from the in-the-ear microphone and subtracts the contact microphone's signals from the in-the-ear microphone's signals, to produce an electrical signal representing a cleaner OAE response signal. The cleaner OAE response signal is recorded and processed for further use.

[0014] Furthermore, the headphone in the device can be a bone-conducting headphone that emits the stimulus-sounds directly to the bones of the head of the subject, or alternatively can be an acoustic sound emitting headphone that emits said stimulus- sounds into the ear of the subject.

[0015] Furthermore, the headphone and bone contact microphone of the device may be connected to a connection-band.

[0016] Furthermore, the signal-processing function of the device is executed by a digital signal processor, or an analog mixer-amplifier, or a combination of both.

[0017] The method to produce a cleaner Otoacoustic Emissions (OAE) signal by reducing the interference of body sounds when evoking an OAE response, of a subject, is presently described.

[0018] In the method:

1) at least one headphone that emits stimulus-sounds to the head of a subject, thus, evoking OAE response sounds in the inner ear of the subject,

2) at least one contact microphone that "captures" the body sounds only from the temporal bones of the subject and converts the sounds to output electrical signals,

3) at least one in-the-ear microphone inserted into the ear canal of the subject that "captures" both the body sounds and OAE response sounds of the subject and converts the combined sounds to output electrical signals, 4) at least one signal-processing device that receives the electrical output signals from the contact microphone and from the in-the-ear microphone and subtracts the signals of the contact microphone from the signals from the in-the-ear microphone, to produce an electrical signal representing a cleaner OAE response signal.

[0019] Furthermore, the headphone used in the method is a bone-conducting headphone that emits said stimulus-sounds to the bones of the head of the subject.

[0020] Furthermore, the headphone used in the method is an acoustic sound emitting headphone that emits stimulus-sounds into the ear of the subject.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To better understand the present invention, and appreciate its practical applications, the following Figures are provided and referenced hereafter.

It should be noted that the Figures are given as an example only and in no way, limit the scope of the invention. Like components are denoted by like reference numerals.

[0023] Fig 1 is a schematic illustration of input and output sound-paths in the middle ear.

[0024] Fig. 2 is an illustration of a device that measures OAE outputs while reducing the interferes from internal body sounds. The device of the present invention is shown mounted on a head of an OAE-measurements participating person.

[0025]

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] Currently the accepted practice in measuring OAE responses to leave out the audio speech range below 750 Hz by filtering out all frequencies below that frequency , thus, eliminating the ability to study basic speech responses.

[0027] The present invention is a device and method to reduce internal body sounds interfering with Otoacoustic Emissions (OAE) measurements. OAE sounds are evoked and emitted as output feedback response sounds to input sounds that include stimuli, external sounds (noises) and internal body sounds. The output sounds, that can be "captured" by microphones includes body sounds, ambient sounds, stimulus-echoes and OAE sound responses. While external sounds can be controlled by conducting OAE audio measurements in a quiet location or by adding an additional ambient-sound reducing microphone, the combination of the OAE sounds and body sounds is difficult to separate. This separation is of paramount importance since body sounds mask sounds in the basic speech range below about 750 Hz.

[0028] Fig 1 is a schematic illustration of input and output sound-paths in and out of the middle ear (10). The schematic construction of the middle ear is shown in the figure and is composed of: an eardrum (tympanic membrane) (12), three ossicles, referred to as: "hammer" (14), "anvil" (16) and "stirrup" (18), cochlear bone (20) and an "oval window" (22). The sound input to the middle ear (24) is composed of a combination of external ambient sounds (also referred to as noises), stimulus audio sounds and internal sounds (28). Sensory hair cells in the cochlea (20) respond to the auditory input of sounds (24) and (28) and evoke an OAE output response (29) which is transmitted through the oval window (22), to the ossicles ((14), (16), (18)) and to the eardrum (12). The stirrup ossicle (18) creates a tight seal for the cochlea (20) which prevents cochlear liquid escaping from the cochlea and allows OAE to use the ossicles ((14), (16) and (18)) as their exclusive path leading the OAE to the oval window (22) which emits the OAE sounds (29) (only) to the eardrum (12). As a response to sound-inputs (24), (28) and (29) a combined output sound (26) out of the ear canal is created and is composed of the combined echoes from sounds of (24), the body sounds (28) and OAE sounds (29). Output sounds (29) are "captured" by an "in-the-ear" microphone (a microphone inserted into or positioned at the opening of the ear canal (21). In addition, and in parallel of output sounds (26) transmitted to the ear canal (21), output sounds are transmitted from the temporal bones (23); the output sounds from the temporal bones are designated: (27). Since the OAE sounds (29) are restricted to the ear drum (12) and aimed towards the ear canal (21), the output sounds (27) transmitted from the temporal bones (23) are a combination of the internal output body sounds (28) and the echoes of input sounds (24) and do not include the OAE sounds (29). The sounds emitted from the temporal bones (23) are "captured" by a bone contact microphone. By subtracting the output sounds "captured" by the bone contact microphone from the output sounds "captured" by the "in-the-ear" microphone a "clean" OAE response is obtained. The subtraction is done by signal-processing device.

[0029] The "captured" body sounds of the bone contact microphone and the combined sounds of the AOE and body sounds "captured" by the "in-the-ear" microphone are converted to electrical signals and is transmitted to the signal-processing device, typically (but not necessarily) by wires.

[0030] The signal-processing device, which can be a digital signal processor, or an analog mixer-amplifier, or a combination of both, receives the electrical output signals from the contact microphone and from the in-the-ear microphone and subtracts the signals from the contact microphone from the signals from the in-the-ear microphone, to produce an electrical signal representing a clean OAE response signal which can be recorded, amplified and manipulated with (measured and compared to other measurements).

[0031] Fig. 2 is an embodiment of the device of the present invention that reduces internal body sounds from Otoacoustic Emissions (OAE) sounds measurements. The device is an assembly of components (30) that reversibly connects to the head (38) of a subject which is participating in OAE-measurements. The assembly (30) is constructed of: a connection-band (33), a bone conducting headphone (32), a bone contact microphone (34), an ear canal inserted "in-the-ear" microphone (36) a signal processing device (40). Signal processing device (40) receives the "captured" output sounds by wires, as indicated in the figure, where (42) is the output wire of the contact microphone (34), (44) is the wire of the "in-the-ear" microphone (36).

[0032] Connection band (33) is a structure, typically produced from a flexible material such as, but not limited to, plastic, that reversibly mounts on the head of a subject participating in OAE-measurements and stabilizes in place, on the head of the subject, the headphone and the bone contact microphone.

[0033] In operating the device (30) defined stimulus sounds are transmitted by the bone conducting headphone (32) positioned by the band (33) in a tight-contact with a section of skin covering the temporal bones ((23) in Fig. 1)) of the skull in head (38) of an OAE-measurements participating subject. The emittance of stimulus sounds causes the production of OAE sounds ((29) in Fig. 1). The output sounds emitted from the ear canal ((21) in Fig. 1) are "captured" by ear-canal-inserted (in-the-ear) microphone (36) while the output sounds emitted from the bones (27) are "captured" by bone-contact microphone (36). The subtraction of the output sounds 'captured" by the bone contact microphone (32) from the output sounds "captured" by the "in-the-ear" microphone (36) is done by the signal processing device (40).

[0034] Another embodiment of the device of the present invention is constructed of the components described in Fig. 2 except for the usage of a bone conducting headphone (32). Instead of transmitting defined stimulus sounds by the bone conducting headphone the defined stimulus sounds are transmitted via an audio headphone into the ear canal (not shown in Fig.l).

[0035] It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope.

[0036] It should also be clear that a subject skilled in the art, after reading the present specification could adjust or amend the attached Figures and above described embodiments that would still be covered by the present invention.

Claims

I claim:

1) A device to produce a cleaner Otoacoustic Emissions (OAE) response signal by reducing the interference of body sounds when evoking an OAE response, of a subject

comprising:

at least one headphone mounted on the head of said subject, said headphone emits stimulus-sounds to the head of said subject, thus, evoking OAE sounds in the inner ear of said subject,

at least one contact microphone positioned in contact with the skin covering the temporal bones of said subject, said microphone "captures" body sounds from said subject and converts said sounds to output electrical signals,

at least one in-the-ear microphone inserted into the ear canal of said subject, said microphone "captures" the body sounds of said subject as well as the said OAE sounds and converts the combined said sounds to output electrical signals, at least one signal-processing device which receives said electrical output signals from said contact microphone and from said in-the-ear microphone and subtracts the signals from said contact microphone from the said signals from said in-the- ear microphone, to produce an electrical signal representing a cleaner OAE response signal, said cleaner OAE response signal is recorded and processed for further use.

2) The headphone of the device of claim 1, wherein the headphone is a bone- conducting headphone that emits said stimulus-sounds to the bones of the head of said subject.

3) The headphone of the device of claim 1, wherein the headphone is an acoustic sound emitting headphone that emits said stimulus-sounds into the ear of said subject. 4) The headphone and bone contact microphone of the device of claim 1, wherein the headphone and bone contact microphone are connected to a connection- band.

5) The signal-processing device of the device of claim 1, wherein the signal- processing device is a digital signal processor.

6) The signal-processing device of the device of claim 1, wherein the signal- processing device is an analog mixer-amplifier,

7) The signal-processing device of the device of claim 1, wherein the signal- processing device is an analog mixer-amplifier in combination with a digital signal processor,

8) A method to produce a cleaner Otoacoustic Emissions (OAE) response signal by reducing the interference of body sounds when measuring evoked OAE response, of a subject in which,

at least one headphone which emits stimulus-sounds to the head of a subject, thus, evoking OAE sounds in the inner ear of said subject,

at least one contact microphone "captures" the body sounds from the temporal bones of said subject and converts said sounds to output electrical signals, at least one in-the-ear microphone inserted into the ear canal of said subject "captures" both the body sounds and OAE sounds of said subject and converts the combined said sounds to output electrical signals,

at least one signal-processing device receives the said electrical output signals from said contact microphone and from said in-the-ear microphone and subtracts the signals from said contact microphone from the said signals from said in-the- ear microphone, to produce an electrical signal representing a cleaner OAE response signal.

9) The headphone of the method of claim 10, wherein the headphone is a bone- conducting headphone that emits said stimulus-sounds to the bones of the head of said subject.

10) The headphone of the method of claim 10, wherein the headphone is an acoustic sound emitting headphone that emits said stimulus-sounds into the ear of said subject.