Device and method for measuring clinical audiometry parameters

Abstract

The present invention discloses a device and method for measuring middle ear impedance for clinical audiometry research in a wide frequency range of ambient pressure, which is based on MEMS microphone technology and uses a pressure-pressure probe to measure sound pressure waves and corresponding sound velocity waves.

Description

Technical Field

[0001] The present invention relates to a device and method for measuring middle ear impedance in a simple, non-invasive, reliable and economical manner for clinical audiometry research.

[0002] The present invention is based on MEMS microphone technology and uses a pressure-pressure probe to simultaneously measure the sound pressure wave and the corresponding sound velocity wave.

[0003] The present invention mainly relates to impedance audiometry, also known as tympanometry, for diagnostic applications to determine the status of the tympanic membrane in the middle ear of humans or other animals (such as dogs or cats) having an ossicular tympanic system and an external auditory canal. Background Art

[0004] Typical tympanometry allows for an objective analysis of the functional status of the outer and middle ears to diagnose major pathologies. This measurement method includes sending single-frequency sound waves typically around 226, 678, 800, and 1000 Hz, and evaluating the change in the acoustic volume impedance measured at the tympanic membrane as the pressure artificially generated in the external auditory canal (usually in the range of -600 to +400 daPa) changes.

[0005] This typical tympanometry has some drawbacks. In fact, typical tympanometry is performed by indirect measurement and invasive methods using single-frequency stimuli, which is particularly irritating, especially for infants and children, due to the externally induced change in the static pressure within the ear canal.

[0006] As an alternative to this typical tympanometry, a broadband tympanometry using a p-v microprobe has also been developed. This method detects the relationship between the specific admittance of the system (including the ear canal and the tympanic membrane) and the sound wave frequency from 50 Hz to 8 kHz under a constant static pressure. This method is based on a microprobe p-v (pressure-velocity) using MEMS technology (microelectromechanical systems) and is capable of directly measuring the pressure value and the velocity value in response to an external stimulus.

[0007] However, the disadvantages of this technique are the high cost of the p-v probe and the fact that the velocity probe is relatively fragile and prone to breakage. Summary of the Invention

[0008] The object of the present invention is to overcome the above-mentioned drawbacks and conduct clinical audiometry research on the functional status of the ear in a reliable, non-invasive and economical manner.

[0009] According to Kren Monrad et al. reported in "Reproducing ear-canal reflectance using two measurement techniques in adult ears", The Journal Of The Acoustical Society Of America, American Institute Of Physics For The Acoustical Society Of America, New York, NY, US, vol.147, no.4, 17 April 2020 (2020-04-17), pages 2334-2344, XPO12246238, ISSN: 0001-4966, DOI: 10.1121 / 10.0001094 that the measurement uncertainty of ear-canal reflectance associated with traditional measurement techniques was studied by reproducing ear-canal reflectance measurements using two different measurement techniques.

[0010] The specific subject of the present invention is a method for determining ear-canal admittance for clinical audiometric studies, the method comprising at least one or more iterations of a procedure, wherein each iteration is associated with a corresponding coupling configuration (Q, Q1, Q2) between an impedance probe and the ear canal, and wherein the procedure comprises the following steps:

[0011] A. Coupling a calibrated sealed impedance probe having a known air volume V 探针 to the ear canal through its first end such that:

[0012] - The air volume V 探针 sealed within the impedance probe and the air volume V 耳道 within the ear canal constitute a total air volume V 总 , and

[0013] - The longitudinal axis of the impedance probe substantially coincides with the longitudinal axis of the ear canal;

[0014] B. Sending a broadband excitation sound signal s(t) into the ear canal through a loudspeaker of the impedance probe, the loudspeaker being located at the second end of the impedance probe opposite the first end;

[0015] C. Directly detecting the sound pressures p1(t), p2(t) returning from the ear canal at at least two points x1 and x2 located on the longitudinal axis of the impedance probe (1) and separated by a distance Δx 12 therebetween, by means of a microphone array included in the impedance probe and outputting electrical signals r1(t) and r2(t); and

[0016] D. Obtain and discretize the output electrical signals r1(t) and r2(t) from the microphone array, and respectively obtain the discretized signals r1(n) and r2(n), where n ∈ [1; N].

[0017] E. Calculate the first impulse response through the following equation and the second impulse response

[0018]

[0019]

[0020] where s′(t) is the time-reversed broadband acoustic signal s(t), FFT is the Fast Fourier Transform, and IFFT is the Inverse Fast Fourier Transform.

[0021] F. Calculate the impulse responses of the acoustic pressure p1(t) and p2(t) of the air particles at the measurement point x0 along the longitudinal axis of the impedance probe and the velocity impulse response

[0022]

[0023]

[0024] The measurement point x0 is the center point between points x1 and x2.

[0025] G. As shown below, multiply the impulse responses of pressure and velocity by the prior-known calibration constants α and β respectively, and convert the impulse responses of pressure and velocity to physical units of pressure and velocity:

[0026]

[0027]

[0028] H. As shown below, calculate the spectra of the (270) pressure and velocity impulse responses respectively through the Fast Fourier Transform

[0029]

[0030] where ω m is the discrete frequency, where m ∈ [1; N / 2];

[0031] I. Calculate the admittance which is the cross-spectrum of the acoustic pressure impulse response spectrum and the acoustic velocity impulse response spectrum and the auto-spectrum of the acoustic pressure impulse response spectrum Ratio:

[0032]

[0033] L. According to the following formula, obtain the calibrated spectrum of admittance through a priori known calibration function Γ(ω m )

[0034]

[0035] Steps D to L are performed by a control processing device.

[0036] According to another aspect of the present invention, the calibration constants α and p and the calibration function Γ(ω m ) are a priori known, optionally provided by the microphone manufacturer.

[0037] According to another aspect of the present invention, the excitation sound signal s(t) can be a swept-frequency signal, optionally a linear or logarithmic sine signal, within a time T 扫频 less than 10 seconds, optionally equal to 2 seconds, more optionally equal to 1 second, from a minimum frequency F greater than 100 Hz 最小 changing to a maximum frequency F less than 5000 Hz 最大 .

[0038] According to another aspect of the present invention, the distance Δx 12 can be equal to 12 mm.

[0039] According to another aspect of the present invention, step B may include sub-steps:

[0040] B.1 Synthesize a digital swept-frequency signal s(n) through a signal generator,

[0041] B.2 Convert the digital swept-frequency signal s(n) into a broadband excitation sound signal s(t), and input it into the speaker through a D / A converter.

[0042] According to another aspect of the present invention, step D can be performed by an A / D converter synchronized with the D / A converter.

[0043] According to another aspect of the present invention, the calibrated spectrum of admittance can be further input to a display for display.

[0044] According to another aspect of the present invention, the impedance probe and the ear canal can be coupled in a first coupling configuration (Q1), and the excitation sound signal s(t) can be a fast swept-frequency signal s changing within a time less than 1 second 快 (t) to obtain a first calibrated admittance And the program may further include additional steps:

[0045] M. Check the calibration admittance to see if the resonance condition is satisfied, such that the peak of the first calibration admittance of the module corresponds to the zero crossing of its phase, and wherein:

[0046] - If the resonance condition does not occur, perform another iteration of the program including steps A to M, wherein the impedance probe and the ear canal are coupled in another coupling configuration (Q2) different from the previous coupling configuration (Q1), and the excitation acoustic signal s(t) is a fast sweep signal s 快 (t);

[0047] - If the resonance condition occurs, perform steps B to L of the program, wherein the coupling configuration is the configuration in which the resonance condition occurs, the excitation acoustic signal s(t) is a sweep signal whose frequency varies within a time greater than that of the fast sweep signal s 快 (t), and one or more iterations of the program end.

[0048] Another specific subject of the present invention is a method for clinical audiometry research, including the method for determining the ear canal admittance according to the present invention, wherein the research is performed in the coupling configuration (Q, Q1, Q2) of the last one or more iterations, and wherein the frequency of the excitation acoustic signal s(t) varies within a time greater than or equal to 1 second.

[0049] Another specific subject of the present invention is a device for performing the method for determining the ear canal admittance according to any one of claims 1 to 7, comprising:

[0050] - An impedance probe configured to be coupled to the ear canal (6), having

[0051] - A box-shaped body having a first end configured to be coupled to the ear canal,

[0052] - A speaker near the second end of the box-shaped body opposite to the first end, configured to emit an excitation acoustic signal, the box-shaped body being sealed and containing normal-pressure air with a volume V 探针 ;

[0053] - A microphone array housed in the box-shaped body and configured to detect the signal returned from the ear canal, the microphone array including at least a first microphone and at least a second microphone, the distance between them being Δx 12 and depending on the frequency of the excitation acoustic signal s(t), each microphone being configured to directly detect the returned acoustic pressure p(x, t) varying with time t and output an electrical signal r(x, t);

[0054] - A control and processing device, configured to control and process the input and output signals of the impedance probe and perform steps B to L, having:

[0055] - A generating unit, configured to generate a digital signal s(n) and send it to a loudspeaker through a D / A conversion board detachably coupled to the loudspeaker, and

[0056] - A sound acquisition board, configured to acquire an output signal from a microphone array through an A / D conversion board detachably coupled to the microphone array (8),

[0057] The impedance probe and the control and processing device are detachably coupled to each other.

[0058] According to another aspect of the present invention, the control and processing device may further be configured to perform the step M.

[0059] According to another aspect of the present invention, the box-shaped body may be a hollow cylinder.

[0060] According to another aspect of the present invention, the device may be configured to input a broadband excitation sound signal s(t) with a frequency of 100 Hz to 5000 Hz, where the distance Δx 12 is equal to 12 mm.

[0061] According to another aspect of the present invention, the second end is equipped with an adapter, which is configured to be easily coupled to the ear canal, and optionally the adapter is detachable.

[0062] According to another aspect of the present invention, the adapter is frustum-shaped and optionally made of rubber latex.

[0063] Compared with the solutions of the prior art, the method provided by the present invention has many and important advantages.

[0064] The method of the present invention is non-invasive because it can measure the acoustic admittance at the entrance of the ear under ambient pressure without changing the static pressure in the patient's ear canal. Another advantage is that it allows the analysis of the functional state of the ear in a relatively wide frequency range. In addition, measuring the acoustic admittance of the ear using the p-p (pressure-pressure) technique allows the use of a pressure probe based on MEMS technology, i.e., a microphone, thereby reducing the production cost of the impedance probe.

[0065] To measure the acoustic admittance in the ear canal, which is the reciprocal of acoustic impedance, it is necessary to measure the pressure and velocity signals obtained in response to a sound stimulus emitted at the entrance. The p-p technique is based on the Euler acoustic wave equation, which allows the reconstruction of the acoustic particle velocity signal by numerically integrating the gradient signal of the time-varying acoustic pressure. From a metrological point of view, this choice is not optimal in many respects, but it is satisfactory within the frequency range required for the application, and due to the commercial success of MEMS technology applied to pressure microphones, the production cost of the probe can be significantly reduced at present. Description of the Drawings

[0066] Now, the present invention will be described with reference to the preferred embodiments of the present invention, and particularly with reference to the drawings but not in a limiting manner, wherein:

[0067] Figure 1 is a schematic block diagram of a preferred embodiment of the device for measuring the acoustic admittance of the ear according to the present invention;

[0068] Figure 2 is a flowchart of the algorithm executed by the first preferred embodiment of the method for measuring the acoustic admittance of the ear according to the present invention;

[0069] In these drawings, the same reference numerals will be used for the same elements. Detailed Description of the Preferred Embodiments

[0070] Due to the structure of the ear canal, the air is restricted to oscillate substantially along the longitudinal axis of the ear canal. Therefore, the velocity vector can be approximated by the velocity along the said axis, which we set as the x direction or the x-axis.

[0071] Reference Figure 1 , the device 100 includes an impedance probe 1, and the impedance probe 1 has a box-shaped body 2, the first end 3 of which is configured to be coupled to the external measurement environment. In Figure 1 the case shown, the external measurement environment is the external auditory canal 6 of the patient. The box-shaped body 2 contains at least one loudspeaker 4 therein, and the loudspeaker 4 is placed near the second end 5 of the box-shaped body 2 opposite to the first end 3.

[0072] The loudspeaker 4 is configured to emit an acoustic signal s(t) input to the external auditory canal 6.

[0073] Figure 1 The box-shaped body 2 of the preferred embodiment has a hollow cylindrical shape. Generally, we set the position x a along the x-axis of the first end 3 as the origin of the x-axis, and x a = 0.

[0074] The box-shaped body 2 is rigid and is optionally made of brass or rigid resin. The box-shaped body 2 is sealed and contains a known volume V 探针atmospheric air. The coupling of the impedance probe 1 to the patient's external auditory canal through its first end 3 causes the air volume V 探针 and the air volume V 耳道 within the ear canal to constitute the total atmospheric air volume V 总 , i.e., V 总 = V 探针 + V 耳道 . In other words, when the impedance probe and the ear canal are coupled together, the total volume V 总 containing atmospheric air is restricted by the impedance probe and the ear canal.

[0075] Furthermore, the coupling causes the axis passing through the geometric centers of the first end 3 and the second end 5 (usually the longitudinal axis of the impedance probe) to be parallel and substantially coincident with the axis of the ear canal (i.e., the x-axis).

[0076] In a preferred embodiment, the first end 3 is equipped with an adapter 7, which optionally has a frustoconical shape and is made of rubber latex, configured to facilitate coupling to the external auditory canal 6. The adapter 7 is detachable for replacement or cleaning before use on different patients.

[0077] The microphone array 8 is configured to detect the return signal from the external auditory canal 6 and is placed in the box-shaped body 2. The microphone array 8 includes a first microphone 9 and at least one second microphone 10, and each microphone is configured to directly detect the return sound pressure p(x, t) varying with time t at a first measurement point x1 and a second measurement point x2, respectively, and provide an electrical signal r(x, t).

[0078] The distance Δx 12 between the first measurement point x1 of the first microphone 9 and the second measurement point x2 of the second microphone 10

[0079] depends on the frequency of the target signal. Ideally, in order to reconstruct the velocity signal from the pressure signals measured by the two microphones, a different distance Δx should be used for each frequency (i.e., each wavelength) of the sound field to be measured.

[0080] In a preferred embodiment, an optimal distance is used to cover the operating frequency range. To reduce the experimental error in the reconstruction of the velocity signal due to the finite difference approximation error at high frequencies, the measured wavelength must be greater than approximately six times the distance between the two microphones. For example, when the distance between the probes is equal to 50 mm, the high-frequency limit of the sound field where the experimental error significantly increases is 1.25 kHz; when the distance is equal to 12 mm, the high-frequency limit is 5 kHz; when the distance is 6 mm, the high-frequency limit is 10 kHz. 12 When performing impedance measurements in the human ear canal, the distance Δx

[0081] is equal to 12 mm to optimize the admittance measurement in the frequency range of 100 - 5000 Hz.In other embodiments of the present invention, the microphone array 8 includes a plurality (more than two) of microphones that are spaced apart from each other by different distances Δx ij so as to obtain a more accurate reconstruction of the velocity signal for each frequency range.

[0082] The minimum distance on the longitudinal axis between the second end portion 5 and the center point x0 of the microphone array 8, i.e., the minimum distance between the first measurement point x1 and the second measurement point x2, must minimize the measurement error of the microphone array 8 due to proximity to the sound source. In a preferred embodiment, this distance is equal to 35 millimeters.

[0083] The impedance probe 1 is detachably coupled to a control processing device 11 that is configured to control and process input and output signals from the impedance probe 1. The control processing device 11 includes a generating unit 12 and a sound acquisition board 14. The generating unit 12 is configured to generate a digital signal s(n) and send it to the speaker 4 through a D / A conversion board 13 that is detachably connected to the speaker 4. The sound acquisition board 14 is configured to obtain an output signal from the microphone array 8 through an A / D conversion board 15 that is detachably connected to the microphone array 8. The generating unit 12 and the sound acquisition board 14 are connected to each other. Optionally, the control processing device 11 is detachably connected to one or more devices, such as a PC, a smartphone, and a tablet computer, and / or connected to one or more screens 16 that are configured to display the signals controlled and processed by the control processing device 11.

[0084] To measure the acoustic admittance in the ear canal, it is necessary to measure the sound pressure and particle velocity signals in the air obtained in response to a sound stimulus (i.e., an input signal) sent at its entrance. As Figure 1 shown, the impedance probe 1 allows an indirect measurement of the velocity signal starting from two sound pressure signals detected at a distance Δx from each other along the axis of the probe itself.

[0085] In fact, by considering a one-dimensional sound field in a medium of density ρ, the Euler acoustic equation that relates the sound pressure p(x,t) and the particle velocity v(x,t) to a point in the sound field can be written as:

[0086]

[0087] From which the velocity signal can be obtained by integration:

[0088]

[0089] By using the finite difference approximation method, in practice the pressure gradient can be estimated by measuring the pressure at two closely spaced points A and B that are at a distance Δx apart:

[0090]

[0091] It should be noted that this approximation is valid only when Δx is small compared to the shortest wavelength in the measured sound field.

[0092] Substituting Equation 3 into Equation 2, the velocity is calculated as follows:

[0093]

[0094] Similarly, the sound pressure can be estimated as the average value of the pressures p(A)ep(B).

[0095] Therefore, for the impedance probe 1, the spatial derivative of the approximate pressure can be taken with its increment ratio Δx 12 and a time integration is performed to obtain the velocity signal component in the x - direction:

[0096]

[0097] and the pressure is calculated as follows:

[0098]

[0099] where

[0100]

[0101] where p1(x1, t)e p2(x2, t) are the pressure signals measured by the first microphone 9 and the second microphone 10.

[0102] The pressure and velocity signals calculated by Equations 5 to 7 are generally considered to be related to the center point x0 between the two microphones, that is, the actual measurement points {p(x0, t); v(x0, t)}.

[0103] To identify a linear time - invariant acoustic system, such as the ear canal of a human or mammalian ear, its transfer function must be known so that its response to sound waves of any frequency can be analyzed. However, the study of impedance requires knowledge of the two sound pressure and sound velocity responses in the frequency domain. Therefore, the most suitable stimulus for measuring these responses must be able to excite the system over the entire frequency range planned for analysis. Thus, the stimulus must be generated by a signal with the same average temporal energy for each frequency component. Therefore, the calculation of admittance is based on the impulse response of a linear time - invariant acoustic system, which is calculated from the measurement of the field excited by a chirp or swept - frequency signal (i.e., a frequency - modulated signal with an instantaneous frequency that varies linearly with time):

[0104]

[0105] where δ(t) is the impulse response, IFFT is the inverse fast Fourier transform, FFT(s′(t)) is the fast Fourier transform of the time-reversed swept signal, and FFT(r(t)) is the fast Fourier transform of the signal measured as the system’s response to the swept signal stimulus.

[0106] The flow chart of the preferred embodiment of the ear acoustic admittance measurement method is as follows Figure 2 As shown, located at Figure 1 In a frame corresponding to the control processing device 11 of the device 100;

[0107] First, the impedance probe 1 is calibrated, for example using a standard calibration method used in tympanometric manometry, to calculate the air volume V contained within the impedance probe 1. 探针 For example, a typical method is one well known to those skilled in the art, which uses three known volumes of air (0.2 ml, 2 ml, and 4 ml).

[0108] In an initial step, the calibrated impedance probe 1 is coupled to the ear canal 6 via its first end (3) in a coupling configuration (Q) such that its air volume V 探针 and the volume of air in the ear canal V 耳道 The total air volume V 总 , that is, V 总 =V 探针 +V 耳道 , its longitudinal axis is parallel to the axis of the ear canal (ie, the x-axis) and basically coincides with it.

[0109] The coupling configuration refers to the mutual contact arrangement of the impedance probe 1 and the ear canal 6 .

[0110] In step 200, the generating unit 12 generates a signal for a time T of less than 10 seconds, optionally equal to 2 seconds, and even more optionally equal to 1 second. 扫频 The minimum frequency F that generates (or synthesizes) a frequency greater than 100 Hz 最小 To a maximum frequency F less than 5000Hz 最大 The excitation chirp or sweep signal s(n) is a signal that generates an excitation chirp or sweep signal. In a preferred embodiment, the excitation sweep signal s(n) is a logarithmic or linear sinusoidal sweep signal. In step 210, the signal s(n) is converted into an analog signal s(t) via the D / A conversion board 13 and then sent from the control processing device 11 to the speaker 4.

[0111] In step 220, the first microphone 9 and the second microphone 10 respectively output a first electrical signal r1(t) and a second electrical signal r2(t) that vary with time, which directly measure the first sound pressure p1(t) and the second sound pressure p2(t) at points x1 and x2. p2(t). In step 230, the control processing device 11 acquires the first and second electrical signals r1(t) and r2(t) through the sound acquisition board 14, and converts them into corresponding discrete values r1(n) and r2(n) through the A / D conversion board 15, where n ∈ [1; N].

[0112] The A / D conversion board 15 is synchronized with the D / A conversion board 13, so that the electrical signals r1(t) and r2(t) are aligned in time, that is, they are acquired synchronously with the excitation signal s(t). In other words, the acquisition of the electrical signals must start exactly at the moment when the excitation signal is emitted.

[0113] The number N of discrete values depends on the measurement sampling, that is, on the time resolution of the acquisition, and thus on the excitation chirp or swept-frequency signal s(N) synthesized in step 200.

[0114] In step 240, the control processing device 11 calculates the impulse response of the ear canal 6 according to Equation 8, and obtains the first impulse response and the second impulse response

[0115]

[0116] In step 250, the control processing device 11 processes these impulse responses and and calculates the acoustic pressure impulse response of the air particles at the measurement point x0 and the velocity impulse response according to Equation 5 and Equation 6 respectively and the velocity impulse response

[0117]

[0118] The "au" above the pressure and velocity impulse responses indicates that they are quantities expressed in arbitrary units [a.u.].

[0119] Then, in step 260, the control processing device 11 converts the pressure and velocity impulse responses into physical units, multiplying them by the calibration constants α and β respectively, so as to represent them on the corresponding physical scales of [Pa] and [m / s]:

[0120]

[0121] The calibration constants α and β are obtained by methods known in the literature, see for example Stanzial D., Graffigna C.E., Protocollo di calibrazione in ampiezza e fase per sonde pressione-velocità in un campo di riferimento a onde piane progressive, Associazione Italiana di Acustica, 44° Convegno Nazionale, Pavia, 7-9 giugno 2017 ISBN: 978-88-88942-54-4, where the velocity signal is the velocity signal reconstructed from the pressure signal of the microphone. In other words, both the signal p(x0) and the signal v(x0) are reconstructed and calibrated from the signals p(x1) and p2(x2). In another embodiment of the present invention, the calibration constants α and β are provided by the microphone probe manufacturer.

[0122] In step 270, once the pressure and velocity impulse responses are converted to physical units, i.e., by applying the fast Fourier transform to them by the control processing device 11 to obtain the spectra of the pressure and velocity impulse responses and

[0123]

[0124] where ω m is the discrete frequency, where m ∈ [1; N / 2], the circumflex accent ^ indicates that the said spectrum is complex. The asterisk * above indicates that they are the spectra of the impulse responses of the measured signals, i.e., the said spectra are uncalibrated. This is because microphones usually have different responses at different frequencies.

[0125] Then, in step 280, the control processing device 11 calculates the uncalibrated admittance i.e., the cross-spectrum of the sound pressure impulse response spectrum and the sound velocity impulse response spectrum and the auto-spectrum of the sound pressure impulse response spectrum ratio:

[0126]

[0127] Finally, in step 290, the calibrated admittance measurement value of the ear canal 6 is obtained by the control processing device 11 as follows:

[0128]

[0129] where Γ(ω m) is the frequency calibration curve obtained according to the amplitude and phase calibration protocol of the pressure - velocity probe in the plane - wave reference field established by the present inventor (Stanzial D., Graffigna C.E., Funzione dicalibrazione in ampiezza e fase per sonde pressione - velocità ottenuta incampi di riferimento reattivi, Associazione Italiana di Acustica, 45° Convegno Nazionale, Aosta, 20 - 22 giugno 2018 ISBN: 978 - 88 - 88942 - 56 - 8), where the velocity signal is the velocity signal reconstructed from the pressure signal of the microphone probe.

[0130] The calibration curve Γ(ω m ) takes into account the different responses of the microphone probe when the frequency changes. In another embodiment of the present invention, the calibration function Γ(ω m ) is provided by the microphone probe manufacturer.

[0131] In step 295, the admittance spectrum is optionally displayed at the output on the screen 16

[0132] in terms of amplitude and phase. All typical tympanometric parameters, such as tympanic stiffness, ear canal volume, can be evaluated through acoustic admittance

[0133] In other words, the parameters for audiological clinical studies are calculated based on the resonance curves obtained from the admittance measured in the ear canal.

[0134] In an embodiment of the method of the present invention, where the microphone probe 8 includes a plurality of more than two microphone probes with different distances Δx iJ from each other, the above - mentioned steps are performed for each combination of microphone pairs. Then, the frequency - admittance curves are re - organized for each processed frequency band.

[0135] Since the proper coupling of the impedance probe 2 with the ear canal 6 is very important, at normal pressure, the air volume V 探针 of the impedance probe 2 and the air volume V 耳道 inside the ear canal 6 总, Optionally perform a preliminary procedure to confirm the correct coupling of the probe to the ear canal. This preliminary procedure is based on the identification of admittance resonance. Once the resonance is identified, a more accurate admittance measurement can be performed to obtain clinical audiometric parameters while maintaining the impedance probe in coupling with the ear canal where resonance occurs.

[0136] This preliminary procedure includes performing the following method: wherein the impedance probe (1) (e.g., by the operator) is coupled to the patient's ear canal (6) in a first coupling configuration (Q1), wherein a fast sweep signal s 快 (t), wherein less than 1 second, optionally equal to approximately half a second. Perform the above steps of the method to obtain a first calibrated admittance of the ear canal 6

[0137] Check whether the resonance condition of the admittance is satisfied, that is, whether the peak of the admittance module corresponds to the zero crossing of its phase.

[0138] If the resonance condition appears, the first coupling configuration (Q1) corresponds to the correct coupling of the probe to the ear canal, and the procedure ends.

[0139] Then perform the method, maintaining the first coupling configuration (Q1), and send a slow sweep signal s(t), that is, T 扫频 less than 10 seconds and greater than or equal to 1 second, for measuring the calibrated Thereby obtain the audiometric parameters of the ear canal.

[0140] If the resonance condition does not appear, iterate the method with a second coupling configuration (Q2) different from the previous one (Q1), for example, the operator changes the relative position of the probe and the ear canal, and uses the fast sweep signal s 快 (t) to obtain a second calibrated admittance and iterate the check.

[0141] In other words, the resonance of the admittance spectrum means that the position of the impedance probe relative to the ear is correct, and more accurate measurements can be performed to determine the admittance.

[0142] In a preferred embodiment of the method, if the resonance condition is verified, the control processing device 11 alarms the operator, for example, by emitting a sound signal or by sending a signal on the screen, so that the coupling configuration where resonance occurs can be maintained when performing the final measurement. The preferred embodiments of the present invention have been described, but it must be understood that those skilled in the art can make other changes and alterations without departing from the scope of protection defined by the appended claims.

Claims

1. A method for measuring the admittance of the ear canal (6) for clinical audiometry research, the method comprising at least one or more iterations of a procedure, wherein each iteration is associated with a corresponding coupling configuration (Q, Q1, Q2) between an impedance probe (1) and the ear canal (6), and wherein the procedure comprises the following steps: A. Coupling a calibrated sealed impedance probe (1) having a known air volume V 探针 to the ear canal (6) through its first end (3) such that: - The air volume V sealed inside the impedance probe (1) 探针 and the air volume V inside the ear canal (6) 耳道 constitute the total air volume V 总 , and - The longitudinal axis of the impedance probe (1) substantially coincides with the longitudinal axis of the ear canal (6); B. Sending a broadband excitation sound signal s(t) into the ear canal (6) through a loudspeaker (4) of the impedance probe (1), the loudspeaker (4) being located at a second end (5) of the impedance probe (1) opposite to a first end (3); C. By means of a microphone array (8) included in the impedance probe (1) and outputting electrical signals r1(t) and r2(t), the sound pressures p1(t), p2(t) returning from the ear canal (6) are directly detected at at least two points x1 and x2 respectively located on the longitudinal axis of the impedance probe (1) and spaced apart by a distance Δx 12 ; D. Obtain and discretize the output electrical signals r1(t) and r2(t) from the microphone array (8), respectively obtaining the discretized signals r1(n) and r2(n), where n ∈ [1; N]. E. Calculate the first impulse response through the following equation and the second impulse response where s′(t) is the time-reversed broadband sound signal s(t), FFT is the fast Fourier transform, and IFFT is the inverse fast Fourier transform; F. Calculate the impulse responses of the acoustic pressure p1(t) and p2(t) of the air particles at the measurement point x0 along the longitudinal axis of the impedance probe (1) and the velocity impulse response The measurement point x0 is the central point between points x1 and x2; G. As shown below, multiply the impulse responses of pressure and velocity by the calibration constants α and β known a priori, respectively, to convert the impulse responses of pressure and velocity into physical units of pressure and velocity: H. As shown below, the spectra of the pressure and velocity impulse responses are calculated separately by fast Fourier transform where ω m is the discrete frequency, where m ∈ [1; N / 2]; I. Calculating admittance It is the cross-spectrum of the sound pressure impulse response spectrum and the sound velocity impulse response spectrum and the auto-spectrum of the sound pressure impulse response spectrum The ratio is as follows: L. According to the following formula, the calibrated spectrum of admittance is obtained through a priori known calibration function Γ(ω m ) The steps D to L are performed by a control processing device (11).

2. The method according to claim 1, wherein the calibration constants α and β and the calibration function Γ(ω m ) are provided by the microphone manufacturer.

3. The method according to claim 1 or 2, wherein the broadband excitation sound signal s(t) is a swept-frequency signal, optionally a linear or logarithmic sine signal, within a time T 扫频 less than 10 seconds, from a minimum frequency F greater than 100 Hz 最小 changing to a maximum frequency F less than 5000 Hz 最大 .

4. The method according to claim 3, wherein the time T 扫频 is equal to 2 seconds.

5. The method according to claim 3, wherein the time T 扫频 is equal to 1 second.

6. The method according to claim 1 or 2, wherein the distance Δx 12 is equal to 12 mm.

7. The method according to claim 3, wherein step B comprises sub-steps: B1 Synthesizing (200) a digital swept-frequency signal s(n) by a generating unit (12), B2 Converting (210) the digital swept-frequency signal s(n) into a broadband excitation sound signal s(t) and inputting it into the loudspeaker (4) through a D / A conversion board (13).

8. The method according to claim 7, wherein step D is performed by an A / D conversion board (15) synchronized with the D / A conversion board (13).

9. The method according to claim 1 or 2, wherein the calibrated spectrum of the admittance is further input to a display (16) for display (295).

10. The method according to claim 1 or 2, wherein the impedance probe (1) and the ear canal (6) Coupled to the first coupling configuration (Q1), the broadband excitation sound signal s(t) is a fast sweep signal s that varies in frequency over a time less than 1 second 快 (t) to obtain a first calibrated admittance and the program further includes an additional step: M. Check whether the resonance condition in the calibration admittance is satisfied such that the peak of the module of the first calibration admittance corresponds to the zero crossing of its phase, and wherein: - If the resonance condition does not occur, another iteration of the described procedure including steps A to M is performed, where the impedance probe (1) and the ear canal (6) are coupled in another coupling configuration (Q2) different from the previous coupling configuration (Q1), and the broadband excitation sound signal s(t) is a fast sweep signal s 快 (t); - If a resonance condition occurs, steps B to L of the program are executed, where the coupling configuration is the configuration in which the resonance condition occurs, the broadband excitation acoustic signal s(t) is a swept-frequency signal whose frequency varies within a time greater than that of the fast swept-frequency signal s 快 (t), and one or more iterations of the program end. ​ 11. A clinical audiometry research method, comprising the method for measuring the admittance of the ear canal (6) according to any one of claims 1 to 10, wherein the research is performed in the coupling configuration (Q, Q1, Q2) of the last one or more iterations, and wherein the frequency of the broadband excitation sound signal s(t) varies over a time greater than or equal to 1 second.

12. An apparatus (100) for performing the method for measuring the admittance of the ear canal (6) according to any one of claims 1 to 9, comprising: - An impedance probe (1) configured to be coupled to the ear canal (6), having - A box-shaped body (2) having a first end (3) configured to be coupled to the ear canal (6), - A loudspeaker (4), near a second end (5) of the box-shaped body (2) opposite to the first end (3), is configured to emit a broadband excitation sound signal s(t), and the box-shaped body (2) is sealed and contains normal-pressure air with a volume V 探针 of normal atmospheric pressure, - A microphone array (8) accommodated in a box-shaped body (2) and configured to detect signals returning from the ear canal (6), the microphone array (8) including at least a first microphone (9) and at least a second microphone (10), with a distance Δx between them 12 and depending on the frequency of the broadband excitation acoustic signal s(t), each microphone is configured to directly detect the returning acoustic pressure p(x, t) varying with time t and output an electrical signal r(x, t); - A control processing device (11) configured to control and process input and output signals of the impedance probe (1) and perform steps B to L, having: - A generating unit (12) configured to generate a digital signal s(n) and send it to the loudspeaker (4) through a D / A conversion board (13 detachably coupled to the loudspeaker (4)), and - A sound acquisition board (14) configured to acquire an output signal from a microphone array (8) through an A / D conversion board (15) detachably coupled to the microphone array (8), The impedance probe (1) and the control processing device (11) are detachably coupled to each other.

13. The apparatus (100) according to claim 12, for performing the method for measuring the admittance of the ear canal (6) according to claim 10, wherein the control processing device (11) is further configured to perform step M.

14. The device (100) according to claim 12 or 13, wherein the box-shaped body (2) is a hollow cylinder.

15. The device (100) according to claim 12 or 13 above, the device being configured to input a broadband excitation sound signal s(t) with a frequency ranging from 100 Hz to 5000 Hz, wherein the distance Δx 12 is equal to 12 mm.

16. The device (100) according to claim 12 or 13, wherein the second end (5) is equipped with an adapter (7), the adapter (7) being configured to be easily coupled to the ear canal (6), and optionally the adapter (7) is detachable.

17. The device (100) according to claim 16, wherein the adapter (7) is frustoconical and is optionally made of rubber latex.

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