METHOD FOR AUTOMATIC DETERMINATION OF AN INDIVIDUAL FUNCTION OF A DPOAE LEVEL MAPPING OF A HUMAN OR ANIMAL HEARING

Description

[0001] The present invention relates to a method for automatically determining an individual function of a DPOAE level map of a human or animal ear according to claim 1, and to a system for carrying out this method according to the dependent claim. The present invention relates in particular to a method comprising individual features of claim 1, and to a system for carrying out this method comprising individual features of the dependent claim.

[0002] The auditory system can be viewed as a chain of successive signal processing blocks. These blocks are traversed before the more complex perception of hearing arises in the cortex. The first blocks of the signal processing chain are the outer ear (auricle and ear canal), the middle ear (ossicles with the footplate forming the boundary to the fluids of the inner ear), and the fluid-filled inner ear. The vast majority of hearing loss originates in the inner ear. This includes age-related hearing loss, which on average leads to a 25 dB hearing loss in women and 35 dB in men between the ages of 60 and 70 in the frequency range above 4 kHz. It is primarily caused by an impairment of the so-called cochlear amplifier, which, in a healthy state, amplifies incoming sound waves by a factor of 300–1000 before they are converted into neural signals by the inner hair cells and their synapses.

[0003] Since around 1980, the existence of the cochlear amplifier has been gradually proven, with David T. Kemp's discovery of otoacoustic emissions (OAEs) playing a central role in this. These are sounds that are generated as a byproduct by the active amplifier and transmitted backward through the middle ear to the ear canal. There, they can be measured with sensitive miniature microphones.

[0004] One form of OAE is distortion product otoacoustic emissions (DPOAE), in which typically two primary tones with the frequencies f 1 and f 2 and the levels L 1 and L2 will be presented. The nonlinear characteristic of the mechanoelectric transduction of the ion channels of the outer hair cells, which constitute the main motor element of the cochlear amplifier in humans and mammals in general, leads to numerous distortion products. The most easily measurable distortion product, and therefore the one preferred in diagnostic applications, is that of f dp = 2 f 1 - f 2 with f 2 > f 1 and an optimal frequency ratio of approximately f 2 f 1 = 1 , 2 Nowadays, DPOAEs are usually stimulated in such a way that, at the cochlear imaging site of the second primary tone, both excitation frequencies lead to vibration amplitudes of the basilar membrane that are as equal as possible, and accordingly, diagnostic conclusions are drawn from DPOAE findings at the frequency and according to the excitation level of the second primary tone. f 2 , L2} interpreted. DPOAE measurements can be performed and interpreted at various frequencies, for example, according to the procedure described in DE 102014108663.

[0005] A well-known method for determining the hearing threshold, or more precisely the threshold of the cochlear amplifier of the inner ear, is based on determining the threshold above which an emission, in particular a distortion product otoacoustic emission (DPOAE), is measurable, a technique that was first used in humans [BP Kimberley and DA Nelson., J. Otolaryngol., 18(7): 365-369, 12 1989; DA Nelson and BP Kimberley, J.Speech Hear.Res., 35(5):1142-1159, 10 1992].

[0006] For this purpose, a growth function is usually measured, e.g., the emissions with excitation levels of L2 = 60 dB SPL decreasing in 5 dB steps until a certain SNR (signal-to-noise ratio) is no longer achieved. The excitation level at which the required SNR is just barely reached is then referred to as the DPOAE threshold.

[0007] According to Boege and Janssen [P. Boege and T. Janssen, J. Acoust. Soc. Am., 111(4): 1810-1818, 04, 2002], the values ​​of the growth function are plotted semilogarithmically, that is, the DPOAEs are plotted linearly as sound pressure in units of [µPa] on the ordinate, against the excitation sound pressure of the second primary tone. L 2 in the logarithmic unit of [dB SPL].

[0008] With so-called optimal excitation sound pressures [P. Kummer, T. Janssen, P. Hulin, and W. Arnold. Optimal L1-L2 primary tone level separation remains independent of test frequency in humans. Hear. Res., 146(1-2):47-56, 08 2000], a linear growth function is typically obtained, which can be extrapolated to the abscissa using linear regression. In this case, the extrapolated intersection point of the growth function and the abscissa is referred to as the estimated DPOAE threshold (also: "estimated distortion product threshold", EDPT).

[0009] In general, this DPOAE threshold correlates well with psychoacoustically measured thresholds [P. Boege and T. Janssen, J. Acoust. Soc. Am., 111(4): 1810-1818, 04, 2002, MP Gorga et al., J. Acoust. Soc. Am., 113(6): 3275-3284, 06, 2003.], but exhibits an unsatisfactory high standard deviation and in individual cases a deviation of up to 40 dB [N. Schmuziger et al., J. Acoust. Soc. Am., 119(4): 1937-1939, 04, 2006]. This is partly due to the fact that interference between the two source contributions, which leads to the so-called DPOAE fine structure when measuring conventional, continuously presented DPOAEs, causes measurement errors that lead to serious misestimations, especially in the extrapolation method [E. Dalhoff, A. Vetesnik, D. Turcanu, and AW Gummer. Sound and velocity DPOAE: Technology, methodology and perspectives. HNO, 58(6):543-555, 06 2010].To separate the two interfering source contributions, various methods can be used, including pulsed DPOAE [D. Zelle, AW Gummer, and E. Dalhoff. Extraction of otoacoustic distortion product sources using pulse basis functions. J. Acoust. Soc. Am., 134(1):EL64-EL69, 07 2013]. Another reason for miscalculations is that the optimal excitation levels vary individually.

[0010] In [ML Whitehead, BB Stagner, MJ McCoy, BL Lonsbury-martin, GK Martin. Dependence of distortion-product otoacoustic emissions on primary levels in normal and impaired ears. II. Asymmetry in L1, L2 space. The Journal of the Acoustical Society of America, 97(4), 1995] the relationship between L1 / L2 levels and DPOAE is investigated.

[0011] Investigations by the applicants using pulsed DPOAEs have shown that the excitation level parameters optimal for a study population deviate significantly from the individually optimal excitation parameters in individual cases, with the following undesirable side effects: 1) DPOAEs with significantly lower amplitudes are measured, which in the usual implementations of automated measurement procedures leads to a longer measurement time in order to achieve the required SNR; 2) the globally optimal excitation path (global optimal: determined as the group mean) is such that in individual cases it leads to a significant distortion of the growth function and thus to an error in the extrapolation, which is based on the assumption of a linear function.

[0012] It is an object of the present invention to provide a method that is improved over the prior art and that incorporates the individual parameters of human or animal hearing. Ease of use is also desirable. This object is achieved by a method for automatically determining an individual function of a DPOAE level map according to claim 1.

[0013] The method according to the invention can be used for conventional, i.e., quasi-continuously measured DPOAEs. Preferably, it is combined with a method that suppresses artifacts due to the interference of two different source contributions of a DPOAE, such as a method with pulsed DPOAEs according to DE 102014108663 A1.

[0014] The inventive method for automatically determining an individual function of a DPOAE level map avoids errors in the extrapolation of the growth functions, which are inherent in the methods for measuring the distortion product threshold according to the prior art described above.

[0015] Furthermore, additional data is obtained compared to known methods, which can then be used for diagnosis. Besides the distortion product threshold... L edpt In addition to the slope of the growth function, the inventive method also acquires data on the frequency resolution and compression of the underlying traveling waves and the sound transmission loss. The general advantage of the new method is therefore that, with the same or even less time required for the measurement points, four pieces of information are obtained instead of the two required in the prior art, and that estimation errors in the previously obtained parameters (the distortion product threshold) are eliminated. L edpt and the slope of the growth function).

[0016] In an advantageous further development of the invention, the first level pair has L 1 1 L 2 1 a level L 1 of 67 ± 10 dB and a level L 2 out of 57 ± 10 dB. These levels of L 1 and of LLevel 2 has proven to be particularly favorable starting levels. For individuals with normal hearing, these excitation levels are still within the range up to which the level map rises approximately linearly, and even with hearing loss up to about 40 dB, a DPOAE can still be measured at these levels. Therefore, in most cases, values ​​are obtained that are valid for recording the level map.

[0017] The model function defines a linearly rising ridge to which linearly linked L 1 G L 2 G Level pairs are assigned (where "G" is the index for "assigned to the ridge"). According to the invention, at least half of the measured level pairs are located L 1 i L 2 i by at least 5 dB on both sides away from the area assigned to the ridge L 1 G L 2 G Level pairs (where "i" is the index of the measurement from 1 to n).

[0018] In a further advantageous embodiment of the invention, the different level pairs are L 1 i L 2 i The data is presented in a sequence that is identical for each individual. While this highly simplified and standardized (rigid) procedure makes the approximation of the individual function of a level chart somewhat less precise, it is very fast in its execution.

[0019] It can also be advantageous if the predefined, different level pairs { L 1 , L 2} are presented in a sequence that has a number of k subsequences whose level pairs { L 1 , L 2} essentially perpendicular to the linearly linked level pairs assigned to the ridge L 1 G L 2 G The inclusion of subsequences allows the ridge to be sampled at multiple points, increasing the accuracy of determining the individual function of the DPOAE level map.

[0020] In a favorable further development of the invention n≥ 5 and ≤ 12, preferably 6 ≤ n ≤ 8. The small number of planned measurements results in a short measurement duration while simultaneously ensuring good recording of the individual function of the DPOAE level map.

[0021] The number of subsequences is advantageous. k ≥ 2 and ≤ 5, which ensures good sampling of the ridge of the DPOAE level map.

[0022] It is also advantageous if the first predefined level pair L 1 1 L 2 1 subsequent level pairs L 1 2 … n k , L 2 2 … n k a subsequence with n k Measurements via a function L 1 i , L 2 i = L 1 i − 1 + μ ⋅ Δ L 1 , L 2 i − 1 + μ ⋅ Δ L 2 from the preceding pair of levels L 1 i − 1 , L 2 i − 1 to be determined, whereby µ = ± 1, in particular +1, and Δ L 1 , Δ L 2 a level difference between two consecutive level pairs and values ​​of Δ L 1 = 4 to 14 dB, preferably from 6 to 10 dB, and Δ L 2 = 0 to -2.78 dB, preferably Δ L2 = -1.52 to -2.78 dB. The factor µ This sets the search direction (towards smaller or larger) L 1 (Measuring levels) fixed across the ridge.

[0023] In a favorable further development of the procedure, when the first pair of levels L 1 1 L 2 1 and the second pair of levels L 1 2 L 2 2 two DPOAEs p dp,I (1...2)< produced, which have a signal-to-noise ratio of >=4 dB, preferably >=10 dB, the level of a subsequent third level pair L 1 3 , L 2 3 at least by Δ L 1 ≥ 4 dB set differently than the level of the previous level pair. L 1 2 L 2 2 , if p dp,I (2)< - p dp,I (1)< > 0, and on the other hand, the level of a subsequent pair of levels becomes L 1 3 , L 2 3 at least by Δ L 1 ≤ - 4 dB set differently than the level of the first level pair. L 1 1 L 2 1 , if p dp,I (2)< - p dp,I (1)< ≤ 0. This procedure ensures that at least one point to the left and one point to the right of the ridge are measured, and in between, a point is measured near the ridge.

[0024] In an advantageous further development of the procedure, when the first pair of levels L 1 1 , L 2 1 no DPOAE with p dp,I (1)< produced, which have a signal-to-noise ratio of >=4 dB, preferably >=10 dB, continue in the same search direction until either the maximum or minimum excitation level is reached. L 1 i is reached, or a group of three valid DPOAEs with p dp,I ( i..i +2)< produced, which have a signal-to-noise ratio of >=4 dB, preferably >=10 dB. This ensures, compared to a rigid method, that the ridge is also detected when it is significantly away from the position expected by normal hearing, as can be the case with conductive hearing loss.

[0025] In an advantageous further development of the procedure, if in the first subsequence after measurement at i If no group of three valid DPOAEs is produced from excitation level pairs, each exhibiting a signal-to-noise ratio of >=4 dB, preferably >=10 dB, a further subsequence with a higher level pair is produced. L 1 i + 1 L 2 i + 1 started, with the starting level pair for the renewed subsequence set to L 2 i + 3 = L 2 1 + 20 ± 10 dB , L 1 i + 3 = L 1 1 + 20 ± 10 dB The level is adjusted. It is preferably limited to the maximum technically achievable or practical level. This maximum level could, for example, be 75-85 dB SPL sound pressure. This approach allows even highly unusual individual level maps and their functions to be determined.

[0026] In an advantageous embodiment of the method according to the invention, after the DPOAE of at least 3 level pairs has been detected L 1 1 .. 3 , L 2 1 .. 3 , which are preferably assigned to a subsequence, from these 3 level pairs L 1 1 .. 3 , L 2 1 .. 3 the location of the ridge L 1 G , L 2 G determined along the line formed by the 3 pairs of levels and subsequently a fourth pair of levels L 1 4 , L 2 4 presented, which lies at a specified distance down the ridge, where the group mean of the ridge direction, φ is used, and whereby the four presented level pairs are used. L 1 1 .. 4 , L 2 1 .. 4 A slope m of the linear ridge of the level map is determined for a specific DPOAE.

[0027] Preferably, if a group of three valid DPOAEs is found in the first or second subsequence, p dp,I ( i -2... i )< is produced, which have a signal-to-noise ratio of >=4 dB, preferably >=10 dB, by automatically adapting a suitable calculation function to the associated DPOAE. p dp,I ( i -2... i )< the gauge pair below the ridge L 1 G , L 2 G = L 1 i − 2 + ε ⋅ Δ L 1 , L 2 i − 2 + ε ⋅ Δ L 2 determined, whereby ε is calculated so that p dp , I L 1 G , L 2 G a maximum is formed, and from there a fourth pair of levels is generated. L 1 i + 1 , L 2 i + 1 is presented with a function L 1 i + 1 , L 2 i + 1 = L 1 i + Δ L 1 , L 2 i + Δ L 2 , where Δ L 2 = -15 ± 10 dB is set, and the level pair is preferably set on the projection of the expected ridge onto the L1,L2 plane, i.e. with ΔL1 / ΔL2 ≈ 0.51 ± 0.15, and wherein, based on the four level pairs presented L 1 i − 2 … i + 1 , L 2 i − 2 … i + 1 The slope m of the approximately linear ridge of the level map is determined using specific DPOAE.

[0028] Based on the determined slope m of the linear ridge of the gauge map, at least two, preferably three, further pairs of gauges can be determined. L 1 i + 1 … i + 3 , L 2 i + 1 … i + 3 automatically defined, whose excitation levels are formed in a subsequence, and which are determined based on the already known position and slope of the ridge in such a way that valid DPOAEs can be expected within a measurement time of each t m ≤ 40 s to measure, for which a model function is adapted to the preferably four already validly measured DPOAEs, and then in the model function the last two or three level pairs are determined such that the expected DPOAE levels preferably at p dp , I i + 1 … i + 3 , p dp , I i + 1 … i + 3 ≥ 10 μPa lay.

[0029] Preferably, the level pairs are L 1 1 − n , L 2 1 − n The data is presented in a pulsed manner, with each individual pulse having a duration (TD) of 2 to 40 ms. Using such a pulsed presentation allows the influence of the two source contributions of a DPOAE to be suppressed or separated.

[0030] In an advantageous further development of the procedure, the level pairs are L 1 1 .. n , L 2 1 .. n in blocks of several pairs of levels presented sequentially in pulses L 1 1 .. n , L 2 1 .. n presented, with temporally directly successive level pairs L 1 1 .. n , L 2 1 .. n different excitation frequencies { f 2 , f1} exhibit. In a block, a first pulsed level pair is thus followed by { f 2.1 , f 1,1} a second level pair with different frequencies { f 2.2 f 1,2} and possibly more with { f 2, m , f 1, m}, where the frequency ratio is always close to f 2, m / f 1, m The value of 1.2 is maintained. Several blocks with time-frequency entangled pulse pairs can be averaged before evaluation. This makes it possible to use the time during which the pulse response decays after a presentation at one frequency pair to measure at another frequency, thus reducing the measurement time compared to a purely sequential approach with respect to the desired measurement frequencies.

[0031] Advantageously, in a single process step, the determined individual function of a DPOAE level chart and its parameters are stored by the computer unit in non-volatile memory. The raw data obtained can also be stored by the computer unit in this non-volatile memory. The stored data can then be used by the computer unit to continuously expand the dataset underlying the model function of the level chart.

[0032] The task is also solved by a system for carrying out the procedure, the system comprising: a computing unit, a working memory, a non-volatile memory for storing a model function p dp,M = f(L1,L2) and model parameters of the model function, at least one audio output device controlled by the computer unit for presenting tones to an individual, and at least one audio recording device connected to the computer unit for capturing DPOAEs from the individual's ear. An advantage of the new system is that, with the same or even less time required for the measurements, four pieces of information are obtained instead of the two required in the prior art, and that estimation errors in the previously obtained parameters (the distortion product threshold) are eliminated. L edpt and the slope of the growth function).

[0033] It is advantageous that at least one sound output device has a loudspeaker with a highly linear characteristic, which allows for the simultaneous playback of two tones. f 1 , f 2 No distortion occurs and one loudspeaker is sufficient for the presentation of both tones.

[0034] Advantageously, an output device is provided for displaying the individual function of a DPOAE level card, such as a display unit, monitor, display or a printer or an interface for data transmission to an external display unit, monitor, display or printer, etc., via which a determined individual function of a DPOAE level card of a human or animal ear and its parameters can be output by the system and made accessible to a user.

[0035] Furthermore, it is advantageous to provide non-volatile memory for storing the determined individual function of a DPOAE level card and its parameters.

[0036] The invention is explained in more detail in the following figures using exemplary embodiments. They show: Figure 1: A system for automatically determining an individual function of a DPOAE level map; Figure 2: A model function whose three-dimensional graph corresponds to a model level map; Figure 3: Steps according to the invention of a method for automatically determining an individual function of a DPOAE level map; Figure 4: A detailing of the step according to the method according to marking IV in Figur 3 .

[0037] In Figur 1 A system for the automatic determination of an individual function of a DPOAE level map of a human or animal ear is shown in a possible embodiment according to the invention. The system 1 comprises a probe unit 20, in particular an OAE probe, which can be positioned on an ear, and a computer unit 10. The probe unit has a probe tip 24 that can be inserted into the ear canal. A sound recording device 23, such as a microphone, is arranged in the probe unit 20 and is configured to record sounds coming from the ear canal. The probe unit 20 also provides a first and a second sound output device 21 and 22, which function as an f1 sound generator (sound output device 21) and as an f2 sound generator (sound output device 22), respectively. The sound output devices 21 and 22 can, for example, be designed as loudspeakers. It is also possible to have only one sound output device.Only one loudspeaker is provided, which is for playing two tones simultaneously. f 1 , f 2 The probe unit 20 is configured and, in particular, possesses a highly linear characteristic. The probe unit 20 is connected, for example, via a cable connection 2 to the control unit, which includes the computer unit 10. The cable connection 2 preferably contains shielded lines 3, 4, 5, through which the audio output means 21, 22 and the audio recording means 23 are connected to an AD / DA converter unit 12 of the control unit. The AD / DA converter unit 12 is, in turn, connected to the computer unit 10 via at least one line 6 for bidirectional data exchange. Alternatively, instead of the cable connection 2, the probe unit 20 could also communicate wirelessly with the control unit or with the computer unit 10. The wireless connection could, for example, be a Bluetooth radio link or another suitable radio connection, preferably with a short range.

[0038] The computer unit 10 has a working memory 15 and a non-volatile memory 16 in which a model function p dp,M = f ( L 1 , L2) for a model level map of a human or animal ear and the parameters belonging to this model function are stored. The instructions for carrying out a method according to the invention are also stored in the non-volatile memory 16. The system 1 further has an output device 11 or a display unit, such as a display, a monitor or the like, via which a determined individual function of a DPOAE level map of a human or animal ear and its parameters can be output by the system 1 and made accessible to a user. The output device 11 can also be implemented in the form of an interface via which an external output device, such as a printer or a monitor, can be connected to the system.

[0039] To perform an automatic measurement process for creating an individual function of a DPOAE level map of a human or animal ear, the probe unit 23 is inserted in the direction of arrow 40 into the ear canal 31 of an ear 30 (in Fig. 1 (indicated) introduced. The method according to the invention is described below with reference to the Figuren 3 and 4 explained.

[0040] First, however, in Figur 2 An example model function is shown, whose three-dimensional graph corresponds to a model level map. The example model function is based on the measurement data of p ≥ 2, in this case p = 6, normal hearing individuals with N ≥ 40, in this case N= 47, measured different level pairs L 1 1 … N , L 2 1 … N at excitation frequencies f₂ = 2 kHz and f₁ = 1.67 kHz. The excitation frequencies f₂ and f₁ of a level pair { L 1 , LThe two elements are preferably linked via a frequency ratio f₂ / f₁ = 1.2. A specific distortion product was evaluated, which preferably lies at the frequency f dp = 2f₁ - f₂. The superscript indices in parentheses denote the first to the Nth measurement point.

[0041] The model function defines an approximately linearly rising ridge 73, to which approximately linearly linked L 1 G , L 2 G Level pairs are assigned. Lines perpendicular to the ridge can be determined by the relationship L 2 + aL 1 = C can be defined, where C is any constant, and where a the slope parameter of the projection of the ridge onto the { L 1 , L2}-plane. In mathematical terms, the position of the ridge is defined by a successive set of gradient vectors of the scalar field formed by the DPOAE, with all other field lines formed by gradient vectors converging on and pivoting towards this ridge. The {} is shown below the model level map, shifted by p dp = 100 µPa for clarity. L 1 , L 2}-Level 71 is the transformed L 1 ′ , L 2 ′ -coordinate system 72 is drawn, which is determined by shifting the origin to { L 1 ,edpt , L 2 ,edpt } and rotation by arctan(a), as well as contour lines of the level map at 20 µPa intervals. The L 2 ′ -axis corresponds to the projection of the ridge of the level map onto the { L 1 , L 2}-level. The L 1 ′ The x-axis intersects the model hill, which approximates the level map, orthogonally. This intersection of the hill, perpendicular to the ridge, is approximated by a second-order parabola whose spread is given by a parameter c, and which enters the following equation: L dp ′ = − c L 1 ′ 2 + L dp ′ G with L dp ′ G = 20 log 10 m L 2 ′ L dp ′ and L dp ′ G where is the level of any DPOAE located on the ridge and m is the slope of the ridge along the L 2 ′ -Axis.

[0042] The L 1 ′ L 2 ′ - The coordinate system is located in the area of ​​the known coordinate system { L 1 , L 2} the area spanned by the primary tone level. The coordinate transformation mentioned above can be expressed, for example, as follows: L 1 ′ = L 1 − L 1 , edpt cos φ − L 2 − L 2 , edpt sin φ L 2 ′ = L 1 − L 1 , edpt sin φ + L 2 − L 2 , edpt cos φ

[0043] The projection of the ridge corresponds to this. L dp -hills onto the { L 1 , L 2}-level of the L 2 ′ - axis. Furthermore, the point corresponds to { L 2 ,edpt , L 1 ,edpt } the foot of the ridge of the L dp -hill, and φ is the angle between the L 2-axis and the projection of the ridge of the L dp -hills onto the { L 1 , L 2}-level, given by the one already mentioned L 2 ′ -axis. The angle φp is therefore the angle by which the L 2 ′ -axis opposite L The 2-axis is rotated. The foot of the ridge can be interpreted in a broader sense as equivalent to, but not identical with, the "estimated distortion product level" (edpt) as known from [P. Boege and T. Janssen., J. Acoust. Soc. Am., 111(4): 1810-1818, 2002].

[0044] The model function for the level map can be more positive for the area of ​​validity L dp can be described by five free parameters: a ; b; c; L 2 , edpt ′ ; mTherefore, at least 5 DPOAE are needed to calculate this area from measured values.

[0045] The method according to the invention is based on adapting the three-dimensional model function to a coarsely sampled three-dimensional DPOAE level map with preferably at least 5 measurements. In a first embodiment of the method according to the invention for automatically determining an individual function of a DPOAE level map with p dp = f ( L 1 , L 2) of a human or animal ear are transferred to the ear of an individual from the Figur 1 visible system n predefined, e.g. n = 6 predefined, excitation level pairs { L 1 , L 2} 51, 52, 53, 54, 55, 56 presented. These six predefined excitation level pairs { L 1 , L 2} 51, 52, 53, 54, 55, 56 are examples in Figur 2 in the { L 1 , L2}-level marked. From these 6 predefined excitation level pairs { L 1 , L 2} 51, 52, 53, 54, 55, 56, which are presented in two subsequences 57, 58, are then determined DPOAEs which are used via the inventive method to determine the individual function of a DPOAE level card.

[0046] According to Figur 3 In a first step 110 of the method according to the invention, the model function already described is first read from the non-volatile memory 16 into the computer unit 10 of the system 1, or into the main memory 15 of the computer unit 10. After the model function has been read, a number of different level pairs are read by the system 1 in a second step 120. L 1 1 … n , L 2 1 … n of an excitation frequency pair { f 1 , f2} output via the sound output means 21, 22 of the probe unit 20 or presented to an individual and the corresponding DPOAEs of the individual are recorded via the sound recording means 23, wherein at least the first level pair L 1 1 L 2 1 is predefined and where n << Nist. The corresponding DPOAEs are fed to the computer unit 10 for further processing via the AD / DA converter unit 12. The superscript indices in parentheses denote the 1st to nth measurement point.

[0047] In a first variant of the method according to the invention, which can be referred to as the adaptive variant, the second step 120 comprises a series of sub-steps 121 to 127, which are described below with reference to Figur 4 will be explained in more detail.

[0048] According to Figur 4 In the first substep 121 of the second step 120, a starting level is initially set. L 1 1 L 2 1 (preferably a level L 1 of 67 ± 10 dB and a levelL 2 of 57 ± 10 dB) for a first level pair from the non-volatile memory 16 into the computing unit 10. Furthermore, in this substep 121 the step sizes Δ L 1 , Δ L 2 for the other level pairs L 1 2 … n L 2 2 .. n as well as thresholds for search direction decisions L dp , min G 1 The SNR min value is read into computer unit 10. SNR min represents the desired SNR (signal-to-noise ratio). L dp , min G 1 This denotes the DPOAE level on the ridge that must be present along at least one of the k subsequences so that a subsequent subsequence below the first can still be expected to have a sufficient SNR. If this value is not reached, the next subsequence above the first, i.e., up the ridge, is sampled to avoid an excessively long measurement time required to achieve a sufficient SNR. The step sizes Δ L 1 , Δ L2 denotes the level difference between two consecutive level pairs, where Δ L 1 in particular a value of Δ L 1 = 4 to 14 dB, preferably from 6 to 10 dB, and wherein Δ L 2 = 0 to -2.78 dB, preferably Δ L 2 = -1.52 to -2.78 dB.

[0049] In a second substep 122 of the second step, the measurements of the first subsequence are now carried out. k Subsequences perpendicular to the presumed degree of individual function of a level map. The DPOAEs are performed at the excitation frequencies f₂ = 2 kHz and f₁ = 1.67 kHz already described above. The excitation frequencies f₂ and f₁ of a level pair {L₁, L₂} are preferably linked via a frequency ratio of approximately f₂ / f₁ = 1.2. The subsequence belongs to a number k subsequences, where k The number of subsequences is ≥2 and ≤5. Each subsequence contains a number of n subsequences. k Level pairs {L 1 ,L 2} measured.

[0050] The starting level L 1 1 L 2 1 will be done according to the specified step sizes ΔL 1 , Δ L 2 varies according to the formula L 1 n + 1 = L 1 n + Δ L 1 ′ cos φ and the further formula L 2 n + 1 = L 2 n − Δ L 1 ′ sin φ If a descending or no rising edge is measured in the measured subsequence, the search direction is reversed and Δ L 1 ' = - Δ L 1 '

[0051] In a third substep 123, it is checked whether at least three valid DPOAEs were measured. If this check is positive, meaning that three valid DPOAEs were measured, the procedure continues to the next substep 124. If no three valid DPOAEs were measured, the measurement is repeated, in which a new excitation level L1(1)<, L2(1)< is calculated from the original excitation level L1(1)<, L2(1)<. L 2 1 = L 2 alt + ΔL 2 ′ cos φ , L 1 1 = L 1 alt + ΔL 2 ′ sin φ is determined.

[0052] In the following fourth substep 124, the position of the ridge of the individual function is determined using the three validly determined measured values, e.g. by solving a parabolic equation and finding the individual maximum according to the function: L dp ′ G 1 = f L 1 1 .. 3 L 2 1 .. 3

[0053] Here means L dp ′ G 1 that point on the estimated ridge of the individual model function, whose associated excitation level pair on the by L 1 1 .. 3 L 2 1 .. 3 the formed line. The position of the ridge of the individual function at the higher excitation levels L (1..3)< is therefore already known from substep 124, but the slope of the ridge, i.e. the parameter m, is not.

[0054] In the subsequent fifth substep 125 of the second step 120, a second subsequence is measured along the presumed ridge, whereby only one measurement is obtained. The measurement is carried out according to the formula L 1 4 = L dp ′ G 1 − Δ L 2 ′ sin φ .

[0055] falls below L dp ′ G 1 a preset limit ( L dp , min ′ G 1 ), this step is performed towards higher levels (Δ L 2 = - Δ L 2).

[0056] The measured value of DPOAE ( L dp 4 ) is subsequently used in the sixth substep 126 to determine the individual slope of the ridge, m.

[0057] In the sixth substep 126 of the second step 120, the individual slope of the ridge is calculated according to the formula m = f ( L dp (G,1)< , L 1 (G,1)< , L 2 (G,1)< , G dp (4)< , L 1 (4)< , L 2 (4)< ). Based on the determined slope m of the ridge, a starting level L 1 (5)< , is now determined. L 2 (5)< for the third subsequence.

[0058] In the seventh substep 127 of the second step 120, the measurements of the third subsequence are now carried out across the presumed ridge of the function: A variation of Δ L 1 ′ in L 1 n + 1 = L 1 n + Δ L 1 ′ cos φ .

[0059] Preferably, at least half of the level pairs are located { L 1 , L 2}, where measurements are taken to ensure a minimum of 5 dB on both sides away from the group assigned to the ridge (the model function). L 1 G L 2 G Level pairs.

[0060] Using the measured values ​​obtained according to the second step 120 and its substeps 121 to 127, the previously presented model function is now adapted to the acquired measured values ​​in a third step 130 in the computer unit 10. Here, the three-dimensional model function is applied to the measured DPOAE values. p dp,M = f ( L 1 , L 2) adjusted. The adjustment is performed using mathematical methods of least squares adjustment, e.g., the method of least squares, i.e., by iteratively minimizing the difference between the n measured values ​​and the values ​​of the model function. p dp,M = f ( L 1 , L 2) to the measured n DPOAE (corresponding to the associatedL 1 , L 2 coordinates) until an individual function is obtained p dp,I = f ( L 1 , L 2) with individual parameters of a DPOAE function and level map of the individual by the computer unit 10. This allows for the simple creation of an individual function / level map of an individual's hearing with greatly reduced measurement effort in a short time.

[0061] In a fourth step 140, the individually adapted function and its function parameters are now output to an output device 11 of the system 1, such as a display, monitor, printer, etc. The output function parameters include, in particular, the parameters already described above. a ; b; c; L 2 , edpt ′ ; and the slope of the ridge m. The output device 11 can, as already mentioned, also be implemented in the form of an interface via which an external output device, such as a printer or a monitor, can be connected to the system 1.

[0062] In a possible further process step, the determined individual function of a DPOAE level chart and its parameters can be stored by the computer unit 10 in the non-volatile memory 16. The measured raw data can also be stored by the computer unit 10 in the non-volatile memory 16. The stored data can be used by the computer unit 10, for example, for the continuous expansion of the data set underlying the model function of a level chart.

[0063] The following insights can be gained from the individually adapted function obtained according to the invention and the associated functional parameters: An approximate distortion product threshold can be calculated, providing information about the threshold of the input signal for the inner hair cells of the measured ear. The corresponding parameter can be... L 2,edpt The width of the ridge, described in the function by the parameter c, is a measure of the compression and thus of the frequency resolution of the underlying traveling waves in the measured ear. The position and angle, expressed in the function by the parameters a ; b contains information about the nature of a hearing loss: In the case of pure conductive hearing loss, the angle (expressed in the function by the parameter a) does not change; instead, to a first approximation, the ridge shifts to the same extent in the direction of higher L 1 - and L2 -level. If, for example, the shift of the hill (compared to the standard values, or to a reference measurement of the individual at an earlier time) coincides with the deterioration of the distortion product threshold, i.e., Δ L 2 ≈ ΔL 1 ≈ Δ L 2 ,edpt A purely conductive hearing loss can be inferred. The steepness of the slope, expressed by the parameter m, allows conclusions to be drawn about a possible conductive hearing loss. As long as the hearing loss is below 30 dB, it can be expected that in the case of purely conductive hearing loss, the slope will correspond to the normal values, while a deviation from the normal value indicates a proportional reduction in retrograde middle ear transmission. f dp It is indexed.

[0064] In an alternative embodiment of the method according to the invention, instead of sub-steps 121 to 127, a number of nfixed or predefined but different level pairs { L 1 , L 2} (where n is preferably ≥5 and ≤ 12, in particular ≥ 5 and ≤ 8) output by the system and the response of an individual's hearing to these level pairs { L 1 , L 2} recorded. This variant can be described as a rigid method. The level pairs { L 1 , L 2} can in turn be in a number k Subsequences (57, 58; cf. Fig. 2 ) are measured, whereby k ≥2 and ≤12. The n level pairs are then largely static, and there is no adjustment of the second and, if applicable, third subsequence to the results of the measurements of the first subsequence, as is the case with the previously described method. The number n of level pairs { L 1 , L2} is designed according to a trade-off between measurement time (as few measurement points as possible) and achievable accuracy (as many points as possible).

[0065] In this rigid method with fixed excitation levels, for example, with L 2 ′ = 40 dB for the three higher excitation levels, and L 2 ′ = 25 dB for the three lower excitation levels, and within a group of three excitation levels each L 1 ′ = 0 ± 6 dB be measured. In the { L 1 , L 2} -coordinate system corresponds to the excitation levels L 2 = 68.1; 65.6; 63.1; 42.8; 45.3; 40.3 and L 1 = 68.0; 73.5; 79.0; 63.3; 57.8; 68.7 (see also Fig. 2 The election pursues the following goals: L 1 ′ = 0 ± 6 dB The goal is to accurately measure the position of the ridge using three points that lie perpendicular to its presumed location: at f 2 = 2 kHz, the DPOAE falls with Δ L 1 ′ ± 6 dB The standard setting typically drops to about 50% of the maximum value. If the primary target is individuals with normal hearing, as is usually the case with screening tests, the standardized setup will yield good results. However, outliers must be identified. This is possible using the root mean square error of the model fit. If the error is too high, i.e., if the root mean square error (rms) is, for example, greater than 5 µPa, Further level pairs must be measured until the error is low enough. Here, further [approaches] are possible. Δ L 1 ′ - Steps are taken. The same procedure must be followed if individual measurement points cannot be registered due to an insufficient signal-to-noise ratio.

[0066] Finally, it should be noted that, in contrast to the frequency ratio used and described above, f 2 / f In addition to 1 of 1.2, a different frequency ratio can also be chosen. For example, the frequency ratio can be... f 2 / f1 z. It could also be set to another suitable value between 1.15 and 1.35. Furthermore, the frequency ratio could be... f 2 / f 1 be a function of f2. Bezugszeichenliste

[0067] 1 System 2 Cable connection 3 First line 4 Second line 5 Third line 6 Fourth line 10 Computer unit 11 Output device 12 A / D / A converter unit 13 A / D converter 14 A / D converter 15 Working memory 16 Non-volatile memory with stored model function 20 Probe unit, OAE probe 21 First sound output device, f1 sound transducer 22 Second sound output device, f2 sound transducer 23 Sound recording device, microphone 24 Probe tip 30 Ear 31 Ear canal 40 Arrow 51 Excitation level pair { L 1 , L 2} 52Excitation level pair { L 1 , L 2} 53Excitation level pair { L 1 , L 2} 54Excitation level pair { L 1 , L2} 55Excitation level pair { L 1 , L 2} 56Excitation level pair { L 1 , L 2} 57 first subsequence 58 second / further subsequence 70Graph / Model level map 71{ L 1 , L 2}-level 72 transformed L 1 ′ L 2 ′ -Coordinate system 73 degrees (of the DPOAE model level map) 110 first process step 120 second process step 121 first sub-step 122 second sub-step 123 third sub-step 124 fourth sub-step 125 fifth sub-step 126 sixth sub-step 127 seventh sub-step 130 third process step 140 fourth process step

Claims

1. Method for the automated determination of an individual function of a DPOAE level map with pdp,I = f(L1, L2) of human or animal hearing, wherein distortion product otoacoustic emissions (DPOAEs) are presented as acoustic pressure p in dependence on levels L1 and L2 of the two primary tones used for the generation of DPOAEs, characterized in that it comprises the following steps: - reading (110) of a model function (70) pdp,M = f(L1, L2) with model parameters of a DPOAE level map, based upon a number of N DPOAE measurements of a stimulation frequency pair f1, f2 with respectively different level pairs {L1(1...N), L2(1...N)} in a population (p) of normally hearing subjects into a main memory (15) of a computer unit (10), wherein N ≥ 40 and p ≥ 2, - automatically presenting (120) n different level pairs {L1(1...n), L2(1...n)} of a stimulation frequency pair f1, f2 via tone output means (21, 22) to an individual and detecting the corresponding DPOAEs of the individual via tone recording means (23), wherein at least the first level pair {L1(1), L2(1)} is predefined, and wherein n << N, - iteratively adapting (130) the model function pdp,M = f(L1, L2) to the measured n DPOAEs until an individual function pdp,I = f(L1, L2) is obtained with individual parameters of a DPOAE level map of the individual by the computer unit (10), and - outputting (140) the individual function pdp,I = f(L1, L2) and / or its individual parameters to an output means (11) of the computer unit (10), wherein the method is characterized in that the model function has a more or less linearly rising ridge (73) to which more or less linearly linked level pairs {L1(G), L2(G)} are assigned, wherein at least half of the measured level pairs {L1, L2} lie at least 5 dB remote from either side of the group of the level pairs {L1(G), L2(G)} assigned to the ridge (73).

2. Method according to claim 1, characterized in that the first level pair {L1(1), L2(1)} has a level L1(1) of 67 ± 10 dB and a level L2(1) of 57 ± 10 dB.

3. Method according to any one of the above claims, characterized in that the different level pairs {L1, L2} are presented in a sequence that is identical for each individual.

4. Method according to any one of the above claims, characterized in that the predefined, different level pairs {L1, L2} are presented in a sequence that has a number of k subsequences whose level pairs {L1, L2} are essentially transverse to the linearly linked level pairs {L1(G), L2(G)} assigned to the ridge.

5. Method according to any one of the above claims, characterized in that n is ≥ 5 and ≤ 12, and preferably n is ≥ 5 and ≤ 8.

6. Method according to any one of the above claims, characterized in that k ≥ 2 and ≤ 8.

7. Method according to any one of the above claims, characterized in that the level pairs {f1(2...nk), L2(2..nk)} of a subsequence following a first predefined level pair {L1(1), L2(1)} is determined with nk measurements by a function {L1(i), L2(i)} = {L1(i-1)+ µ · ΔL1, L2(i-1) + µ · ΔL2} from the respectively preceding level pair {L1(i-1), L2(i-1)}, wherein µ = ±1, preferably +1, and ΔL1, ΔL2 is a level distance of two sequential level pairs and has values of ΔL1 = 4 to 14 dB, preferably from 6 to 10 dB - and ΔL2 = 0 to -2.78 dB , preferably ΔL2 = -1.52 to -2.78 dB.

8. Method according to any one of the above claims, characterized in that, when the first level pair {L1(1), L2(1)} and the second level pair {L1(2), L2(2)} produce two DPOAEs with pdp,I(12) that each have a signal-to-noise ratio of >= 4 dB, preferably >= 10 dB, the level of a subsequent third level pair {L1(3), L2(3)} is adjusted to differ by at least ΔL1 ≥4 dB from the level of the preceding level pair {L1(2), L2(2)} when pap,I(2) - pdp,I(1) > 0; on the other hand, the level of a subsequent level pair {L1(3), L2(3)} is adjusted to differ by at least ΔL1 ≤ -4 dB from the level of the first level pair {L1(1), L2(1)}, when pdp,I(2) - pdp,I(1) ≤ 0.

9. Method according to any one of the above claims, characterized in that, when the first level pair {L1(1), L2(1)} does not produce any DPOAEs with pdp,I(1) that have a signal-to-noise ratio of ≥ 4 dB, preferably ≥ 10 dB, the same search direction is continued until either the maximum or minimum stimulation level L1(i) is reached, or a group of three valid DPOAEs with pdp,I(i..i+2) was produced that have each a signal-to-noise ratio of ≥ 4 dB , preferably ≥ 10dB.

10. Method according to any one of the above claims, characterized in that, when a group of three valid DPOAEs that have a signal-to-noise ratio of ≥4 dB, and preferably ≥10 dB is not produced in the first subsequence, another subsequence is started with a higher level pair {L1(i+1), L2(i+1)}, wherein the start level pair for the new subsequence is set to L2(i+3) = L2(1) + 20 ± 10 dB, L1(i+3) = L1(1) + 20 ± 10 dB, or at most to the maximum achievable level.

11. Method according to any one of the above claims, characterized in that, after detecting the DPOAEs of at least 3 level pairs {L1(1..3), L2(1..3)}, preferably of one subsequence, the position of the ridge {L1(G), L2(G)} along the line formed by the three level pairs is determined from these three level pairs {L1(1..3), L2(1..3)}, and a fourth level pair {L1(4), L2(4)} is presented that is placed at a predetermined distance down the ridge, wherein the group average of the ridge direction ϕ is used, and wherein a slope of the linear ridge of the level map is calculated using the DPOAEs determined from the four presented level pairs {L1(1..4), L2(1..4)).

12. Method according to claim 1 or 11, characterized in that, when a group of three valid DPOAEs with pdp,Ii-2..i is produced in the first or second subsequence that each have a signal-to-noise ratio of >=4 dB, preferably >=10 dB, the level pair below the ridge {L1(G), L2(G)} = L1(i-2) + ε · ΔL1, L2(i-2) + ε · ΔL2} is determined by adapting a mathematical function to the associated DPOAEs pdp,I i-2...i, wherein ε must be calculated so that pdp,I(L1(G), L2(G)) forms a maximum, and on that basis a fourth level pair L1(i+1), L2(i+1) is presented, with a function {L1(i+1), L2(i+1)} = {L1(i) + ΔL1, L2(i) + ΔL2}, wherein ΔL2 = -15 ± 10 dB is adjusted, and the level pair is preferably adjusted to the projection of the anticipated ridge on the L1, L2 level, i.e., adjusted with ΔL1 / ΔL2 ≈ 0.51 ± 0.15, and wherein a slope m of the approximately linear ridge of the level map is determined using the DPOAE calculated from the four presented level pairs L1(i-2...i+1), L2(i-2...i+1).

13. Method according to any one of the above claims, characterized in that the level pairs {L1(1..n), L2(1..n)} are presented as pulsed, wherein each individual pulse is presented with a duration TD of 2 to 40 ms.

14. Method according to claim 13, characterized in that the level pairs {L1(1..n), L2(1..n)} are presented within a measuring block consisting of a plurality of level pairs {L1(1..n,m), L2(1..n,m)} which are presented sequentially over time in pulses, wherein level pairs {L1(1..n,i), L2(1..n,i)}; {L1(1..n,i+1), L2(1..n,i+1)} that follow each other directly in time have different stimulation frequencies {f2,i,f1,i}; {f2,i+1, f1,i+1}, wherein, in particular, in an additional method step, the determined individual function of a DPOAE level map and its parameters are stored by the computer unit (10) in a non-volatile memory (16).

15. A system configured for performing the method according to any one of the above claims 1 to 14, with a computer unit (10), a main memory (15), a non-volatile memory (16) for storing a model function pdp, M = f(L1, L2) and model parameters of the model function, at least one tone output means (21, 22) controlled by the computer unit (10) for presenting tones to an individual, with at least one tone recording means (23) connected to the computer unit (10) for detecting DPOAEs from the ear of the individual, wherein in particular the at least one tone output means (21, 22) is a speaker with a highly linear characteristic and / or wherein in particular an output means (11) is provided for outputting the individual function of a DPOAE level map to a user.