METHOD AND DEVICE FOR EXAMINATION OF HEARING ABILITY

Description

[0001] The invention relates to a method based on the measurement of distortion products of otoacoustic emissions (DPOAE). The method according to the invention is used in particular for the objective and quantitative determination of sound processing in a mammalian ear and thus for the examination and subsequent evaluation of hearing ability. According to EP 2 053 877 A1 and DE 199 05 743 A1, the measurement results can also be used for the adjustment of hearing aids. The method is based on a special excitation pattern that allows conclusions to be drawn about the operating point of the cochlear amplifier.

[0002] In particular, the present invention relates to a method for detecting distortion products of otoacoustic emissions (DPOAE) in a hearing organ, comprising the steps of: (a) outputting at least one first primary tone pair each comprising a first primary tone with frequency f 1.1 and sound pressure level L1.1 and a second primary tone with frequency f 2.1 and sound pressure level L 2.1 with f 2.1 > f 1,1 , and (b) detecting evoked distortion products of otoacoustic emissions (DPOAE), characterized in that the first primary tone { f 1.1 , L 1,1} with a time delay t was after the second primary tone { f 2.1 , L 2,1} is output.

[0003] The auditory system can be viewed as a chain of successive signal processing blocks. These are passed through before the more complex perception of hearing arises in the cortex. The first blocks in the signal processing chain are the outer ear (pinna and auditory canal), the middle ear (the auditory ossicles with the footplate as the boundary to the fluids of the inner ear), and the fluid-filled inner ear. The vast majority of hearing losses occur in the inner ear. This includes age-related hearing loss, which, on average, leads to 25 dB hearing loss in women and 35 dB in men in the frequency range above 4 kHz at the age of 60-70. This is dominated 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.

[0004] Since around 1980, the existence of the cochlear amplifier has been successively demonstrated, with David T. Kemp's discovery of otoacoustic emissions (OAE) playing a central role. These are sounds generated as a byproduct of the active amplifier and transmitted through the middle ear back to the ear canal, where they can be measured with sensitive miniature microphones.

[0005] One form of OAE is the distortion product otoacoustic emissions (DPOAE), which usually result from the simultaneous presentation of two primary tones with the frequencies f 1 and f 2 and the (sound pressure) levels L 1 and L2. The nonlinear characteristics of the mechanoelectric transduction of the ion channels of the outer hair cells, which represent 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 preferred in diagnostic applications is the one at 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 .

[0006] With a suitable choice of stimulus parameters (preferably f 2 f 1 = 1 , 2 and L 1 ≥ L 2 ) the traveling waves triggered by the primary tones overlap in the cochlea in an area basal to the characteristic imaging location of the frequency f 2 . Nowadays, DPOAEs are usually excited in such a way that at the cochlear imaging location 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 corresponding to the excitation level of the second primary tone { f 2 , L 2}. DPOAE measurements can be performed and interpreted at different frequencies, for example, using the method described in DE 102014108663.

[0007] Typically, the amplitude of the DPOAE is extracted from the spectrum of the measured signal using a Fourier transform. Since DPOAEs have a very low sound pressure level, which can be significantly below the hearing threshold, averaging must be performed for a sufficiently long time to obtain a certain signal-to-noise ratio and thus a reliable diagnostic result. If multiple DPOAEs are measured at a single frequency,f 2 and different sound pressure levels L 2 and combined into a so-called growth function, a more precise statement about the function of the cochlear amplifier in the inner ear is obtained. For each excitation frequency f 2, the so-called threshold value can then be determined based on the growth curve, below which the lowest level L 2, at which the DPOAE still reaches a given minimum signal-to-noise ratio. This threshold cannot be measured because the measured noise is finite; it must be determined by extrapolation.

[0008] In order to obtain a diagnostic statement over the entire frequency range, typically 6 to 8 growth functions are measured sequentially.

[0009] The growth curves determined in this way and the threshold values ​​extrapolated from them can then serve as a basis for improved diagnostics and for the adjustment of hearing aids, because the extrapolated threshold values ​​can be seen as a direct statement about the hearing loss.

[0010] The DPOAE generation process and the measurement and evaluation methods used to date are also described in Dalhoff et al., "Schall- und Geschwindigkeits-DPOAE," in HNO 2010, 58: 543-555. Further references are also found there, to which explicit reference is made.

[0011] The DPOAE can be stimulated by both continuous and pulsed tones. As mentioned previously, continuous tones are those that are presented for such a long time that their spectrum is sharp.

[0012] In pulsed DPOAE, at least one of the two primary tones (typically the second primary tone { f 2 , L 2}) is fed in pulsed, while the other primary tone (typically the first primary tone { f 1 , L 1}) is also presented pulsed or as a continuous tone. The ratio of L 2 to L 1 is first set in a specific area, then L 2 gradually changed. According to the general Fourier relationship between the time and frequency domains, the "pulsed (primary) tones" are tones whose spectrum is broadened due to the shortness of the pulse. If one of the tones, such as the aforementioned first primary tone { f 1 , L 1} is presented as a continuous tone, this means that the pulsed second primary tone { f 2 , L 2} while the first primary tone is stopped { f 1 , L 1} undergoes an on and off process. Conversely, the second primary tone { f 2 , L 2} are presented as a continuous tone, while the pulsed first primary tone { f 1 , L 1} while the second primary tone is being held { f 2 , L 2} goes through a switching on and off process.

[0013] Methods of pulsed DPOAE are described, among others, in Dalhoff et al., "Two-source interference as the major reason for auditory-threshold estimation error based on DPOAE input-output functions in normal-hearing subjects", in Hearing Research 296 (2013), pages 67 - 82. Another method of pulsed DPOAE with pulse interleaving is disclosed in WO 2015 / 192969 A1.

[0014] In the method described in WO 2015 / 102969 A1, a first pulsed primary tone { f 1.1 , L 1,1} and a second pulsed primary tone { f 2.1 , L 2.1} applied, whereby the f 1 -Pulse before f 2 pulse starts, and after the f 2 pulse ends, ie the f 1 pulse is longer than the f2 pulse of a pulse pair. WO 2015 / 102969 A1 refers to short pulses of approximately 1 - 10 ms, the duration of which corresponds approximately to the latency between stimulation and the manifestation of the first nonlinear distortion contribution of a DPOAE on the basilar membrane in the inner ear. In an alternative embodiment described in WO 2015 / 102969 A1, two short pulses of equal or similar length are presented by f 1 -Pulse after the f 2 pulse is used. To save time, these two short pulses are coordinated so that both pulses are applied simultaneously to the f 2 -image location in the inner ear.

[0015] All known DPOAE methods (including the pulsed DPOAE described above) are used to diagnose the amplification performance of the cochlear amplifier, which, with the outer hair cells (OHCs) as a key element, is responsible for mechanical, preneural amplification of the input signal, and thus also determines the hearing threshold up to a hearing loss of approximately 50 to 60 dB (D. Zelle, E. Dalhoff, and AW Gummer, "Objective Hearing Diagnostics with DPOAEs. New Insights into Generation and Clinical Application," HNO, vol. 64, no. 11, pp. 822-830, 2016). However, it has not been possible to determine the cause of a loss of amplification using these methods, in particular, whether this is due to a loss of intact OHCs or rather an impairment of the energy supply by the Stria vascularis (i.e. ultimately a reduction in the endocochlear potential).

[0016] This is where the method developed according to the invention comes in, which has the task of providing a DPOAE method that improves the known DPOAE methods and that can, in particular, provide information about the cause of a loss of amplification.

[0017] According to the invention, this object is achieved in the method mentioned at the outset in that a pair of two primary tones, each with an excitation frequency f 1 or f 2 is presented, with the second primary tone { f 2 , L 2} , which is stimulated with significantly lower sound pressure according to the usual excitation paradigms, is presented first, while the first primary tone { f 1 , L 1} with a time delay it's late opposite the second primary tone { f 2 , L 2} is presented.

[0018] The first primary tone is defined by a first excitation frequency f 1 and a first sound pressure levelL 1 . It is also known as " f 1 primary tone". The second primary tone is defined by a first excitation frequency f 2 and a first sound pressure level L 2 . It is also known as " f 2 primary tone". If in the following a "first primary tone { f 1 , L 1} " or a " f 1 primary tone", the corresponding statements basically refer to both the first primary tone of the first primary tone pair of the method according to the invention (ie the first primary tone { f 1.1 , L 1,1}) , as well as to each further first primary tone of an n-th (further) primary tone pair (ie the first primary tone { f 1,n , L 1,n}). Analogously, the term "second primary tone { f 2 , L 2} " or " f 1 -primary tone" basically the second primary tone { f 2.1 , L2,1}, as well as every further second primary tone of an n-th (further) primary tone pair (ie the second primary tone { f 2,n , L 2,n}).

[0019] The time delay t was until the first primary tone was fed in { f 1 , L 1} typically depends on the latencies of the two traveling waves involved. Latency functions for the nonlinear source are described in D. Zelle, AW Gummer, and E. Dalhoff, "Latencies of Extracted Distortion-Product Otoacoustic Source Components," in Mechanics of Hearing: Protein to Perception, vol. 1703, KD Karavitaki and DP Corey, Eds.: AIP conference proceedings, 2014.

[0020] Preferably t was at least 0.5 milliseconds (ms), ie the first, preferably pulsed, primary tone { f 1 , L 1} is preferably at least 0.5 ms after the second primary tone { f 2 , L 2} is switched on. In principle,t lag can be chosen as large as desired, but it can be advantageous to increase the time delay t lag as short as possible in order not to extend the measurement time unnecessarily. t lag is preferably less than or equal to 10 ms, less than or equal to 7.5 ms or particularly preferably less than or equal to 5 ms. Preferably t was selected from the range between 10 ms and 0 ms, particularly preferably from the range between 5 ms and 0.5 ms.

[0021] In the method according to the invention, the first primary tone { f 1.1 , L 1,1} preferably presented pulsed (ie as " f 1 pulse"). As stated above, "pulsed" primary tones are tones which, according to the general Fourier relationship between time and frequency domain, have a broadened spectrum due to the shortness of the pulse. Furthermore, the second primary tone { f 2.1 , L2,1} pulsed (ie as " f 2 -pulse") or as a continuous tone. "Pulsed" primary tones undergo an on-and-off process during the measurement period and are typically presented for a duration of 50 ms or less. In the method according to the invention, the second primary tone { f 2.1 , L 2,1} as a continuous tone or pulsed (" f 2 pulse"), while the first primary tone { f 1.1 , L 1,1} is preferably fed in pulsed (" f 1 -Pulse"). Preferably, both primary tones are presented pulsed, with the pulse length of the second primary tone { f 2.1 , L 2,1} the pulse length of the first primary tone { f 1.1 , L 1.1} exceeds.

[0022] Furthermore, regardless of the type of presentation of the second primary tone as a continuous tone or pulse, it may be preferable that the f 1 pulse during the pause of the second primary tone {f 2.1 , L 2,1} undergoes an on and off process. If both primary tones of the primary tone pair are pulsed (in other words: as f 1 pulse or the f 2 pulse), it may be preferable that the pulse length of the f 1 pulse is shorter than the pulse length of the f 2 pulses.

[0023] Alternatively, if both primary tones are presented pulsed, the second pulsed primary tone { f 2.1 , L 2,1} are switched on first, whereas the first pulsed primary tone { f 1.1 , L 1,1} with a time delay t lag (as defined above) and still the second pulsed primary tone { f 2.1 , L2,1} is switched off. This procedure can also be considered a mixture of the PTA-I and PTA-II excitation schemes. The presentation occurs initially after switching on according to PTA-II. Preferably, DPOAE excitation according to PTA-II provides evidence of correct inner ear homeostasis. Before switching off, the presentation occurs according to PTA-I, which allows the interference state of the nonlinear and coherent reflection source to be determined.

[0024] The f 1 -Pulse of the first primary tone pair { f 1.1 , L 1.1 ; f 2.1 , L 2,1} can therefore be before or after the end of the f 2 pulses of the first primary tone pair are switched off.

[0025] In any case, the duration of the f 1 pulse and / or the duration of the f 2 -Pulse in the PTA-II stimulation scheme should be selected to be longer than the latency of the evoked DPOAE, preferably at least twice, more preferably at least three times, and most preferably at least five times as long. It may be particularly preferred to increase the duration of the f 1 pulse and / or the duration of the f 2 - Pulses in the PTA-II stimulation scheme should be selected to be five to seven times the latency of the evoked DPOAE. The latency of the evoked DPOAE depends on the selected frequency for each f 1 - and f 2 - primary tone (see Zelle et al. AIP Conference Proceedings 1703, 090023 (2016)).

[0026] The length of the first primary tone { f 1.1 , L 1,1} preferably between 40 ms and 1 ms, more preferably between 30 ms and 2 ms, even more preferably between 25 ms and 2 ms. The length of the second primary tone { f 2.1 , L2,1} is then chosen to be longer accordingly. This way, the second primary tone { f 2.1 , L 2,1} can be presented as a continuous tone or pulsed. However, depending on the selected overall stimulation pattern, the preferred pulse length may vary. Particularly for the combined PTA-I / PTA-II stimulation scheme, longer pulses of 200 ms or less, 100 ms or less, or 50 ms or less may also be considered, as described below.

[0027] The "duration" or "length" of a pulse (also called "pulse length" or "pulse width") is the so-called full half-width ( T HB or "full width half maximum" ( TFWHM). For this pulse length, the time is determined from which the cosine-shaped rising edge has risen to half of the equilibrium value ("steady-state") until the corresponding time in the switch-off edge. This pulse length results from the preferred pulse shape, according to which the pulses have a cosine-shaped rise of typically 0.1 ms to 4 ms in length, a "steady-state" with the sound pressure level L 2 or L 1 , which is typically 2 ms to 12 ms long, followed by another cosine-shaped section.

[0028] The sound pressure levels L 1 and L 2 of the at least one primary tone pair can preferably be chosen similarly, since the risk of mutual suppression can increase with increasing sound pressure level difference. If several primary tone pairs are presented in one measurement, the maximum sound pressure level difference between the L 2 -Sound pressure levels of, for example, four primary tone pairs, a fixed threshold can be defined, which can be, for example, between 5 and 15 dB.

[0029] These excitation patterns described here with a (around t lag ) delayed presentation of the (preferably pulsed) f 1 primary tone are also referred to as Primary Tone Arrangement II (PTA-II) and are in contrast to methods known in the state of the art, in which the f 1 primary tone is presented first, and the f 2 primary tone begins with a time delay. Such excitation patterns, known from the state of the art, are also referred to here as Primary Tone Arrangement I (PTA-I).

[0030] The inventors recognized that DPOAE stimulation according to PTA-I or PTA-II leads to different amplitudes (cf. Fig. 1). In particular, the response of the nonlinear source (ie the temporally first part of the envelope of the 2 f 1 - f 2 -DPOAE time signal) is larger for PTA-II than for PTA-I. This is particularly interesting because its amplitude is usually larger than that of coherent reflection sources, and in contrast, it does not depend on any additional process (namely, the presumed roughness of the impedance function). The reason for the observed deviation in the response of the nonlinear source lies in the asymmetry of the so-called mechano-electrical transduction curve of the OHCI. This transduction curve represents the dependence of the intracellular receptor potential (output) on the stimulus, e.g., the deflection of the stereocilia of the OHCI (input). The operating point, with intact cochlear homeostasis, lies approximately at the point of maximum slope of the curve (cf. simplified stimulation in Fig. 2 ).

[0031] The excitation of the nonlinear source of the DPOAE takes place near the imaging location of the second primary tone with the frequency f 2 (" f 2 imaging location"), where the traveling waves of both primary tones overlap most strongly. The decisive area for the generation of the DPOAE is the area from about ½ octave basal to the f 2 imaging location, since here the oscillators contribute maximally to the amplification of the input oscillations. f 2 imaging location, both primary tones have different latencies, since the phase transfer function of a cochlear traveling wave becomes steeper towards the imaging location. Therefore, the largest phase shift only occurs shortly before the maximum of the wave amplitude. Since the traveling wave of the first primary tone (" f 1 -traveling wave") on f 2 imaging location has not yet reached its amplitude maximum, its latency at this location is significantly lower. If both primary tones are switched on simultaneously, thef 1 -Traveling wave f 2 -image location first and already contribute to the shift of the DC potential before the second primary tone { f 2 , L 2} arrives and the DPOAE can be generated. This is the case in the PTA-I scheme.

[0032] When applying the PTA-II scheme according to the invention - where the (pulsed) second primary tone { f 2 , L 2} is switched on first and optionally switched off last - the relatively quieter f 2 -Pulse does not yet lead to any noticeable DC potential shift, so that the pulsed first primary tone { f 1 , L 1} is presented when the cochlear amplifier is still (almost) in its resting state. In a normal physiological state of the cochlea, the operating point is then close to the optimum, i.e., the highest amplification power. Thus, a higher DPOAE amplitude is obtained.

[0033] Advantageously, it can therefore be determined, in particular by comparing two measurements, i.e. a PTA-I and a PTA-II measurement at the same frequency and the same excitation levels of the two primary tones, whether the expected change in amplitude is present and therefore an optimal, non-pathological setting of the operating point of the cochlear amplifier can be assumed.

[0034] In the method according to the invention, the excitation is carried out with at least one pair of primary tones { f 1.1 , L 1,1} and { f 2.1 , L 2,1}, which are preferably both presented pulsed (ie as a "pulse pair").

[0035] The excitation frequencies f 1 and f 2 of a primary tone pair are preferably determined by a frequency ratio f 2 / f1 = 1.2. However, this frequency ratio can also be set to any other suitable value, preferably between 1.15 and 1.35. See, for example, Johnson et al., "Influence of primary-level and primary-frequency ratios on human distortion product otoacoustic emissions," in J. Acoust. Soc. Am. 119, 2006, pages 418-428.

[0036] Such primary tone pairs usually consist of a first (pulsed) and a second (optionally pulsed) primary tone { f 1 , L 1} and { f 2 , L 2}, where the frequency f 1 over a defined frequency ratio f 2. Likewise, the sound pressure level L 1 according to a predefined rule L 2. The term "primary tone pairs" includes the term "pulse pairs", which are pairs of first pulsed and second pulsed primary tone { f 1 , L 1} and { f 2 ,L 2}.

[0037] As described above, in the method according to the invention, the first and second primary tone of a primary tone pair are presented slightly offset in time, with the (preferably pulsed) second primary tone { f 2.1 , L 2,1} before the (preferably pulsed) first primary tone { f 1.1 , L 1,1} begins. If the (preferably pulsed) first primary tone ends { f 1.1 , L 1,1} before the (preferably pulsed) second primary tone, and especially when, with pulsed presentation of both primary tones, the first primary tone { f 1.1 , L 1,1} a shorter pulse length than the second primary tone { f 2.1 , L 2,1}, this excitation scheme is also called "PTA-II". Conversely, an excitation scheme in which a (preferably pulsed) first primary tone { f 1,n , L1,n} before the (preferably pulsed) second primary tone { f 2,n , L 2,n} and ends after this, especially if, with pulsed presentation of both primary tones, the second primary tone { f 2,n , L 2,n} a shorter pulse length than the first primary tone { f 1,n , L 1,n} is referred to as "PTA-I." Typical pulse lengths are listed above and are generally applicable to PTA-I and PTA-II.

[0038] It may be preferred according to the invention to adjust the length of the f 1 -Pulses beyond the latency of the nonlinear source ("extended f 1 pulse"), in order to preferably show the stimulus-induced shift of the receptor potential in a single measurement (cf. Fig. 3 ). Typical pulse lengths for extended f 1 -Pulses are preferably between 5 and 20 ms.

[0039] As described above, in the process according to the invention the f2 primary tone of a primary tone pair before the (preferably pulsed) f 1 primary tone begins, and can end, after the (pulsed) f 1 -Primary tone has been terminated, ie the f 2 -Primary tone can be longer than the (pulsed) f 1 -Primary tone of a primary tone pair. If the f 1 -Primary tone with a time delay it's late compared to the f 2 primary tone is switched on, the DPOAE preferably reaches a maximum at the beginning and then decreases before rising again (cf. Fig. 3 ). This subsequent increase can in principle be caused by the influence of the second source (reflection component), but also by slower regulatory processes of the difference between intra- and extracellular potentials, or by the dynamics of the localized positive feedback loop leading to the cochlear amplification.

[0040] When switching off the (preferably pulsed)f 1 primary tone, a recovery process takes place, which in principle can result from the restoration of the resting potential as well as from influences of the second, i.e. the coherent reflection source.

[0041] In methods known in the state of the art with excitation according to PTA-I, after switching off the (typically pulsed) f 2 primary tone, however, neither the early maximum nor the recovery process is reached. In contrast, a single measurement according to the method according to the invention can be carried out with a (preferably pulsed) f 1 primary tone can already clarify the presence of a DC potential shift. If a pathological shift in the DC potential is present, the change is expected to be significantly smaller depending on the frequency, and under certain circumstances (e.g., at low frequencies) the sign may even change.

[0042] Alternatively, in the process according to the invention, the f2 primary tone of a primary tone pair before the (preferably pulsed) f 1 primary tone begins, and can end, before the f 1 -Primary tone has been completed. In other words, the f 1 pulse after switching off the f 2 pulses.

[0043] The method according to the invention can further comprise the output of at least one further (n-th) primary tone pair each comprising a first primary tone with frequency f 1,n and sound pressure level L 1,n and a second primary tone with frequency f 2,n and sound pressure level L 2,n, where f 2,n > f 1,n . The other primary tone pair has a f 2 excitation frequency, which differs either from the f 2 -excitation frequency of the first primary tone pair (ie f 2.1 ≠ f 2,n ) or a f 2 -Excitation frequency, which the f2 excitation frequency of the first primary tone pair (ie f 2.1 = f 2,n ). The presentation of at least one additional primary tone pair can occur either before or after the presentation of the first primary tone pair. It is also possible that the presentation of the first primary tone pair is "embedded" in the input of additional primary tone pairs.

[0044] The at least one further primary tone pair can be presented according to the excitation pattern PTA-II (like the first primary tone pair) or according to the excitation pattern PTA-I. This means, (a) the second primary tone of the at least one further primary tone pair { f 2,n , L 2n} can be calculated with a time delay t was after the first primary tone { f 1,n , L 1,n} of this at least one further primary tone pair, or (b) the first primary tone of the at least one further primary tone pair { f 1,n , L1,n} can be calculated with a time delay t was after the second primary tone { f 2,n , L 2,n} of this at least one further primary tone pair can be output.

[0045] Here, n can be selected from any, preferably integer, ≥ 2. Preferably, n = 2.

[0046] Option (a) preferably corresponds to stimulation according to PTA-I. In particular, it is provided that the second primary tone and optionally the first primary tone are presented in a pulsed manner. If both primary tones are presented in a pulsed manner, the pulse length of the f 2 pulses preferably shorter than the pulse length of the f 1 pulses.

[0047] Option (b) preferably corresponds to stimulation according to PTA-II. In particular, it is provided that the first primary tone and optionally the second primary tone are presented in a pulsed manner. If both primary tones are presented in a pulsed manner, the pulse length of thef 1 pulse is preferably shorter than the pulse length of the f 2 pulses.

[0048] As described above, a combined PTA-I / PTA-II excitation scheme is particularly useful for comparing the change in the obtained amplitude of the excited DPOAE (especially of the nonlinear source). For this purpose, preferably after the inventive excitation according to the PTA-II scheme, at least one further n-th primary tone pair { f 1, n , L 1,n , f 2,n , L 2n}, where the second primary tone { f 2,n , L 2n} of at least one further n-th primary tone pair with a time delay t was after the first primary tone { f 1,n , L 1,n} of this primary tone pair is output. The output of at least one further n-th primary tone pair { f 1,n , L 1,n , f 2,n , L2n} optionally before or after the output of the first primary tone pair { f 1.1 , L 1.1 , f 2.1 , L 2,1}.

[0049] Preferably, the method according to the invention - especially when it comprises stimulation by means of PTA-I and PTA-II - can further comprise a step of comparing the signals generated by outputting the first primary tone pair {f 1,1 ,L 1,1 ,f 2,1 ,L 2,1} evoked DPOAE with those by the output of another primary tone pair {f 1,n , L 1,n , f 2,n , L 2,n} with identical sound pressure levels L and frequencies f , but with different delays between stimulus pulses.

[0050] As described above, according to the method of the invention, the first primary tone { f 1.1 , L 1,1} and / or { f 1,n , L 1 , n} ) and optionally the second primary tone { f 2.1 , L 2,1} and / or { f 2,n , L 2n} preferably pulsed, ie as "f 1 pulse" or " f 2 pulse" are presented. This applies both to stimulation according to PTA-II and to a possible additional stimulation according to PTA-I.

[0051] For the preferred excitation frequencies, sound pressure levels, pulse lengths and other parameters, the statements made with regard to PTA-II generally apply accordingly for excitation according to PTA-I.

[0052] In particular, the duration of the f 1 pulse and / or the duration of the f 2 -Pulse in the PTA-I stimulation scheme should be selected to be longer than the latency of the evoked DPOAE, preferably at least twice, more preferably at least three times, and most preferably at least five times as long. It may be particularly preferred to increase the duration of the f 1 pulse and / or the duration of the f 2 pulses in the PTA-I stimulation scheme should be selected so that they correspond to five to seven times the latency of the evoked DPOAE.

[0053] In particular, the duration of the f 1 pulse { f 1.1 , L 1,1} of the first primary tone pair and / or the f 2 pulses { f 2,n , L 2,n} of the nth further primary tone pair can be 200 ms or less, 100 ms or less, 50 ms or less, between 40 ms and 1 ms, between 30 ms and 2 ms, or between 25 ms and 5 ms. Especially for a combined PTA-I / PTA-II stimulation scheme, the pulse length can be extended to 200 ms or less, 100 ms or less, or 50 ms or less. Furthermore, the pulse length of the f 2 -pulses of the n-th further primary tone pair { f 2,n , L 2,n} should preferably be shorter than the pulse length of the f 1 -pulse of the n-th further primary tone pair { f 1,n , L 1,n}.

[0054] As explained above, the combination of a PTA-II excitation with the first primary tone pair { f 1.1 , L1.1 , f 2.1 , L 2,1} with an excitation according to PTA-I with a second primary tone pair { f 1,n , L 1,n , f 2,n , L 2,n} may be advantageous in order to compare the obtained amplitudes with each other and to draw conclusions about the setting of the operating point of the cochlear amplifier. For this purpose, the excitation frequencies and sound pressure levels are expediently chosen to be the same, and only the respective excitation scheme is changed in order to guarantee the comparability of the obtained results. In other words, the frequency and sound pressure level of the first primary tone of the first and each further n-th primary tone pair and / or the frequency and sound pressure level of the second primary tone of the first and each further n-th primary tone pair are preferably identical. In other words, the following preferably applies in the methods according to the invention: { f 1.1 , L 1,1} = { f 1,n , L 1,n} and / or {f 2.1 , L 2,1} = { f 2,n , L 2,n}, more preferably { f 1.1 , L 1,1} = { f 1,n , L 1,n} and { f 2.1 , L 2,1} = { f 2,n , L 2,n},

[0055] In summary, the achievement of the invention consists, among other things, in using an excitation scheme which is new compared to the prior art, wherein preferably (1) two different measurements according to PTA-II and PTA-I (where the above applies to the choice of excitation frequencies and sound pressure levels) or (2) a measurement according to PTA-II with extended f 1 pulse is performed.

[0056] A crucial innovation, according to option (1), is that for a given pair of primary tones, the DPOAE response is compared with respect to two different excitation modes (PTA-I and PTA-II). This option is not provided for in the state of the art. Stimulation using different excitation modes can, in principle, influence the DPOAE response in three different ways: Suppression: In the inner ear, the compressive nonlinearity of the transmission curve of mechanoelectrical transduction, characterized by the limiting states of fully open or closed ion channels, leads to the presentation of a second signal – in this case, the switching on of the respective time-delayed primary tone – leading to so-called suppression effects. This is inevitable, because DPOAEs are preferentially generated when both primary tones are simultaneously present at the f 2 -imaging location. In the inner ear, the traveling wave caused by a single primary tone is strongly dependent on an area extending approximately 1 / 3 of an octave basal to its maximum. In this area, the outer hair cells supply the traveling wave with the additional energy in phase, which leads to the cochlear amplification. Since both primary tones are chosen to f 2 -image location reach approximately the same amplitude (i.e. the f 1 -primary tone stimulates significantly more strongly, since it forms its maximum further apically), the f 1 -Primary tone with its flatter basal flank the outer hair cells in the area about 1 / 3 octave stronger than the f 2 -Primary tone (which is f 2 imaging site forms a relatively sharp maximum). Therefore, the DPOAE responses vary depending on the excitation paradigm (PTA-I or PTA-II), because the basal to the f 2 -image location in the case of initial excitation with the f 1 -Primary tone according to PTA-I is more saturated and in the generation of the following f 2 -Primary tone can no longer provide full amplification.

[0057] DC shift: DC effects are the effects of a comparatively low-frequency, transient shift of the resting potential in the outer hair cells, and thus also of the position of the basilar membrane and the tectorial membrane. Under normal physiological homeostasis in the inner ear, the operating point is relatively close to the state of completely closed ion channels (i.e., clearly asymmetric). At high amplitudes, where the input signal is clipped by both threshold states, the low-pass filtered signal component (i.e., the transient resting potential shift) should transition to the mean potential. f 1 -Primary tone according to PTA-I is switched on first, this transition to the center potential has taken place in most cells before the f 2 - primary tone is switched on and a DPOAE response could be measured. Therefore, the shift in the resting potential, which leads to a slight reduction in the gain of the outer hair cells, is not visible. In the PTA II arrangement, however, the f 2 - Primary tone first, and in the area corresponding to 1 / 3 octave basal to f 2 -image location, the resting potential shift only takes place in full once the f 2 -primary tone is switched on. This resting potential shift becomes visible in that the DPOAE response initially reaches a higher amplitude, but then decreases due to the resting potential shift. From this point on, the DPOAE responses of both excitation paradigms are almost identical, until a similar effect is observed during switching off (removal of the shifted resting potential). This also explains the striking difference between the two DPOAE curves: In the PTA II excitation scheme, the DPOAE response increases approximately 2 ms earlier than in the PTA I excitation scheme. This value corresponds to approximately 1 / 3 of the latency of the DPOAE responses for the frequency of f 2 = 2 kHz (approx. 6 ms). The later switched on f 1 -Primary tone reaches the more basal f 2 imaging site well before the DPOAE response reaches its maximum, and is at the f 2 -Imaging location is not yet clearly band-limited. Broadband signals generally lead to steeper slopes in the time domain.

[0058] Efferent innervation of the outer hair cells. In the healthy ear, a sound generates a neural stimulus that travels from the inner hair cells through the brainstem to the cortex. Interneurons in the brainstem feed the stimulus back to the outer hair cells via efferent innervation, resulting in a slight attenuation of the cochlear amplifier in the healthy ear. However, this effect typically results in an attenuation of at most 1 dB (<10% amplitude reduction). Second, the time constant of this effect is approximately 40 ms, so, based on current knowledge, it cannot account for the difference between the two pulse response forms.

[0059] If, in the method according to the invention, several primary tone pairs (according to PTA-I or PTA-II) are presented in one measurement, the application of the pulse interleaving method described below may be useful in order to shorten the measurement time. For this purpose, a set from the first primary tone pair { f 1.1 , L 1.1 ; f 2.1 , L 2,1} and at least one further primary tone pair { f 1,n , L 1,n ; f 2,n , L 2,n} is output in a block that is repeated several times during the measurement period.

[0060] Advantageously, the method according to the invention can include a further upstream step which checks at the beginning of the measurements whether the frequency fdp of one of the evoked DPOAEs interferes with a spontaneous emission (SOAE). This is particularly advantageous if several primary tone pairs are to be presented during the measurement (for example, according to the pulse interleaving method mentioned above). This allows artifacts and interference sources to be detected right at the beginning of the measurement. If this is the case, the block time can be adjusted, for example. T B or the duration T S can be adjusted for one or all slots so that the decay time of the DPOAE is extended so that its sound pressure level falls below a certain threshold before the next primary tone pair is presented. Alternatively, for example, the f 2 excitation frequency to achieve a minimum distance to the SOAE.

[0061] Preferably, for this purpose, at the beginning of a measurement for a primary tone pair with a first primary tone { f 1 , L 1} and a second primary tone { f2 , L 2} a DPOAE can be measured. In the event that no DPOAE can be measured, the sound pressure levels L 2 and L 1 incrementally until either the maximum sound pressure level that can be output L 2 or L 1 is reached or a DPOAE is measured. This simple method allows the presence of interfering SOAEs to be detected and, if necessary, compensated.

[0062] Furthermore, the method according to the invention for determining individual level maps can be combined with the level map method described below.

[0063] For effective suppression of primary tones { f 1 , L 1} and { f 2 , L 2} In addition to the usual filtering methods, the Primary-tone-phase-variation- The method of Whitehead et al., 1996, ibid., is used. In general, it is preferable to check at the beginning of the measurements whether the frequency of one of the DPOAEs ( fdp ) interferes with a spontaneous emission (SOAE). Here, it is advantageous that artifacts and interference sources are detected at the beginning of the measurement. If this is the case, the method can be adapted to extend the decay time of the DPOAE so that its level falls below a certain threshold before the next primary tone pair is presented, or to adjust the frequency f 2 is moved to maintain a minimum distance from the SOAE.

[0064] The methods according to the invention can be used to determine the amplification performance of the cochlear amplifier in a human or animal hearing organ and, advantageously, also to determine the cause of a possible loss of function. The methods according to the invention are also suitable for adjusting a hearing aid. Figures

[0065] Further advantages will become apparent from the following description of the attached figures. Figure 1Comparison of the amplitudes of the envelopes of the 2 f 1 - f 2-DPOAE after stimulation with PTA-I (grey line) and PTA-II (black line). Figure 2 Transduction curve of the AEHZ and its effect on the receptor potential for different intensities of DPOAE excitation tones. Figure 3 Measurement of the SPDPOAE or resting potential shift with a prolonged stimulation f 1 pulse (pulse length 20 ms). Figure 4 State-of-the-art PTA-I excitation scheme in which the f 2 -Pulse (black, solid line) during the sustained f 1 pulses (dashed line) is presented. Figure 5 A system for automatically determining an individual function of a DPOAE level map. Figure 6 A model function whose three-dimensional graph corresponds to a model level map. Figure 7 Procedure steps for the automatic determination of an individual function of a DPOAE level map. Figure 8Detailing of the procedural step after marking IV in Figure 7 . Figure 9 Comparison of the amplitudes of the envelopes of the 2 f 1 - f 2-DPOAE after stimulation with PTA-II (left) and PTA-I (right). Figure 10 Superimposed curves from Figure 9 .

[0066] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0067] Embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings.

[0068] Figure 1 shows the envelopes of the 2 f 1 - f2-DPOAE after stimulation with PTA-I (grey line) and PTA-II (black line). PTA-I and PTA-II lead to different amplitudes. If the f 1 -Sound switched on later than the f 2 tone (here: 5 ms later) (PTA-II), one obtains a higher amplitude of the envelope of the 2 f 1 - f 2 -DPOAE (black line), than if, conversely, the f 2 tone switches on 5 ms later than the f 1 tone (grey line) (PTA-I).

[0069] In the present example, the DPOAE response curves show only the response of the nonlinear source, while the response of the coherent reflection source is too small to be detected in this subject and at this frequency. The response of the nonlinear source is relevant because its amplitude is normally larger and, unlike the coherent reflection source, it does not depend on any additional process (roughness of the impedance function).

[0070] In this example, the response of the nonlinear source (ie, the envelope of the 2 f 1 - f 2 -DPOAE time signal) is 3 dB greater for PTA-II than for PTA-I. This difference is sufficiently large to be reliably detected.

[0071] Figure 2shows the transduction curve of the AEHZ (1) and its effect on the receptor potential for DPOAE excitation tones of varying strengths. Input is the deflection of the stereocilia, output the receptor potential, which controls the force coupling of the cell into the oscillations of the organ and thus the amplification process. Since the ion channels can only be fully closed or fully opened, the transduction curve reaches a maximum or minimum value at high input values, which in the normalization chosen here are the values ​​1 or 0, respectively. Furthermore, two input signals ((2a) and (2b)) are shown, which correspond to excitation with two primary tones. The resulting beat is clearly visible. One excitation occurs with a relatively low amplitude ((2a), solid line), which addresses a still relatively linear part of the transduction curve.Second, an excitation with a significantly higher amplitude is shown ((2b), dashed line), which is clearly processed nonlinearly. The resulting output signals are also shown. For the case of small-signal excitation ((3a) solid, thick line), the system response is visually indistinguishable from the input signal. (4) represents the mean value, i.e., the DC component of the signal. For stronger excitation (5), the influence of nonlinearity is clearly visible. Due to the asymmetry of the transduction curve, the negative half-waves of the potential fluctuations are strongly truncated, while the positive half-waves still show a somewhat sinusoidal shape. As a result, the mean value, i.e., the DC value of the potential fluctuations, shifts.

[0072] In a healthy case, the operating point shifts from the steepest point to a less steep one. This must lead to a certain reduction in the gain of the oscillation frequency. Preferably, the shift in the resting or DC potential occurs largely frequency-independently within 1-2 ms.

[0073] Figure 3 shows the measurement of the SPDPOAE or resting potential shift with a stimulation with prolonged f 1 -short pulse. If the second primary tone { f 2 , L 2} first, and the extended fIf a 1-short pulse is applied with a 5 ms delay, the DPOAE in this example initially reaches a maximum at 113 µPa, then drops by more than 3 dB within 2 ms, and then rises again. This subsequent increase can, in principle, be caused by the influence of the second source, but also by slower regulation processes of the difference between intracellular and extracellular potentials. (1) Excitation using PTA-II, (2) Excitation using PTA-I. Pulse entanglement method

[0074] The method according to the invention can also be combined with the pulse entanglement method known from WO 2015 / 192969 A1 ("time-entangled multi-frequency method").

[0075] Compared to continuous DPOAEs, pulsed DPOAEs have the disadvantage that the measurement of a frequency-sound pressure level combination generally has a low time utilization and thus a correspondingly lower signal-to-noise ratio for the same measurement time. However, the method described in WO 2015 / 192969 A1 significantly reduces this disadvantage by interleaving multiple measurements in the time-frequency domain, i.e., presenting them alternately with a time delay. This allows, for example, seven frequencies to be stimulated and analyzed within a block with a time delay. The measurement process is thus accelerated by parallel and adaptive stimulation and analysis steps, allowing the measurement of growth curves for 5-7 frequencies. f 2 in typically 2-2.5 min.

[0076] In the method described in WO 2015 / 192969 A1, at least two different pulse pairs (each with a pulsed first primary tone { f 1 , L1 } and a pulsed second primary tone {f 1 , L 1 }) with different excitation frequencies f 2 (and consequently also different excitation frequencies f 1 ) is presented in a block that is repeated several times during the measurement period. In a block, a first pulsed primary tone pair is followed by { f 2.1 , f 1,1} a second primary tone pair with different frequencies { f 2.2 , f 1,2} and if necessary further with { f 2 ,n , f 1, n} , where the frequency ratio is preferably always close to f 2, n / f 1, n = 1.2 is maintained.

[0077] WO 2015 / 192969 A1 provides that the pulsed primary tones of each pair are generated according to the PTA-I excitation scheme (with f 2 short pulse). f1 pulse of a pulse pair before the f 2 pulse and ends after the f 2 pulse has been completed, ie the f 1 -Pulse is longer than f 2 -pulse of a pulse pair.

[0078] The pulse entanglement method according to the invention provides for the presentation of at least one primary tone pair according to the PTA-II excitation scheme (with f 1 short pulse). The other primary tone pairs in a block can be presented either according to PTA-II (pure PTA-II pulse interleaving) or according to PTA-I (combined PTA-I / PTA-II pulse interleaving).

[0079] In the pulse entanglement method according to the invention, the beginning of a (PTA-I or PTA-II) pulse pair follows in a block, preferably with a time interval T ( T-SLOT or TS ) to the beginning of the immediately preceding (PTA-I or PTA-II) pulse pair in the block, where TSusually corresponds at least to the length of the previous pulse. Preferably TS > 10 ms. This measurement time, reserved for a (PTA-I or PTA-II) pulse pair in a block, is also referred to as a slot. It should be noted that slots do not overlap; rather, one slot follows the other when the previous slot is completed.

[0080] Advantageously, the second (PTA-I or PTA-II) pulse pair is only presented when the DPOAE evoked by the first (PTA-I or PTA-II) pulse pair has sufficiently decayed (to approximately 1 to 10% of the initial value), so that there are no noticeable interferences in the measurement of the sound pressure levels ( L dp ) of the individual DPOAE, which compared with the sound pressure levels L 1 and L 2 the f 1 - and f 2 -Pulses have only a very low sound pressure level. In addition, the increased time interval between the presentation of (PTA-I or PTA-II) pulse pairs with the same excitation frequencies f 1 and f 2 sufficient recovery time for the DPOAE triggered in the previous measurement block to completely subside.

[0081] Preferably, the or each block of (PTA-I or PTA-II) pulse pairs during a block time T B. The block time T B is defined as the sum of the slot lengths T S of a block. Preferably T B is preferably selected so that a (PTA-I or PTA-II) pulse has sufficiently resonated when it is repeated. Preferably, there is a time interval between the beginning of a first and a following pulse pair with the same excitation frequency f 2 a time interval of 30 ms to 100 ms, preferably at least 70 ms.

[0082] Preferably, the f 2 -Excitation frequencies of two immediately consecutive (PTA-I or PTA-II) pulse pairs in a block are at least one octave apart. The choice of such a frequency separation of at least one octave between the f 2 -Excitation frequencies advantageously ensure that the frequencies for dp the evoked DPOAEs are sufficiently far apart so that there are preferably no noticeable interferences in the measurement of the individual DPOAEs.

[0083] For the excitation frequencies f 1 and f 2 the above still applies, for example a preferred frequency ratio of f 1 / f 2 =1,2. An example of two different pulse pairs of a block is a first pulse pair with an excitation frequency f 2 of 1.5 kHz and an excitation frequency f 1 of 1.25 kHz and a second pulse pair with an excitation frequencyf 2 of 4 kHz and an excitation frequency f 1 of 3.33 kHz.

[0084] A preferred set (i.e. panel or frequency-time pattern of the excitation frequencies in a block.) of f 2 -Excitation frequencies in a block consists of the excitation frequencies f 2 = 1 kHz, f 2 = 3 kHz, f 2 = 1.5 kHz, f 2 = 6 kHz. This f 2 -Excitation frequencies are presented repeatedly in this order in a block. Another preferred set (panel) of f 2 - Excitation frequencies in a block consists of the excitation frequencies f 2 = 2 kHz, f 2 = 4 kHz, f 2 = 1.5 kHz, f 2 = 3 kHz.

[0085] The (PTA-I) f 1 -Pulse can be switched on frequency-dependent preferably 3-10 ms earlier and 3-10 ms later than the (PTA-I) f 2 -Pulse, so that the (PTA-I) f 1 -Pulse during the presentation of the (PTA-I) f 2 -Pulses briefly reach an equilibrium state.

[0086] However, to save as much time as possible, it can also be combined with two equally or similarly short (PTA-I) f 1 and f 2 pulses are used, which are time-shifted so that at the most diagnostically valuable imaging site of the (PTA-I) f 2 pulses in the cochlea, both excitations occur simultaneously. Then the (PTA-I) f 1 pulse is switched on approximately 0.1-3 ms later, since its travel time is closer to the basal (towards the footplate) imaging location of the f 2 pulses is shorter than for the (PTA-I) f 2 pulse. If this setting is optimally selected, no effect occurs through the afferent-efferent feedback loop of the medial olivocochlear reflex.

[0087] The duration (length) of the (PTA-I) f 1 and f2 pulses in a pulse pair can preferably be 2 to 20 ms. Regarding pulse length, the same applies as stated above for PTA-II.

[0088] In the pulse interleaving method of the present invention, the sequence of pulse pairs and the time interval between two consecutive (PTA-I and / or PTA-II) pulse pairs, i.e. the slot time ( T S ) must be constant in a block. In this block-fixed approach, as many blocks are measured and averaged until the desired SNR is achieved for each excitation frequency in the set (panel). Alternatively, when the desired SNR is reached for an excitation frequency, f 2 the remaining pulse pairs for this excitation frequency f 2 and consequently their averaging can be skipped. For this purpose, measurements can be continued with the remaining pulse pairs in shortened blocks, i.e., with fewer slots, which further shortens the measurement time.

[0089] Furthermore, in the pulse entanglement method according to the present invention, two sets with at least partially with respect to the second excitation frequency f Two different (PTA-I and / or PTA-II) pulse pairs are selected, with the blocks of the individual sets being presented sequentially, and the DPOAE measured and averaged. The sets are thus processed sequentially. In this block-flexible procedure with a fixed pulse arrangement, for example, seven (PTA-I and / or PTA-II) pulse pairs with different excitation frequencies are used. f 2 are arranged in such a way that, according to general experience, they are all allocated approximately the averaging time required to achieve a certain signal-to-noise ratio.

[0090] Preferably, according to the invention, several sets are presented one after the other, to which (PTA-I and / or PTA-II) pulse pairs are distributed in such a way that (PTA-I and / or PTA-II) pulse pairs with low excitation frequencies f 2 (and thus also low excitation frequencies f 1 ) appear in several sentences.

[0091] In the pulse interleaving method according to the invention, it is possible to continuously check for each (PTA-I and / or PTA-II) pulse pair whether a desired SNR is achieved. In the further measurement of the (PTA-I and / or PTA-II) pulse pairs, for this excitation frequency f 2 is eliminated and the remaining (PTA-I and / or PTA-II) pulse pairs are redistributed to the blocks if necessary.

[0092] In this block-flexible method with free (PTA-I and / or PTA-II) pulse pair arrangement, the length of the measurements for the individual (PTA-I and / or PTA-II) pulse pairs is no longer fixed relative to each other. Instead, each (PTA-I and / or PTA-II) pulse pair is continuously checked to see whether the SNR has been achieved; as soon as this is the case, a check is made to see whether another (PTA-I and / or PTA-II) pulse pair is still incomplete. In this way, the completely measured (PTA-I and / or PTA-II) pulse pairs are successively eliminated from the measurement, and only the remaining (PTA-I and / or PTA-II) pulse pairs are presented. On the one hand, it is checked whether the octave spacing between two consecutive (PTA-I and / or PTA-II) pulse pairs is maintained. If this is no longer the case, (PTA-I / PTA-II) pulse pairs may no longer be processed in the blocks to which they were originally assigned, but in other (newly defined) blocks.In addition, it is checked whether the required time interval . T (according to the time for a slot ( TS ) plus the necessary cooldown time ( T Abkl. )) between (PTA-I and / or PTA-II) pulse pairs with the same excitation frequency f 2 is complied with.

[0093] As described above with regard to PTA-II, the sound pressure levels of the (PTA-I and / or PTA-II) pulse pairs are preferably chosen to be similar within a block.

[0094] Preferably, the DPOAE is measured for all excitation frequencies contained in the set(s) f 2 at a sound pressure level assigned to the excitation frequency L 2 measured and averaged, and then at least one new measurement at new sound pressure levels L 2, wherein preferably in a threshold approximation method from the measured DPOAE for each excitation frequency f 2 the new sound pressure level L2 for each new measurement. This procedure is repeated until for each excitation frequency f 2 a growth curve from measured values ​​of the sound pressure levels of the DPOAE for 3 to 4 different sound pressure levels L 2, from which the respective threshold values ​​are then determined. A more detailed description of this method can be found in WO 2015 / 192969 A1. Level chart method

[0095] The method according to the invention can be combined with the level map method known from PCT / EP2017 / 000334. A "DPOAE level map" (DPOAE level map, cf. Shera and Guinan, J Acoust Soc Am. 2007 Feb;121(2):1003-16) and Martin et al. J. Acoust. Soc. Am. 127 5 , pp. 2955-2972) denotes the amplitude of a level (here the 2f1-f2- distortion product) depending on the primary sound levels.

[0096] The method described in PCT / EP / 2017 / 000334 is used to automatically determine an individual function of a DPOAE level map. This method preferably avoids errors in the extrapolation of growth functions that are inherent in other methods known in the state of the art for measuring the distortion product threshold. L edpt can occur due to the nature of the principle. The method described in PCT / EP2017 / 000334 can be used for conventional (i.e., quasi-continuously) measured (PTA-II excited) DPOAEs. However, it can also be combined with a pulsed (PTA-II excited) DPOAE method, as described in DE 102014108663 A1. In particular, the method described in PCT / EP2017 / 000334 can be combined with the combined pulse entanglement described above.

[0097] In particular, the methods of the present invention may include the following steps for automatically determining an individual function of a DPOAE level map with p dp,I = f ( L 1 , L 2 ) of a human or animal hearing: Reading in a model function p dp,M = f ( L 1 , L 2 ) with model parameters of a DPOAE level map, based on a number of N DPOAE measurements of an excitation frequency pair { f 1 , f 2} with different level pairs L 1 1 … N L 2 1 … N in a population ( p ) of normal hearing people, into a working memory of a computer unit, whereby N ≥ 40 and p ≥ 2, automatic presentation of n different level pairs L 1 1 … n L 2 1 … n an excitation frequency pair { f 1 , f 2} via sound output means to an individual and detecting the corresponding DPOAE of the individual via sound recording means, wherein at least the first level pair L 1 1 L 2 1 is predefined and where n << N is, iteratively adapting the model function p dp,M = f ( L 1 , L 2 ) to the measured n DPOAE until an individual function is obtained p dp,I = f ( L 1 , L 2 ) with individual parameters of a DPOAE level map of the individual by the computer unit, and output of the individual function p dp,I = f ( L 1 , L 2 ) and / or their individual parameters to an output unit of the computer unit.

[0098] During iterative adaptation ( curve fitting,In curve fitting, the model function is adapted to experimentally determined measured values. For this purpose, parameters of this function are changed using a suitable algorithm until the deviation between the measured values ​​and the gradually modified function is minimal according to an optimality criterion (e.g., minimization of the squared error). Algorithms for such iterative fitting are known to those skilled in the art (e.g., Isqcurvefit or Isqnonlin).

[0099] The first pair of levels L 1 1 L 2 1 can set a level L 1 of 67 ± 10 dB and a level L2 of 57 ± 10 dB. These L 1 and L 2 levels have proven to be particularly favorable starting levels. For people with normal hearing, these excitation levels are still within the range up to which the level map increases approximately linearly, and even with hearing losses of up to approximately 40 dB, a DPOAE can still be measured at these levels. Thus, in most cases, values ​​are obtained that are valid for recording the level map.

[0100] The model function defines a linearly increasing 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"). Preferably, at least half of the measured level pairs L 1 i L 2 i by at least 5 dB on both sides away from the ridge assigned L 1 G L 2 G level pairs (where "i" is the index of the measurement from 1 to n).

[0101] Preferably, the different level pairs L 1 i L 2 i presented in a sequence that is identical for each individual. Although this highly simplified and standardized (rigid) procedure makes the approximation of the individual function of a level map somewhat less accurate, it is very fast to execute.

[0102] It can also be advantageous if the predefined, different level pairs { L 1 , L 2} are presented in a sequence that contains a number of k subsequences whose level pairs { L 1 , L 2} essentially transverse to the linearly linked level pairs assigned to the ridge L 1 G , L 2 G By activating subsequences, the ridge can be sampled at multiple locations, increasing the accuracy of determining the individual function of the DPOAE level map.

[0103] Preferably n ≥ 5 and ≤ 12, preferably 6 ≤ n≤ 8. The small number of measurements planned allows for a short measurement time while at the same time providing good recording of the individual function of the DPOAE level map.

[0104] The number of subsequences is advantageous k ≥ 2 and ≤ 5, which ensures good sampling of the ridge of the DPOAE level map.

[0105] It is also advantageous if the first predefined level pair L 1 1 L 2 1 following level pairs L 1 2 … n k , L 2 2 … n k a subsequence with nk 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 previous level pair L 1 i − 1 , L 2 i − 1 be determined, whereby µ = ± 1, in particular +1, and Δ L 1 , Δ L 2 is 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 L 2 = - 1.52 to - 2.78 dB. The factor µdetermines the search direction (towards smaller or larger L 1 -measuring levels) across the ridge.

[0106] Preferably, if the first level pair L 1 1 , L 2 1 and the second pair of levels L 1 2 , L 2 2 two DPOAE with p dp,I (1...2)<, which have a signal-to-noise ratio of >=4 dB each, 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 different 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 level pair L 1 3 , L 2 3 at least by Δ L 1 ≤ - 4 dB different 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 and one point in between near the ridge is measured.

[0107] Preferably, if the first level pair L 1 1 , L 2 1 no DPOAE with p dp,I (1)< 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 L 1 i is reached, or a group of three valid DPOAEs with p dp,I ( i..i+ 2)<, ​​each with a signal-to-noise ratio of >=4 dB, preferably >=10 dB. Compared to a rigid method, this ensures that the ridge is detected even when it is significantly off the expected position for a person with normal hearing, as can be the case with conductive hearing loss.

[0108] Preferably, if in the first subsequence after measurement ati excitation level pairs no group of three valid DPOAEs is produced, each with a signal-to-noise ratio of >=4 dB, preferably >=10 dB, a further subsequence with a higher level pair L 1 i + 1 , L 2 i + 1 started, with the start level pair for the new 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 preferably limited to the technically maximum achievable or sensible level. This maximum level can be, for example, 75-85 dB SPL. This approach allows even individual level maps that deviate significantly from the average to be determined, as well as their function.

[0109] Preferably, after the DPOAE has been recorded from at least 3 level pairs 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 along the line formed by the 3 level pairs and then a fourth level pair L 1 4 , L 2 4 which is located a given distance down the ridge, with the group mean of the ridge direction, φ is used, and based on the four level pairs presented L 1 1 .. 4 , L 2 1 .. 4 determined DPOAE a gradient m of the linear ridge of the level map is determined.

[0110] Preferably, if in the first or second subsequence a group of three valid DPOAEs with p dp,I ( i -2... i )<, each having a signal-to-noise ratio of >=4 dB, preferably >=10 dB, by automatically adapting a suitable calculation function to the corresponding DPOAE p dp,I ( i ... i- 2)< the level 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 forms a maximum, and from there a fourth pair of levels 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 dBis set, and the level pair is preferably based on the projection of the expected ridge onto the L1,L2 plane, ie with Δ L 1 / Δ L 2 ≈ 0.51 ± 0.15 and using the values ​​from the four presented level pairs L 1 i − 2 … i + 1 , L 2 i − 2 … i + 1 determined DPOAE the slope m of the approximately linear ridge of the level map is determined.

[0111] Based on the determined gradient m of the linear ridge of the level map, at least two, preferably three additional level pairs can be L 1 i + 1 … i + 3 , L 2 i + 1 … i + 3 are automatically defined, the excitation levels of which are formed in a subsequence, and which are determined based on the already known position and gradient of the ridge in such a way that it can be expected that valid DPOAEs will be obtained within a measurement time of tm ≤ 40 sto measure, for which a model function is adapted to the preferably four already validly measured DPOAE, and then in the model function the last two or three level pairs are determined so that the expected DPOAE levels are preferably at p DP I i + 1 … i + 3 , p DP I i + 1 … i + 3 ≥ 10 μPa lay.

[0112] Preferably, the level pairs L 1 1 − n , L 2 1 − n presented in a pulsed fashion, with each individual pulse having a duration TD of 2 to 40 ms. By using such a pulsed presentation, the influence of the two source contributions of a DPOAE can be suppressed or separated.

[0113] Preferably, the level pairs L 1 1 .. n , L 2 1 .. n in blocks of several level pairs presented sequentially in pulses L 1 1 .. n , L 2 1 .. n presented, with directly consecutive pairs of levels L 1 1 .. n , L 2 1 .. n different excitation frequencies { f 2 , f1}. In a block, a first pulsed level pair is followed by { f 2.1 , f 1,1} a second level pair with different frequencies { f 2.2 , f 1,2} and if necessary further with { f 2 ,m , f 1 ,m}, where the frequency ratio is always close to f 2, m / f 1, m = 1.2. Several blocks of time-frequency interleaved pulse pairs can be averaged before evaluation. This measure makes it possible to use the time during which the pulse response to a presentation at one frequency pair decays to measure at a different frequency, thus reducing the measurement time compared to a purely sequential approach with regard to the desired measurement frequencies.

[0114] Advantageously, in one process step, the determined individual function of a DPOAE level map and its parameters are stored by the computer unit in a non-volatile memory. The determined raw data can also be stored by the computer unit in the non-volatile memory. The stored data can be used by the computer unit to continuously expand the data set underlying the model function of a level map.

[0115] In Figure 5a system for automatically determining an individual function of a DPOAE level map of a human or animal hearing system is shown in one possible embodiment. The system 1 includes 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 which can be inserted into the auditory canal of an ear. A sound recording means 23, such as a microphone, is arranged in the probe unit 20 and is designed to record sounds coming from the auditory canal. Furthermore, a first and a second sound output means 21 and 22 are provided in the probe unit 20, which function as f1 sound generators (sound output means 21) and as f2 sound generators (sound output means 22). The sound output means 21, 22 can be designed as loudspeakers, for example. It is also possible for only one sound output means oronly one loudspeaker should be provided, which can play two sounds simultaneously. f 1 , f 2 is set up and in particular has a highly linear characteristic. The probe unit 20 is connected, for example, via a cable connection 2 to the control unit, which contains the computer unit 10. The cable connection 2 preferably contains shielded lines 3, 4, 5 via which the sound output means 21, 22 and the sound 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. As an alternative to 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 that preferably has a short range.

[0116] 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 , L 2 ) for a model level map of a human or animal hearing system and the parameters belonging to this model function are stored. The instruction for carrying out a method described here is also stored in the non-volatile memory 16. The system 1 further has an output means 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 hearing system and its parameters can be output by the system 1 and made accessible to a user. The output means 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.

[0117] To carry out an automatic measurement process to create an individual function of a DPOAE level map of a human or animal ear, the probe unit 23 is inserted in the direction of the arrow 40 into the auditory canal 31 of an ear 30 (in Fig. 5 The procedure is described below with reference to the Figures 7 and 8 explained.

[0118] But first of all, Figure 6 As an example, a model function is shown, the three-dimensional graph 70 of which corresponds to a model level map. The model function shown as an example is based on the measurement data from p ≥ 2, present p = 6, normal hearing individuals with N ≥ 40, present N = 47, measured different level pairs L 1 1 … N L 2 1 … N at excitation frequencies f 2 = 2 kHz and f 1 = 1.67 kHz. The excitation frequencies f 2 and f 1 of a level pair { L 1 , L2} are preferably linked via a frequency ratio f 2 / f 1 = 1.2. A specific distortion product was evaluated, which is preferably at the frequency f dp = 2 f 1 -f 2. The superscript indices in brackets represent the 1st to Nth measuring points.

[0119] The model function defines an approximately linearly increasing ridge 73, to which approximately linearly linked L 1 G L 2 G Lines across the ridge can be defined by the relationship L 2 + aL 1 = C, where C is any constant, and where a the gradient parameter of the projection of the ridge onto the { L 1 , L2}-plane. In the mathematical sense, 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 towards this ridge and swinging in. In the { L 1 , L 2}-level 71 is the transformed L 1 ′ L 2 ′ -coordinate system 72 is drawn, which is created 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. L 2 ′ -axis corresponds to the projection of the ridge of the level map onto the { L 1 , L 2}-plane. The L 1 ′ The axis intersects the model hill orthogonally, as approximated by the water level map. This section through the hill perpendicular to the ridge is approximated by a second-order parabola whose spread is given by a parameter c, and which is entered into 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 is the level of any DPOAE or of one on the ridge and m is the gradient of the ridge along the L 2 ′ -Axis.

[0120] The L 1 ′ , L 2 ′ - Coordinate system is located in the direction from 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

[0121] The projection of the ridge of the L dp -hill on the { L 1 , L 2}-level of the L 2 ′ -axis. Furthermore, the point {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 -hill on the { L 1 , L 2}-plane, given by the already mentioned L 2 ′ -axis. The angle φ is therefore the angle by which the L 2 ′ -axis opposite the L 2 axis. The base point of the ridge can be interpreted in a broader sense as equivalent, but not identical, to the "estimated distortion product level" (edpt), as known from [P. Boege and T. Janssen., J. Acoust. Soc. Am., 111(4): 1810-1818, 2002].

[0122] The model function for the level map can be used for the validity range of positive L dp be described by five free parameters: a ; b; c; L 2 , edpt ′ ; m In order to calculate this area from measured values, at least 5 DPOAE are required.

[0123] The method is based on the adaptation of 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 for automatically determining an individual function of a DPOAE level map with p dp = f ( L 1 , L 2 ) of a human or animal hearing are assigned to the hearing of an individual from the Figure 5 apparent system n predefined, e.g. n = 6 predefined, excitation level pairs { L 1 , L 2} 51, 52, 53, 54, 55, 56. These six predefined excitation level pairs { L 1 , L 2} 51, 52, 53, 54, 55, 56 are exemplary in Figure 6 in the { L 1 , L 2} level. From these 6 predefined excitation level pairs { L 1 , L2} 51, 52, 53, 54, 55, 56, which are presented in two subsequences 57, 58, DPOAE are then determined, which are used via the method for determining the individual function of a DPOAE level map.

[0124] According to Figure 7 In a first step 110 of the method, the previously described model function is first read from the non-volatile memory 16 into the computer unit 10 of the system 1, or the main memory 15 of the computer unit 10. After reading in the model function, the system 1, in the second step 120, generates a number of different level pairs L 1 1 ... n , L 2 1 ... n an excitation frequency pair { f 1 , f 2} is output via the sound output means 21, 22 of the probe unit 20 or presented to an individual and the corresponding DPOAE of the individual is 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 << NThe corresponding DPOAEs are forwarded to the computer unit 10 for further processing via the AD / DA converter unit 12. The superscript indices in parentheses represent the 1st to nth measurement points.

[0125] The second step 120 includes, in a first variant of the method, which can be referred to as an adaptive variant, a series of sub-steps 121 to 127, which are described below with reference to Figure 8 be explained in more detail.

[0126] According to Figure 8 In a first sub-step 121 of the second step 120, a start level L 1 1 L 2 1 (preferably a level L 1 of 67 ± 10 dB and a level L 2 of 57 ± 10 dB) for a first level pair from the non-volatile memory 16 into the computer unit 10. Furthermore, in this sub-step 121, the step sizes Δ L 1 , Δ L 2 for the other level pairs L 1 2 … n L 2 2 .. n and thresholds for search direction decisions L dp , min G 1 ; SNR min ) is read into the computer unit 10. SNR min denotes the desired SNR (signal-to-noise ratio) and L dp , min G 1 denotes the DPOAE level on the ridge, which must be present at least along a first subsequence of k subsequences so that a subsequent subsequence below the first can still be expected with sufficient SNR. If this value is not reached, the next subsequence above the first, i.e., up the ridge, is sampled to avoid excessively long measurement times to achieve a sufficient SNR. The step sizes Δ L 1 , Δ L 2 denote 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 where Δ L 2 = 0 to -2.78 dB, preferably Δ L 2 = - 1.52 to -2.78 dB.

[0127] In a second sub-step 122 of the second step, the measurements of the first subsequence of k subsequences are performed perpendicular to the assumed degree of the individual function of a level map. The DPOAEs are performed at the excitation frequencies f 2 = 2 kHz and f 1 = 1.67 kHz described above. The excitation frequencies f 2 and f 1 of a level pair { L 1 , L 2} are preferably linked by a frequency ratio of approximately f 2 / f 1 = 1.2. The subsequence belongs to a number of k subsequences, where k ≥2 and ≤5. In each subsequence, a number of n k Level pairs {L 1 , L 2} measured.

[0128] The starting level L 1 1 L 2 1 is adjusted according to the specified step sizes Δ L 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 falling or no rising edge is measured in the measured subsequence, the search direction is reversed and Δ L 1 ' = - Δ L 1 '

[0129] In a third sub-step 123, it is checked whether at least three valid DPOAEs were measured. If this check is positive, i.e. three valid DPOAEs were measured, the procedure continues to the next sub-step 124. If no three valid DPOAEs were measured, the measurement is repeated, in which a new excitation level L 1 (1)< , L 2 (1)< is calculated from the original excitation level L 1 (old)< , L 2 (old)< according to L 2 l = L 2 alt + ΔL 2 ′ cos φ , L l l = L l alt + ΔL 2 ′ sin φ is determined.

[0130] In the following fourth sub-step 124, the position of the ridge of the individual function is determined using the three valid measured values, e.g. by solving a parabola equation and finding the individual maximum according to the function: L dp ′ G 1 = f L 1 1 .. 3 L 2 1 .. 3

[0131] Here means L dp ′ G 1 the point on the estimated ridge of the individual model function whose corresponding excitation level pair on the L 1 1 .. 3 L 2 1 .. 3 formed line. The position of the ridge of the individual function at the higher excitation levels L (1..3)< is now already known from sub-step 124, but the slope of the ridge, ie the parameter m, is not.

[0132] In the subsequent fifth sub-step 125 of the second step 120, a measurement of a second sub-sequence is carried out along the suspected ridge, whereby only one measured value is determined. The measurement is carried out according to the formula L 1 4 = L dp ′ G 1 − Δ L 2 ′ sin φ .

[0133] falls below L dp ′ G 1 a preset limit L dp , min ′ G 1 , this step is carried out towards higher levels (Δ L 2 = - Δ L 2 ).

[0134] The DPOAE value measured there L dp 4 is subsequently used in the sixth sub-step 126 to determine the individual gradient of the ridge, m.

[0135] In the sixth sub-step 126 of the second step 120, the individual gradient of the ridge is calculated according to the formula m = f(L dp (G , 1) < , L 1 (G ,< 1)< , L 2 (G ,< 1)< , L dp (4)< , L 1 (4)< , L (4)< ) . Based on the determined gradient m of the ridge, a starting level is now determined L 1 (5)< , L 2 (5)< for the third subsequence.

[0136] In the seventh sub-step 127 of the second step 120, the measurements of the third sub-sequence are now carried out transversely to the assumed ridge of the function: A variation of Δ L 1 ′ in L 1 n + 1 = L 1 n + Δ L 1 ′ cos φ .

[0137] Preferably, at least half of the level pairs { L 1 ,L 2} ,where measurements are taken to be at least 5 dB on both sides away from the group of frequencies assigned to the ridge (the model function). L 1 G L 2 G Level pairs.

[0138] With the measured values ​​determined in accordance with the second step 120 and its sub-steps 121 to 127, the model function already presented is now adapted to the measured values ​​obtained in a third step 130 in the computer unit 10. In this case, the three-dimensional model function is applied to the measured DPOAE values p dp,M = f ( L 1 ,L 2 ) is adjusted. The adjustment is carried out using the mathematical methods of the adjustment calculation, e.g. with the method of least squares, ie with the iterative minimization of 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 (according to the associated L 1 , L2 coordinates) until an individual function is obtained p dp , 1 = f ( L 1 ,L 2 ) with individual parameters of a DPOAE function and level map of the individual by the computer unit 10. This provides a simple way to obtain an individual function / level map of the hearing of an individual with greatly reduced measurement effort in a short time.

[0139] In a fourth step 140, the individually adapted function and its function parameters are output in an output means 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 means 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.

[0140] In a possible further method step, the determined individual function of a DPOAE level map 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, to continuously expand the data set underlying the model function of a level map.

[0141] The following insights can be gained from the obtained individually adapted function and the associated functional parameters: An approximate distortion product threshold can be calculated, which provides information about the threshold of the input signal for the inner hair cells of the hearing being measured. 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 hearing. 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 a pure conductive loss, the angle (expressed in the function by the parameter a) does not change, instead the hill shifts in the first approximation to the same extent towards higher L 1 - and L2 -level. If, for example, the shift of the hill (compared to the norm values, or compared 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 can be concluded that there is a pure conductive loss. The steepness of the ridge, expressed by the parameter m, allows conclusions to be drawn about a possible conductive loss. As long as the hearing loss is below 30 dB, it can be expected that in the case of a pure conductive loss the slope corresponds to the norm values, whereas in the case of a deviation from the norm value a proportional reduction of the retrograde middle ear transmission at f dp is indexed.

[0142] In an alternative variant of the method, instead of the sub-steps 121 to 127, a number of nfixed or predefined but different level pairs { L 1 ,L 2} (where n preferably ≥5 and ≤ 12, in particular ≥ 5 and ≤ 8) are output by the system and the response of an individual's hearing to these level pairs { L 1 ,L 2}. 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. 6 ) are measured, where 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 procedure. The number n the level pairs { L 1 , L2} is designed according to a balance between measuring time (as few measuring points as possible) and achievable accuracy (as many points as possible).

[0143] In this rigid procedure with fixed excitation levels, for example, 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 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 (cf. Fig. 6 ). The election follows L 1 ′ = 0 ± 6 dB The aim is to reliably measure the position of the ridge with three points that are perpendicular to the assumed position of the ridge: at f 2 = 2 kHz the DPOAE falls with Δ L 1 ′ ± 6 dB typically drops to about 50% of the maximum value. If the measurement is primarily carried out on individuals with normal hearing, as is usually the case with screening tests, the rigid arrangement will yield good results. However, outliers must be detected. This is possible using the squared error of the model fit. If the error is too high, e.g., if the rms error (rms: root-mean-square) is larger than 5 µPa, Further level pairs must be measured until the error is small enough. Δ L 1 ′ -steps. The same procedure must be followed if individual measurement points cannot be recorded due to insufficient signal-to-noise ratio.

[0144] Finally, it should be noted that, in contrast to the frequency ratio used and described above, f 2 / f 1 of 1.2, a different frequency ratio can also be selected. This way, the frequency ratio f 2 / f1 can also be set to another suitable value between 1.15 and 1.35. Furthermore, the frequency ratio f 2 / f 1 be a function of f2. Reference list

[0145] 1System 2Cable connection 3First line 4Second line 5Third line 6Fourth line 10Computer unit 11Output device 12AD / DA converter unit 13DA converter 14AD converter 15RAM 16Non-volatile memory with stored model function 20Probe unit, OAE probe 21First sound output device, f1 sound generator 22Second sound output device, f2 sound generator 23Sound recording device, microphone 24Probe tip 30Ear 31Ear canal 40Arrow 51Excitation 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 , L 2} 55Excitation level pair {L 1 , L 2} 56Excitation level pair { L 1 , L 2} 57first subsequence 58second / further subsequence 70Graph / Model Level Map 71{ L 1 , L 2}-level 72 transformed L 1 ′ L 2 ′ -Coordinate system 73Grat (of the DPOAE model gauge 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

[0146] The method described here for automatically determining an individual function of a DPOAE level map can avoid errors in the extrapolation of growth functions, which can inherently occur in the methods for measuring the distortion product threshold according to the previously described state of the art. Furthermore, additional data can be obtained that are then available for diagnosis. In addition to the distortion product threshold, L edpt and the slope of the growth function, the method described in PCT / EP2017 / 000334 also allows data on the frequency resolution and compression of the underlying traveling waves and the acoustic conduction loss to be acquired. Advantageously, four pieces of information can be obtained instead of the two in the prior art with the same or even less time required for the measurement points, and estimation errors in the parameters obtained so far (the distortion product threshold L edptand the slope of the growth function).

[0147] In the automatic determination of an individual function of a DPOAE level map described here, the primary tones of each level pair are preferably selected so that both traveling waves at the f 2 imaging location have approximately equal amplitudes. f 1 -Traveling wave at f 2 imaging location has not yet reached its maximum, it is preferably stimulated much more strongly, at least at moderate excitation levels at which the cochlear amplifier is active. However, if the excitation level combination lies significantly outside the individually optimal path, the different strengths of the traveling waves in the area of ​​the f 2 -tone can weaken or even amplify the phenomenon shown. Therefore, a combination with the method described in PCT / EP2017 / 000334 can be useful to determine an individual function p dp,I = f ( L1 ,L 2 ) with individual parameters of a DPOAE level map.

[0148] For a detailed description of the "water level map method", please refer to PCT / EP2017 / 000334.

Claims

1. A method for detecting distortion products of otoacoustic emissions (DPOAE) in an auditory organ, comprising the steps of: (a) output of a first primary tone pair {f1,1, L1,1, f2,1, L2,1} each consisting of a first primary tone having a frequency {f1,1 and a sound pressure level L1,1 and a second primary tone having a frequency f2,1 and a sound pressure level L2,1, with f2,1> f1,1, and (b) detection of evoked distortion products of otoacoustic emissions (DPOAE), wherein the first primary tone {f1,1, L1,1} is output with a time delay tlag after the second primary tone {f2,1, L2,1}, wherein at least one further primary tone pair is output each consisting of a first primary tone having a frequency f1,n and a sound pressure level L1,n and a second primary tone having a frequency f2,n and a sound pressure level L2,n, with f2,n > f1,n, wherein the second primary tone {f2,n, L2,n} of the at least one further nth primary tone pair is output with a time delay tlag after the first primary tone {f1,n, L1,n} of this primary tone pair, wherein {f1,1, L1,1} = {f1,n, L1,n} and {f2,1, L2,1} = {f2,n, L2,n}, and wherein the method further comprises a step of comparing the DPOAEs evoked by the output of the first primary tone pair {f1,1, L1,1, f2,1, L2,1 } with the DPOAEs evoked by the output of each nth further primary tone pair {f1,n, L1,n, f2,n, L2,n}.

2. The method according to claim 1, characterised in that the output of the at least one further nth primary tone pair {f1,n, L1,n, f2,n, L2,n} occurs before or after the output of the first primary tone pair {f1,1, L1,1, f2,1, L2,1}.

3. The method according to any one of claims 1 or 2, wherein n = 2.

4. The method according to any one of the preceding claims, characterised in that the first primary tone {f1,1, L1,1} and / or {f1,n, L1,n} ("f1 pulse") and optionally the second primary tone {f2,1, L2,1} and / or {f2,n, L2,n} ("f2 pulse") are presented as a pulsed tone.

5. The method according to claim 4, characterised in that the pulse length of the f1 pulse of the first primary tone pair [f1,1, L1,1} is shorter than the pulse length of the f2 pulse of the first primary tone pair {f2,1, L2,1}, and / or the pulse length of the f2 pulse of the nth further primary tone pair {f2,n, L2,n} is shorter than the pulse length of the f1 pulse of the nth further primary tone pair {f1,n, L1,n}.

6. The method according to claim 4 or 5, characterised in that the f1 pulse of the first primary tone pair {f1,1, L1,1; f2,1, L2,1} is switched off before or after the end of the f2 pulse of the first primary tone pair.

7. The method according to any one of the preceding claims, characterised in that the time delay tlag is between 10 ms and 0.1 ms, preferably between 5 ms and 0.5 ms.

8. The method according to any one of the preceding claims, characterised in that the duration of the f1 pulse of the first and optionally of each further nth primary tone pair and / or the duration of the f2 pulse of the first and optionally of each further nth primary tone pair is chosen to be longer than the latency of the evoked DPOAE, preferably at least twice, more preferably at least three times and most preferably at least five times as long.

9. The method according to any one of the preceding claims, characterised in that the duration of the f1 pulse {f1,1, L1,1} of the first primary tone pair and / or of the f2 pulse {f2,n, L2,n} of the nth further primary tone pair is 200 ms or less, 100 ms or less, 50 ms or less, between 40 ms and 1 ms, between 30 ms and 2 ms or between 25 ms and 5 ms.

10. The method according to any one of the preceding claims, characterised in that a set of the first primary tone pair {f1,1, L1,1; f2,1, L2,1} and the at least one further primary tone pair {f1,n, L1,n; f2,n, L2,n} are output in a block which is repeated several times during the measurement period.

11. The method according to any one of the preceding claims, characterised in that the duration of the first and second primary tone of each pair of primary tones is between 2 ms and 20 ms.

12. The method according to any one of claims 10 to 11, characterised in that in a block the beginning of a primary tone pair follows the beginning of the primary tone pair immediately preceding in the block with a time interval Ta, where Ta is preferably > 10 ms.

13. The method according to any one of claims 10 to 12, characterised in that in a block the second excitation frequencies f2 of two immediately successive primary tone pairs are at least one octave apart.

14. The method according to any one of claims 10 to 13, characterised in that during the measurement period, for primary tone pairs of equal second excitation frequencies f2, the measured sound pressure levels of the DPOAE are averaged.

15. The method according to any one of claims 10 to 14, characterised in that the or each block of primary tone pairs is presented during a block time which is selected such that there is a time interval of 30 ms to 100 ms, preferably of at least 70 ms, between the beginning of a first and a subsequent primary tone pair having the same excitation frequency f2.

16. The method according to any one of claims 1 to 15, characterised in that at the beginning of the measurements it is checked whether the frequency fdp of one of the DPOAEs interferes with a spontaneous emission (SOAE).

17. The method according to any one of claims 10 to 16, characterised in that at least two sets with at least partially different primary tone pairs with respect to the second excitation frequency f2 are selected, wherein the blocks of the individual sets are presented one after the other in time, preferably characterised in that that the sound pressure levels of the DPOAEs are measured and averaged for all second excitation frequencies f2 contained in the or each set at a second sound pressure level L2 respectively assigned to the excitation frequency f2, and the measurements are carried out at least once for new sound pressure levels L2.

18. The method according to any one of the preceding claims, further comprising automatically determining an individual function of a DPOAE level map with pdp,I = f(L1, L2), wherein DPOAE is represented as sound pressure p as a function of the levels L1 and L2 of the two primary tones used to generate the DPOAE, to determine the optimal DPOAE excitation level: - reading (110) a model function pdp,M = f(L1, L2) with model parameters of a DPOAE level map (70), based on a number of N DPOAE measurements of an excitation frequency pair f1,f2 with respectively different level pairs L 1 1 … N L 2 1 … N in a population (p) of normal-hearing persons, into a working memory of a computer unit, where N ≥ 40 and p ≥ 2, - automatic presentation (120) of n different level pairs L 1 1 ... n L 2 1 ... n (51, 52, 53, 54, 55, 56) of an excitation frequency pair f1, f2 via sound output means (21, 22) to an individual and detection of the corresponding DPOAE of the individual via sound recording means (23), wherein at least the first level pair L 1 1 L 2 1 (51) is predefined and wherein n ≪ N, - iterative adaptation of the model function pdp,M = f(L1, L2) to the measured n DPOAEs until an individual function pdp,I = f(L1, L2) with individual parameters of a DPOAE level map of the individual is obtained by the computer unit, and - output of the individual function pdp,I = f(L1, L2) and / or its individual parameters to an output means of the computer unit.