CN118018940A - Loudness perception model and round window excitation loudness calculation method applied by same - Google Patents
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Abstract
The invention discloses a loudness perception model and an applied round window excitation loudness calculation method, wherein an auditory peripheral model is established, and the auditory peripheral model comprises an outer ear filter model, a middle ear dynamics model and a cochlear dynamics model, and can calculate the basal membrane speed under acoustic excitation and round window excitation; the data processing backend stage converts the base film speed to loudness. Based on the loudness perception model, the round window excitation loudness calculation method provided by the invention comprises the following steps: 1) The exciting force of the actuator is input to a round window membrane of the middle ear dynamics model to obtain cochlear fluid acceleration; 2) Substituting the cochlear fluid acceleration into a cochlear dynamics model to obtain the basal membrane speed under round window excitation; 3) And substituting the substrate film speed into the data processing rear end to obtain the excitation loudness of the round window. The invention can provide a loudness prediction value for the development of a round window excitation type artificial middle ear hearing test and match algorithm.
Description
Technical Field
The invention relates to the technical field of hearing assistance, in particular to a loudness perception model and an applied round window excitation loudness calculation method.
Background
The actuator of a conventional artificial middle ear implant acts on the ossicles, requiring the patient's ossicular chain to be intact, as shown in fig. 3. However, many patients are also associated with ossicular deformity, ossicular corrosion, etc., and cannot provide a perfect ossicle, which in turn makes the traditional artificial middle ear implantable. Aiming at the problem, colletti is equal to avoiding a damaged ossicular chain in clinical implantation in 2006, an actuator of VIBRANT SOUNDBRIDGE brand artificial middle ear produced by Austria MED-EL company is directly implanted at the round window which is the other entrance of a cochlea of a patient, and the round window membrane 7 is mechanically excited by the actuator to compensate hearing, so that a good clinical effect is achieved, and the principle is shown in figure 4. The round window excitation hearing loss compensation mode expands the treatment field of the traditional artificial middle ear, so that the round window excitation hearing loss compensation mode can treat mixed deafness accompanied with abnormal tympanic cavity or ossicular chain (such as congenital outer middle ear deformity, ossicular corrosion caused by otitis media and the like). The round window excitation artificial middle ear has been widely used in clinic due to the advantages, but the problems of large initial test and matching error, difficult later fine tuning and the like occur in the test and matching process. This is mainly because there has been no hearing test-fit algorithm for this excitation pattern so far, and the test-fit has been accomplished clinically by borrowing a hearing aid test-fit algorithm (such as NAL proposed by the national acoustic laboratory in australia, DSL proposed by the national audiology center in canada, etc.), or the like. These classical hearing aid fitting algorithms are developed specifically for the sound transmission characteristics of hearing aids. However, round window excitation hearing compensation, input energy enters the cochlea through the cochlea round window; hearing aids compensate for hearing, and input energy enters the cochlea through the eardrum, ossicular chain, and cochlea oval window. The two energy transmission paths into the cochlea are different, and the loudness perception mechanism is different, so that the hearing aid fitting algorithm is used for the round window excitation effect poorly. Therefore, the hearing test algorithm of the round window excitation needs to be specially developed.
Loudness is an important parameter of sound quality that reflects the subjective perception of sound intensity by the human auditory center. In order to accurately calculate the sound sensing effect of the human ear, electroacoustic equipment such as a hearing aid is designed, various loudness sensing calculation methods are established by researchers at home and abroad, and the classical is the Moore-Glasberg method (ISO 532-2:2017) which is listed as a standard by the International organization for standardization. The typical hearing aid fitting algorithm is built based on a loudness perception calculation method, and the NAL algorithm proposed by the acoustic laboratory in Australia is designed based on a Moore-Glasberg loudness perception calculation method. As shown in fig. 5, in the Moore-Glasberg loudness perception calculation method, after the sound signal passes through the outer ear and middle ear filters, the frequency of the sound signal is decomposed by using a filter bank, so as to calculate the excitation on each equivalent rectangular bandwidth, and finally, the loudness under acoustic excitation is calculated.
However, this loudness perception calculation method cannot be used for round window excitation because it suffers from the following drawbacks:
Less than 1: the loudness perception calculation method adopts a filter to directly simulate the sound transmission characteristics of the outer ear and the middle ear, does not consider physiological structures such as eardrum, malleus, incus, stapes, tendons and the like in the middle ear, is similar to a black box model, and cannot simulate conductive hearing injury such as ossicular chain injury and the like and mixed hearing injury accompanied by the conductive hearing injury. The two types of hearing impairment are patients mainly aiming at round window excitation, so that the traditional loudness calculation model can not simulate the main hearing impairment state of the round window excitation patients.
Less than 2: the loudness perception calculation method is fit to the auditory test result of normal human ears under acoustic excitation. The round window excitation type artificial middle ear is an implanted hearing aid device and cannot be used for a normal human ear to perform audiometry experiments. Therefore, a loudness model cannot be established by adopting a method of fitting a filter to the perception of the loudness of the human ear under excitation of the round window.
Less than 3: the loudness perception calculation method is fit with human ear loudness perception under free field sound excitation, sound is transmitted into the middle ear from an auditory canal and then transmitted into the cochlea from the stapes of the middle ear through the oval window of the cochlea, and the method can be applied to hearing aids and other hearing aids with the same path as the normal human ear sound transmission. However, the round window excited artificial middle ear, whose input energy crosses the middle ear, passes directly into the cochlea through another window (round window) of the excited cochlea. The sound transmission path of the round window excitation is different from the transmission path of the normal sound. Therefore, the loudness model cannot be applied to round window excitation type artificial middle ear.
Disclosure of Invention
Aiming at the technical defects, the invention aims to provide a loudness perception model and an applied round window excitation loudness calculation method, wherein the model can simulate and analyze the loudness perception characteristics of conductive hearing impairment and hybrid hearing impairment patients by changing the material properties of tissues in the middle ear of the model, can calculate the speed of a basement membrane under acoustic excitation and round window excitation, and convert the basement membrane speed into loudness, and the algorithm can solve the problem that the round window excitation loudness cannot be accurately calculated at present.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention provides a loudness perception model and an applied round window excitation loudness calculation method, wherein the method comprises a model processing stage and a model processing rear-end stage, and the model processing stage comprises the following steps:
step 1: establishing a loudness perception model comprising an outer ear filter model, a middle ear dynamics model and a cochlea dynamics model;
Step 2: inputting exciting force of a round window exciting artificial middle ear actuator to a round window membrane in a middle ear dynamics model in the constructed loudness perception model, and calculating to obtain cochlear fluid acceleration under round window excitation;
step 3: substituting the cochlear fluid acceleration into a cochlear dynamics model in the constructed loudness perception model, and calculating to obtain the basal membrane speed on each cochlear segment under the excitation of the round window.
The model processing back-end stage comprises the following steps:
Step 4: absolute values of basal membrane velocities on each cochlear segment; integrating the cochlea in time to obtain initial excitation on each cochlea segment;
Step 5: dividing a cochlea into a plurality of excitation sections, wherein each excitation section comprises a plurality of cochlea segments, and averaging the initial excitation of the cochlea segments in each excitation section to obtain the excitation of each excitation section;
Step 6: converting the excitation of each excitation segment into a specific loudness of each excitation segment; summing the specific loudness of all the excitation segments to obtain initial loudness;
Step 7: converting the initial loudness L I to a loudness level L L according to the function S; the function S is L L＝52.45tanh(1.427(LI -0.68)) +37.2;
Step 8: according to the function P, converting the loudness level L L into loudness L; the function P is l=8×10 -4(0.1LL+1.2)4.4.
Preferably, in step 1, the method for establishing the middle ear dynamics model is as follows: the malleus, the incus, the stapes and the cochlea fluid are simplified into mass, the vestibular aqueduct and the cochlea aqueduct are simplified into damping, and the tympanic membrane, the anterior malleus ligament, the posterior incus ligament, the stapedial annular ligament, the anvil-hammer joint, the anvil-stirrup joint and the round window membrane are simplified into rigidity and damping; the model can simulate the sound transmission characteristics of human ears under acoustic excitation and round window excitation while having quick calculation.
Preferably, in step 1, the method for establishing the cochlear dynamics model is as follows: simplifying the cochlea into a one-dimensional fluidly coupled conical cochlea with a round window and an oval window; the cochlea is divided into 100 segments by the model, and each segment consists of basal membrane mass, reticular plate mass, covering membrane mass, basal membrane longitudinal coupling rigidity and damping, basal membrane bending rigidity and damping, external hair cell rigidity and damping, cilia bundle rigidity and damping and covering membrane rigidity and damping; the model can accurately calculate basal membrane velocities on each cochlear segment under acoustic excitation and round window excitation.
Preferably, in step 1, a digital filter is used to build an external ear filter model, specifically: where P E is the sound pressure at the eardrum, P Free is the sound pressure at the free field source, n is the nth sample point of the time signal, k is the order of the filter, and a (k) is the gain parameter of the kth order filter.
Preferably, in step 1, the differential equation of motion of the middle ear dynamics model is:
Wherein m M、mI、mS and m CF are respectively a malleus mass, an incus mass, a stapes mass and a cochlear fluid mass, k AML、kPIL、kAL、kE、kIMJ、kISJ and k RW are respectively a malleus anterior ligament stiffness, an incus posterior ligament stiffness, a stapedial annular ligament stiffness, an eardrum stiffness, an incus hammer joint stiffness, an incus stirrup joint stiffness and a round window membrane stiffness, c AML、cPIL、cAL、cE、cIMJ、cISJ、cVA、cCA and c RW are respectively a malleus anterior ligament damping, an incus posterior ligament damping, a stapedial annular ligament damping, an eardrum damping, an incus hammer joint damping, an incus stirrup joint damping, a vestibular aqueduct damping, a cochlear aqueduct damping and a round window membrane damping, a E is an eardrum area, and F RW is a force of a round window excitation type artificial middle ear on the round window membrane.
Preferably, in step 1, the cochlear dynamics model reduces the cochlea to a one-dimensional fluidly coupled conical cochlea, and the transfer of the traveling wave in the cochlear dynamics model is described as:
Wherein p is the pressure difference across the cochlear septum, Radial acceleration in cochlear fluid, ρ is the density of cochlear fluid, H is the effective height of vestibular and scala tympani, h=pi 2AC/(8WB);AC is the cross-sectional area of cochlea, and W B is the width of basal membrane;
The driving of the cochlear dynamics model is the pressure difference between the oval window membrane and the round window membrane;
The cochlea dynamic model divides the cochlea into 100 sections, and the stress analysis of each section is very similar to the differential equation of motion of the ith section of the cochlea dynamic model, which is as follows:
Wherein m Bi、mRi and m Ti are respectively the base film mass, the net plate mass and the cover film mass on the i-th section, k Li、kBi、kOHCi、kHBi and k Ti are respectively the base film longitudinal coupling stiffness, the base film bending stiffness, the outer hair cell stiffness, the cilia bundle stiffness and the cover film stiffness, and c Li、cBi、cOHCi、cHBi and c Ti are respectively the base film longitudinal coupling damping, the base film bending damping, the outer hair cell damping, the cilia bundle damping and the cover film damping.
Preferably, in step 4, the basement membrane dormitory on each segment of the cochlea is absolute and time calculated
Ei,0＝0
And (5) integrating to obtain initial excitation:
where E i,t is the initial excitation of the ith substrate film segment at time t, v i,t is the speed of the ith substrate film segment at time t, sampling frequency f s =200 kHz, time constant τ=15 ms.
Preferably, in step 5, according to 1/3 octave, the cochlea segment having a characteristic frequency of 88.4-11313.7Hz is divided into 21 excitation segments, and the cochlea segments having a characteristic frequency of less than 88.4Hz and greater than 11313.7Hz are respectively taken as one excitation segment, and the cochlea is divided into 23 excitation segments in total; excitation E x on the x-th excitation segment was calculated as:
wherein M is the number of cochlear fragments contained in the x-th excitation segment.
Preferably, in step 6, the excitation on the x-th excitation segment is converted to a specific loudness on the x-th excitation segment by:
Wherein C x,αx and a x are constants for calculating specific loudness on the x-th excitation segment, and are different in each excitation segment; the specific loudness over all excitation segments is summed to give the initial loudness L I:
The invention has the beneficial effects that:
1. The loudness perception model is based on the physiological structure of human ears, and can simulate and analyze the loudness perception characteristics of conductive hearing loss and mixed hearing loss patients by changing the properties of tissue materials in the middle ear and the cochlea in the model.
2. The hearing peripheral model parameters in the loudness perception model are based on the existing experimental report, and the optimization of the model processing back-end stage parameters is based on loudness perception data under acoustic excitation. Therefore, the establishment of the loudness perception model does not need a round window excitation human ear audiometry experiment.
3. According to the loudness model based on the human ear physiological structure, the round window film is considered in the model, the speed of the basement membrane under the excitation of the round window can be calculated, and the loudness can be calculated according to the speed of the basement membrane at the rear stage of model processing. Thus, the method is applicable to a variety of applications. The loudness perception model disclosed by the invention can be used for calculating the loudness of round window excitation, and the defect that the existing loudness model can only be used for analyzing the loudness perception characteristics of a normal sound transmission way is overcome.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a simplified schematic illustration of a human ear;
fig. 2 is a schematic view of a cochlea cross-section
FIG. 3 is a schematic diagram of a conventional artificial middle ear;
FIG. 4 is a schematic illustration of a round window excitation type artificial middle ear;
FIG. 5 is a computational flow diagram of the Moore-Glasberg method in International Standard ISO 532-2:2017;
FIG. 6 is a flowchart of a loudness perception model and an applied round window excitation loudness calculation method provided by the embodiment of the present invention;
FIG. 7 is a schematic diagram of a function S provided by an example of the present invention;
FIG. 8 is a schematic diagram of a function P provided by an example of the present invention;
FIG. 9 is a graph comparing the outer ear transfer function provided by an example of the present invention with standard ANSIS 3.4.4;
Fig. 10 is a schematic representation of a middle ear dynamics model provided by an example of the present invention;
FIG. 11 is a graph comparing middle ear transfer functions with experimental data of Nakajima et al under acoustic excitation provided by an example of the present invention;
FIG. 12 is a graph comparing experimental data of stapes velocity with statistics of Koch et al at 94dB sound pressure level excitation provided by the present example;
FIG. 13 is a graph showing the comparison of round window excitation transfer function provided by the example of the present invention with experimental data such as Nakajima;
fig. 14 is a simplified schematic of a one-dimensional fluidly coupled conical cochlea;
FIG. 15 is a schematic view of the ith segment of the cochlear dynamics model provided by the example of the present invention;
FIG. 16 is a graph showing the frequency selective characteristics of the base film according to the example of the present invention compared with experimental data such as Kringlebotn;
FIG. 17 is a graph comparing the frequency response of the base film provided by the example of the present invention with the experimental data of Gundersen et al and Stenfelt et al;
FIG. 18 is a schematic diagram of an external hair cell circuit model provided by an example of the present invention;
FIG. 19 is a graph comparing basal membrane displacement of active and passive models provided by examples of the present invention with experimental data of Johnstone et al surviving and dying cochlea;
FIG. 20 is a graph comparing the equal loudness curves of the loudness perception model of the present invention with the International Standard ISO 226;
FIG. 21 is a graph of the loudness of bandwidth noise versus experimental data such as Zwicker for a loudness perception model of the present invention under acoustic excitation;
Fig. 22 is a plot of loudness of pure tone under frequency domain masking versus Zwicker experimental data.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1-4, the human ear is mainly composed of three parts, namely an outer ear, a middle ear and an inner ear. The normal human ear sense sound is that firstly, the auricle of the outer ear collects sound to the external auditory meatus 1 to cause the eardrum 2 to vibrate; then drives the malleus 3 of the middle ear to move and transfer to the incus 4 and the stapes 5; the stapes bone, through its floor, transmits vibrational energy to the cochlea of the inner ear through the cochlea oval window membrane 30; the cochlea is subjected to fluid-solid coupling action of the lymph fluid 6 in the cochlea and the basal lamina 13 and the active amplification function of the outer hair cells 15 (the micro vibration induced by the basal lamina is actively amplified), so that the vibration energy input by the inner hair cells in the cochlea is induced, nerve pulses are generated and transmitted to the auditory nerve, and then the sound is heard by a person. The sensorineural hearing impairment is mainly caused by damage of the outer hair cells 15, and cannot amplify the input weak vibration signal, so that the patient cannot hear the external low-intensity sound. The hearing aid device enables a patient to hear by amplifying weak sound signals in a targeted manner before the weak sound signals are input into a cochlea, so that hearing impairment of the patient is compensated.
The artificial middle ear mainly comprises a microphone 20, a signal processing unit 21, an actuator 22 implanted in the body and a power supply 23. Wherein actuator 22 is typically coupled to the ossicles of the middle ear, such as the incus body, incus long process, stapes, etc. The working process is as follows: the microphone 20 firstly collects sound, converts the sound into an electric signal and transmits the electric signal to the signal processing unit 21; the signal processing unit 21 performs corresponding amplification and other processing on the signal according to the hearing impairment condition of the patient and then outputs the signal to the actuator 22; the actuator 22 mechanically moves under the action of the driving electrical signal to drive the applied in-ear tissue. Finally, the vibration energy is input into the cochlea 19 in the inner ear through the oval window membrane 30 of the cochlea, achieving the hearing compensation objective. Compared with the traditional hearing aid for compensating the hearing impairment through sound excitation, the scheme of adopting mechanical excitation for the artificial middle ear has the advantages of no blockage of auditory canal, silent feedback, high voice definition, high-frequency gain and the like, and overcomes the defects of the traditional hearing aid.
The embodiment provides an acoustic excitation loudness calculation method based on a human ear loudness perception model, which comprises a model processing stage and a model processing rear-end stage, wherein the model processing stage comprises the following steps: the method comprises the following steps of 1, establishing a loudness perception model, wherein the method comprises an outer ear filter model, a middle ear dynamics model and a cochlea dynamics model; under acoustic excitation, the sound pressure at the free field sound source is converted into the sound pressure at the eardrum after passing through the external ear filter model; inputting sound pressure at the eardrum to the eardrum of the middle ear dynamics model to obtain cochlear fluid acceleration; and taking the cochlear fluid acceleration as the driving of a cochlear dynamics model, and calculating to obtain the basal membrane speed on each cochlear segment.
The model processing rear-end stage is the same as the method of the model processing rear-end stage in the following loudness perception model and the applied round window excitation loudness calculation method.
Referring to fig. 6, the embodiment provides a loudness perception model and an applied round window excitation loudness calculation method, where the loudness model in the embodiment can simulate acoustic excitation to verify the model by using acoustic excitation loudness data, and the main purpose of research is to calculate the round window excitation loudness. The method comprises a model processing stage and a model processing back-end stage, wherein the model processing stage comprises the following steps:
step 1: establishing a loudness perception model (external auditory Zhou Moxing) comprising an external ear filter model, a middle ear dynamics model and a cochlear dynamics model;
Step 2: inputting exciting force of a round window exciting artificial middle ear actuator to a round window membrane in a middle ear dynamics model in the constructed loudness perception model, and calculating to obtain cochlear fluid acceleration under round window excitation;
step 3: substituting the cochlear fluid acceleration into a cochlear dynamics model in the constructed loudness perception model, and calculating to obtain the basal membrane speed on each cochlear segment under round window excitation;
step 4: substituting the basal membrane speed of each cochlea segment into the data processing rear end in the constructed loudness perception model, and calculating to obtain the round window excitation loudness.
The outer ear filter model is:
Where P E is the sound pressure at the eardrum and P Free is the sound pressure at the free field source. n is the nth sample point of the time signal, k is the order of the filter, and a (k) is the gain parameter of the kth order filter.
The outer ear transfer function of the outer ear filter model is compared to standard ANSIS 3.4.4 as shown in figure 9. The outer ear transfer function of the present invention is quite compatible with standard ANSIS 3.4.4. The results show that the external ear filter model provided by the invention can accurately simulate the collection and resonance functions of the external ear in the process of transmitting sound pressure from a free field to the eardrum.
A schematic diagram of the middle ear dynamics model is shown in fig. 10, and a specific differential equation of motion is:
Wherein m M、mI、mS and m CF are respectively a malleus mass, an incus mass, a stapes mass and a cochlear fluid mass, k AML、kPIL、kAL、kE、kIMJ、kISJ and k RW are respectively a malleus anterior ligament stiffness, an incus posterior ligament stiffness, a stapedial annular ligament stiffness, an eardrum stiffness, an incus hammer joint stiffness, an incus stirrup joint stiffness and a round window membrane stiffness, c AML、cPIL、cAL、cE、cIMJ、cISJ、cVA、cCA and c RW are respectively a malleus anterior ligament damping, an incus posterior ligament damping, a stapedial annular ligament damping, an eardrum damping, an incus hammer joint damping, an incus stirrup joint damping, a vestibular aqueduct damping, a cochlear aqueduct damping and a round window membrane damping, a E is an eardrum area, and F RW is a force of a round window excitation type artificial middle ear on the round window membrane.
The middle ear transfer function and the stapes velocity of the middle ear dynamics model under acoustic excitation are compared with experimental data of Nakajima and the like and statistical experimental data of Koch and the like, respectively, as shown in fig. 11 and 12. The middle ear transfer function of the middle ear dynamics model under acoustic excitation is quite consistent with experimental data such as Nakajima, and the stapes speed under 94dB sound pressure level excitation is also in the range of statistical experimental data such as Koch. The result shows that the middle ear dynamics model can accurately simulate the sound transmission characteristics of the middle ear under acoustic excitation.
The round window excitation transfer function of the middle ear dynamics model was compared with experimental data such as Nakajima, etc., as shown in fig. 13. The round window excitation transfer function of the middle ear dynamics model is matched with experimental data such as Nakajima. The result shows that the middle ear dynamics model provided by the invention can simulate the sound transmission characteristics of human ears under round window excitation.
The cochlear dynamics model simplifies the cochlea to a one-dimensional fluid-coupled conical cochlea, as shown in fig. 14. The transfer of travelling waves in the cochlear dynamics model is described as:
Wherein p is the pressure difference across the cochlear septum, For radial acceleration in cochlear fluid, ρ is the density of cochlear fluid, H is the effective height of the scala vestibuli and scala tympani, and h=pi 2AC/(8WB).AC is the cross-sectional area of the cochlea, W B is the width of the basilar membrane.
The driving of the cochlear dynamics model is the pressure difference between the oval window membrane and the round window membrane.
The cochlear dynamics model divides the cochlea into 100 sections, each section is very similar in stress analysis, and the schematic diagram of the ith section of the cochlear dynamics model is shown in fig. 15. The motion differential equation of the ith section of the cochlear dynamics model is as follows:
Wherein m Bi、mRi and m Ti are respectively the base film mass, the net plate mass and the cover film mass on the i-th section, k Li、kBi、kOHCi、kHBi and k Ti are respectively the base film longitudinal coupling stiffness, the base film bending stiffness, the outer hair cell stiffness, the cilia bundle stiffness and the cover film stiffness, and c Li、cBi、cOHCi、cHBi and c Ti are respectively the base film longitudinal coupling damping, the base film bending damping, the outer hair cell damping, the cilia bundle damping and the cover film damping.
Further, the frequency selective characteristic and the frequency response characteristic of the basal membrane in the cochlear dynamics model are compared with experimental data as shown in fig. 16 and 17, respectively. The frequency selection characteristic curve of the basement membrane in the cochlear dynamics model is very consistent with experimental data such as Kringlebotn, and the frequency response characteristic of the basement membrane at the position 12mm away from the stapes is relatively consistent with experimental data such as Gundersen and the like and Stenfelt and the like. The result shows that the cochlear dynamics model can accurately simulate the sound transmission characteristics of a cochlea.
Further, the cochlear dynamics model contains an outer hair cell circuit model (as shown in fig. 18) to simulate the active amplification function of the cochlea caused by the outer hair cell electro-motion. The transmission of traveling waves in the cochlea causes displacement of the basal membrane, the reticular lamina and the covering membrane, further resulting in deflection of the cilia bundle and contraction of the outer hair cells; deflection of the fiber bundles and contraction of the outer hair cells respectively lead to generation of transduction current and piezoelectric current, so that the outer hair cells are caused to perform electrokinetic movement; the electrokinetic movement of the outer hair cells generates an active excitation force that further amplifies the vibration of the basement membrane.
Further, a cochlear model including an outer hair cell circuit model is generally called an active cochlear model, and a cochlear model not considering the outer hair cell active amplification is generally called a passive cochlear model. As shown in fig. 19, basal membrane displacement of the active model and the passive model of the present invention was compared with experimental data of live cochlea and dead cochlea of Johnstone, etc. The displacement of the basement membrane of the active model and the passive model is very consistent with experimental data such as Johnstone. The result shows that the external hair cell circuit model can accurately simulate the active amplification effect of the external hair cells, and the cochlear dynamics model can accurately simulate the movement of the basement membrane under different excitation amplitudes.
Further, the transduction current and the piezoelectric current in the outer hair cell circuit model are respectively:
Wherein, V EP and V OHC are respectively the resting potentials of the cochlear canal and the external hair cell, f is the characteristic frequency of the cochlear segment, ε is the piezoelectric coupling coefficient, G 1 is the cilia bundle conductivity, and θ is the mesh plate inclination angle.
Further, the internal potential of the outer hair cells in the outer hair cell circuit model is [ ]) And extracellular potential (/ >)) The method comprises the following steps of:
Wherein, R ML and R TL are respectively the grounding resistance of the worm pipe and the drum step, R a and R b are respectively the resistance of the top and the base of the outer hair cell, and C a and C b are respectively the capacitance of the top and the base of the outer hair cell.
Further, the active exciting force generated by the outer hair cell circuit model is that
Wherein N OHC is the number of outer hair cells per fragment.
The model processing back-end stage comprises the following steps: the basal membrane dormitory on each segment of the cochlea was absolute and time integrated to find the initial excitation:
Ei,0＝0
where E i,t is the initial excitation of the ith substrate film segment at time t, v i,t is the speed of the ith substrate film segment at time t, sampling frequency f s =200 kHz, time constant τ=15 ms.
The data processing back-end stage comprises the following steps: according to 1/3 octave, a cochlear segment with a characteristic frequency of 88.4-11313.7Hz is divided into 21 excited segments, and cochlear segments with characteristic frequencies of less than 88.4Hz and greater than 11313.7Hz are respectively used as one excited segment, and the cochlea is divided into 23 excited segments in total. The excitation on the x-th excitation segment (E x) can be calculated as:
wherein M is the number of cochlear fragments contained in the x-th excitation segment.
Further, excitation on the x-th excitation segment is translated to specific loudness on the x-th excitation segment by:
Where C x,αx and A x are constants for calculating specific loudness on the x-th excitation segment and are different in each excitation segment. Preferably, the values of these parameters are calculated using an adaptive particle swarm optimization algorithm, with the optimization objective being the equal-loudness curve in the international standard ISO 226. The pair of equal loudness curves of the loudness perception model of the present invention with international standard ISO 226 is shown in fig. 20.
Further, the specific loudness over all excitation segments is summed to give an initial loudness (L I):
See fig. 7-8; the data processing back-end stage comprises the following steps: converting the initial loudness L I to a loudness level L L according to the function S; the loudness level is defined as: the loudness level of sound is the sound pressure level of a 1000Hz pure tone excitation in the case of equal loudness. According to the definition above for the loudness level, the initial loudness (L I) of the loudness model of the present invention can be translated into a loudness level (L L): the function S is
LL＝52.45tanh(1.427(LI-0.68))+37.2；
According to the relationship between loudness and loudness level described in american standard ANSI S3.4, the loudness level L L is converted to loudness L according to the function P; the function P is:
L＝8×10-4(0.1LL+1.2)4.4。
The loudness of the bandwidth noise and the loudness of the pure tone under frequency domain masking of the loudness perception model of the present invention under acoustic excitation are compared with experimental data, respectively, as shown in fig. 21 and 22. According to the loudness perception model, the loudness of bandwidth noise under acoustic excitation is matched with experimental data such as Zwicker, and the loudness of pure tone under frequency domain masking is matched with the experimental data of Zwicker. The result shows that the loudness perception model can accurately calculate the loudness of bandwidth noise and the loudness of pure sound under frequency domain masking.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (9)
1. The loudness perception model comprises an outer ear filter model, a middle ear dynamics model and a cochlea dynamics model; the method is characterized by comprising a model processing stage and a model processing rear-end stage, wherein the model processing stage comprises the following steps of:
step 1: establishing an outer ear filter model, a middle ear dynamics model and a cochlea dynamics model;
Step 2: inputting exciting force of a round window exciting artificial middle ear actuator to a round window membrane in a middle ear dynamics model in the constructed loudness perception model, and calculating to obtain cochlear fluid acceleration under round window excitation;
step 3: substituting the cochlear fluid acceleration into a cochlear dynamics model in the constructed loudness perception model, and calculating to obtain the basal membrane speed on each cochlear segment under the excitation of the round window.
The model processing back-end stage comprises the following steps:
Step 4: absolute values of basal membrane velocities on each cochlear segment; integrating the cochlea in time to obtain initial excitation on each cochlea segment;
Step 5: dividing a cochlea into a plurality of excitation sections, wherein each excitation section comprises a plurality of cochlea segments, and averaging the initial excitation of the cochlea segments in each excitation section to obtain the excitation of each excitation section;
Step 6: converting the excitation of each excitation segment into a specific loudness of each excitation segment; summing the specific loudness of all the excitation segments to obtain initial loudness;
Step 7: converting the initial loudness L I to a loudness level L L according to the function S; the function S is L L＝52.45tanh(1.427(LI -0.68)) +37.2;
Step 8: according to the function P, converting the loudness level L L into loudness L; the function P is l=8×10 -4(0.1LL+1.2)4.4.
2. A method according to claim 1, wherein in step 1, the method of establishing a middle ear dynamics model is: the malleus, the incus, the stapes and the cochlea fluid are simplified into mass, the vestibular aqueduct and the cochlea aqueduct are simplified into damping, and the tympanic membrane, the anterior malleus ligament, the posterior incus ligament, the stapedial annular ligament, the anvil-hammer joint, the anvil-stirrup joint and the round window membrane are simplified into rigidity and damping; the model can simulate the sound transmission characteristics of human ears under acoustic excitation and round window excitation while having quick calculation.
3. The method according to claim 2, wherein in step 1, the method for building a cochlear dynamics model is: simplifying the cochlea into a one-dimensional fluidly coupled conical cochlea with a round window and an oval window; the cochlea is divided into 100 segments by the model, and each segment consists of basal membrane mass, reticular plate mass, covering membrane mass, basal membrane longitudinal coupling rigidity and damping, basal membrane bending rigidity and damping, external hair cell rigidity and damping, cilia bundle rigidity and damping and covering membrane rigidity and damping; the model can accurately calculate basal membrane velocities on each cochlear segment under acoustic excitation and round window excitation.
4. A method according to claim 3, wherein in step 1, a digital filter is used to model the outer ear filter, in particular:
where P E is the sound pressure at the eardrum, P Free is the sound pressure at the free field source, n is the nth sample point of the time signal, k is the order of the filter, and a (k) is the gain parameter of the kth order filter.
5. The method of claim 4, wherein in step 1, the differential equation of motion of the middle ear dynamics model is:
Wherein m M、mI、mS and m CF are respectively a malleus mass, an incus mass, a stapes mass and a cochlear fluid mass, k AML、kPIL、kAL、kE、kIMJ、kISJ and k RW are respectively a malleus anterior ligament stiffness, an incus posterior ligament stiffness, a stapedial annular ligament stiffness, an eardrum stiffness, an incus hammer joint stiffness, an incus stirrup joint stiffness and a round window membrane stiffness, c AML、cPIL、cAL、cE、cIMJ、cISJ、cVA、cCA and c RW are respectively a malleus anterior ligament damping, an incus posterior ligament damping, a stapedial annular ligament damping, an eardrum damping, an incus hammer joint damping, an incus stirrup joint damping, a vestibular aqueduct damping, a cochlear aqueduct damping and a round window membrane damping, a E is an eardrum area, and F RW is a force of a round window excitation type artificial middle ear on the round window membrane.
6. The method of claim 5, wherein in step 1, the cochlear dynamics model reduces the cochlea to a one-dimensional fluid-coupled conical cochlea, and the transfer of the traveling wave in the cochlear dynamics model is described as:
Wherein p is the pressure difference across the cochlear septum, Radial acceleration in cochlear fluid, ρ is the density of cochlear fluid, H is the effective height of vestibular and scala tympani, h=pi 2AC/(8WB);AC is the cross-sectional area of cochlea, and W B is the width of basal membrane;
The driving of the cochlear dynamics model is the pressure difference between the oval window membrane and the round window membrane;
The cochlea dynamic model divides the cochlea into 100 sections, and the stress analysis of each section is very similar to the differential equation of motion of the ith section of the cochlea dynamic model, which is as follows:
Wherein m Bi、mRi and m Ti are respectively the base film mass, the net plate mass and the cover film mass on the i-th section, k Li、kBi、kOHCi、kHBi and k Ti are respectively the base film longitudinal coupling stiffness, the base film bending stiffness, the outer hair cell stiffness, the cilia bundle stiffness and the cover film stiffness, and c Li、cBi、cOHCi、cHBi and c Ti are respectively the base film longitudinal coupling damping, the base film bending damping, the outer hair cell damping, the cilia bundle damping and the cover film damping.
7. The method of claim 6, wherein in step 4, the initial excitation is determined by absolute value and time integration of basal membrane dormitories on each segment of the cochlea: e i,0 = 0
Where E i,t is the initial excitation of the ith substrate film segment at time t, v i,t is the speed of the ith substrate film segment at time t, sampling frequency f s =200 kHz, time constant τ=15 ms.
8. The method according to claim 7, wherein in step5, according to 1/3 octave, the cochlea segments having characteristic frequencies of 88.4-11313.7Hz are divided into 21 excitation segments, and the cochlea segments having characteristic frequencies of less than 88.4Hz and greater than 11313.7Hz are respectively regarded as one excitation segment, and the cochlea is divided into 23 excitation segments in total; excitation E x on the x-th excitation segment was calculated as:
wherein M is the number of cochlear fragments contained in the x-th excitation segment.
9. The method of claim 8 wherein in step 6, the excitation on the x-th excitation segment is translated to a specific loudness on the x-th excitation segment by:
Wherein C x,αx and a x are constants for calculating specific loudness on the x-th excitation segment, and are different in each excitation segment; the specific loudness over all excitation segments is summed to give the initial loudness L I:
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