Vestibular function improvement device and vestibular function improvement method

Abstract

A vestibular function improvement device (100) according to the present invention comprises: a generation unit (1) that generates an electric signal that causes a vibration including a frequency component in the range of 450-1500 hertz; and an output unit (2) that outputs a stimulus on the basis of the electric signal. The stimulus outputted by the output unit (2) is transmitted to the vestibular system of the inner ear. According to the present invention, vestibular functions can be improved by stimulating the vestibular system of the inner ear.

Description

Vestibular function improvement device and vestibular function improvement method

[0001] The present invention relates to a vestibular function improving device and a vestibular function improving method that improve vestibular function by stimulating the vestibular system of the inner ear.

[0002] The inner ear is composed of the vestibular system (otolith organs and semicircular canals) and the cochlea. The vestibular system is the organ responsible for human balance. In particular, the otolith organs (utricle and saccule), which sense head tilt (gravitational acceleration) and linear acceleration, allow humans to maintain their sense of balance. Various studies have shown that any impairment of this balance function can cause dizziness. Furthermore, a decline in the vestibular balance function, or vestibular function, can lead to conditions other than dizziness, such as locomotive syndrome, and can also make healthy individuals more susceptible to car sickness, sea sickness, and alcohol sickness.

[0003] It is known that vestibular function can be improved by applying sound stimulation to the vestibular system to reduce dizziness. For example, Patent Document 1 describes a method in which a sound of a specific frequency (50 to 140 Hz) is generated as a sound stimulation at a specific volume level (70 to 85 decibels) to stimulate the otoliths of a patient suffering from dizziness, thereby improving the patient's dizziness.

[0004] International Publication No. 2019 / 230941

[0005] The present inventors have conducted extensive research into whether it is possible to provide a stimulation to the vestibular system of the inner ear that is more suitable for improving vestibular function, and have completed the present invention. That is, an object of the present invention is to provide a vestibular function improving device and a vestibular function improving method that can improve vestibular function by providing stimulation to the vestibular system of the inner ear.

[0006] First, the present invention provides a vestibular function improvement device comprising: a generator that generates an electrical signal that generates vibrations having frequency components in the range of 450 to 1500 Hz; and an output unit that outputs stimulation based on the electrical signal (Invention 1).

[0007] As a result of extensive research, the inventors have found that vestibular function can be improved by applying stimuli containing frequency components in the range of 450 to 1500 Hz. That is, according to the above invention (Invention 1), vestibular function can be improved by outputting stimuli containing frequency components in the range of 450 to 1500 Hz, which are suitable for improving vestibular function, and applying the stimuli to the vestibular system of the inner ear.

[0008] In the above invention (Invention 1), it is preferable that the stimulus output by the output section is transmitted to the vestibular system of the inner ear (Invention 2).

[0009] In the above inventions (Inventions 1 and 2), the stimulus may be a sound stimulus (Invention 3), or the stimulus may be a vibration stimulus (Invention 4).

[0010] In the above inventions (Inventions 1 to 4), the output section may output the stimulus as noise containing frequency components over a predetermined range (Invention 5).

[0011] In the above invention (Invention 5), it is preferable that the sound pressure level of the high frequency band of the noise is lower than the sound pressure level of the frequency band in the range of 450 to 1500 Hz (Invention 6). Also, in the above invention (Invention 6), the high frequency band may be a frequency band of 2000 Hz or higher (Invention 7).

[0012] In the above inventions (Inventions 5 to 7), the output section may output the stimulus in the form of brown noise or pink noise (Invention 8).

[0013] In the above invention (Invention 1), the stimulus may be a vibration stimulus, and the output unit may output the stimulus in the form of white noise (Invention 9).

[0014] In the above inventions (Inventions 1 to 9), the output unit may combine the stimulus with a sound different from the stimulus and output the combined stimulus (Invention 10).

[0015] Secondly, the present invention provides a method for improving vestibular function, comprising: generating an electrical signal that generates vibrations having frequency components in the range of 450 to 1500 Hz; outputting a stimulus based on the electrical signal; and transmitting the stimulus to the vestibular system of the inner ear (Invention 11).

[0016] According to the vestibular function improving device and method of the present invention, vestibular function can be improved by outputting stimuli containing frequency components in the range of 450 to 1500 Hz, which are suitable for improving vestibular function, and applying the stimuli to the vestibular system of the inner ear. The improvement of vestibular function leads to effects such as alleviating dizziness disorders such as benign paroxysmal positional vertigo, Meniere's disease, and vestibular neuritis, alleviating diseases and symptoms other than dizziness, such as symptoms of locomotive syndrome, and alleviating dizziness caused by car sickness, sea sickness, alcohol intoxication, etc., which can occur even in healthy individuals.

[0017] FIG. 1 is a schematic configuration diagram of a vestibular function improvement device according to a first embodiment. FIG. 2 is a diagram showing the configuration of a device main body of the vestibular function improvement device according to the same embodiment. FIG. 3 is a functional block diagram for explaining functions that play a major role in the device main body of the vestibular function improvement device according to the same embodiment. FIG. 4 is a schematic configuration diagram of a vestibular function improvement device according to a second embodiment. FIG. 5 is a diagram for explaining a method for evaluating the results of center of gravity sway measurement. FIG. 6 is a graph showing the results of experiment 1 for verifying the effects. FIG. 7 is a graph showing the results of experiment 2 for verifying the effects. FIG. 8 is a graph showing noise applied to the subject (part 1). FIG. 9 is a graph showing noise applied to the subject (part 2). FIG. 10 is a graph showing noise applied to the subject (part 3). FIG. 11 is a graph showing the results of experiment 12 for verifying the effects. FIG. 12 is a graph showing the results of experiment 13 for verifying the effects.

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are examples, and the present invention is not limited to these embodiments.

[0019] 1 , a vestibular function improvement device 100 according to this embodiment includes a device main body 1 for generating an electrical signal that generates vibrations containing frequency components in the range of 450 to 1500 Hz, and headphones 2 for outputting stimuli based on the electrical signal. In the vestibular function improvement device 100 of this embodiment, a subject whose vestibular function is to be improved wears the headphones 2, and stimuli are transmitted in the form of sound stimuli to the vestibular system of the subject's inner ear.

[0020] The device main body 1 is configured to generate an electrical signal that generates vibrations containing frequency components in the range of 450 to 1500 Hz. The device main body 1 is an example of a generating unit in the present invention, and may be, for example, a general-purpose personal computer, but is not limited to this, and may be a mobile information terminal such as a smartphone or tablet terminal, or a dedicated terminal device.

[0021] The electrical signal generated by device main body 1 may be a signal that generates vibrations corresponding to a pure tone having a specific frequency component in the range of 450 to 1500 Hz, or a signal that generates vibrations corresponding to a complex tone including at least a specific frequency component in the range of 450 to 1500 Hz. The complex tone including at least a specific frequency component in the range of 450 to 1500 Hz may be a combination of multiple pure tones, or may be noise including frequency components over a predetermined range.

[0022] As shown in FIG. 2, the device main body 1 includes a CPU 11, a memory unit 12, a RAM 13, a display processing unit 14, a display unit 15, an input unit 16, and a communication interface unit 17, and is provided with a bus 18 for transmitting control signals or data signals between each unit.

[0023] When power is applied to the device main body 1, the CPU 11 loads various programs stored in the storage unit 12 into the RAM 13 and executes them. In this embodiment, the CPU 11 reads and executes the programs stored in the storage unit 12, thereby realizing the functions of a data acquisition unit 41, a data generation unit 42, a data processing unit 43, and a signal transmission unit 44 (shown in FIG. 3 ), which will be described later.

[0024] The display processing unit 14 displays the display data provided by the CPU 11 on the display unit 15. The display unit 15 may be, for example, a liquid crystal display.

[0025] The input unit 16 has a group of buttons for accepting user operation inputs, and includes an interface circuit for recognizing the press (operation) input of each button and outputting it to the CPU 11, but a touch panel input method may also be adopted as the input unit 16.

[0026] The communication interface unit 17 is connected to an external device (not shown) that supplies sound data to the device main body 1, a sound collection microphone (not shown) that acquires sound data, and the like, and is configured to be able to acquire sound data from outside the device main body 1. In addition, the communication interface unit 17 is connected to the headphones 2, and is configured to be able to transmit an electrical signal that generates vibrations to the headphones 2.

[0027] The following describes the functions realized by the device main body 1 configured as described above. Fig. 3 is a functional block diagram for explaining the functions that play the main roles in the device main body 1 of this embodiment, which is composed of a data acquisition means 41, a data generation means 42, a data processing means 43, and a signal transmission means 44. Not all of these means are essential components of the device main body 1, and the functions of the device main body 1 can be changed as appropriate, such as by selectively providing the device main body 1 with any of the functions.

[0028] The data acquisition means 41 has a function of acquiring sound data from outside the device main body 1, and this function is realized, for example, as follows: When a data import instruction is input via the input unit 16, the CPU 11 of the device main body 1 imports sound data from an external device (not shown) or a sound collection microphone (not shown) connected to the communication interface unit 17, and stores the imported sound data in the storage unit 12. Note that the sound data may be noise, music, human or animal voices, environmental sounds, artificial sounds, or other sounds recorded in a digital file in a predetermined format, or may be data imported into the device main body 1 via a sound collection microphone or the like.

[0029] The data generating means 42 has a function of mechanically generating sound data within the device main body 1, and this function is realized, for example, as follows: When a data generation instruction is input via the input unit 16, the CPU 11 of the device main body 1 mechanically generates sound data of a pure tone having a specific frequency component or sound data of noise having a specific waveform, and stores the generated sound data of the pure tone or noise in the storage unit 12.

[0030] The data processing means 43 has a function of processing sound data stored in the storage unit 12, and this function is realized, for example, as follows. When an instruction to process sound data is input via the input unit 16, the CPU 11 of the device main body 1 selects sound data to be processed from the sound data stored in the storage unit 12, performs the processing instructed on the sound data, and stores the processed sound data again in the storage unit 12. The processing may be, for example, a process of synthesizing multiple sound data, a process of cutting a certain frequency band of the sound data, a process of attenuating a certain frequency band of the sound data, or a process of emphasizing a certain frequency band of the sound data. When instructing each processing, the waveform of the selected sound data may be displayed on the display unit 15, so that the user can operate the input unit 16 while checking the display unit 15.

[0031] The signal transmitting means 44 has a function of converting sound data into an electrical signal and transmitting it outside the device main body 1, and this function is realized, for example, as follows: When an instruction to convert sound data into an electrical signal and transmit it outside is input via the input unit 16, the CPU 11 of the device main body 1 selects sound data to be transmitted from the sound data (including both unprocessed and processed sound data) stored in the storage unit 12, converts the selected sound data into an electrical signal, and transmits it outside the device main body 1 from the communication interface unit 17.

[0032] The headphones 2 are electrically connected to the device main body 1 via a wired or wireless connection, and are configured to receive an electrical signal generated by the device main body 1 and output a stimulus based on the electrical signal. The headphones 2 are an example of an output unit in the present invention, and may be earphones, speakers, or other acoustic devices. The speakers may be stationary or portable, such as worn around the neck, or may be built into hearing aids, glasses, sunglasses, a chair, a pillow, a cochlear implant, or the like.

[0033] In this embodiment, the device main body 1 (electrical signal generator) and headphones 2 (stimulus output unit) that constitute the vestibular function improvement device 100 are physically separate, but they can also be realized as an integrated device. For example, the vestibular function improvement device may be realized using a smart device such as a smart speaker, or a dedicated vestibular function improvement device with a built-in speaker as an output unit may be developed, or the vestibular function improvement device may be realized as a hearing aid with a built-in mechanism for playing therapeutic stimuli. When the vestibular function improvement device 100 is realized as a hearing aid, the hearing aid picks up ambient sounds, processes the sounds to make them easier to hear for the wearer via earphones, and transmits them. However, sound stimuli to be synthesized with the sounds may be prepared in the hearing aid in advance or supplied from an external device, and the sound stimuli may be provided to the wearer along with the ambient sounds.

[0034] The sound stimulus output by the headphones 2 is sound containing frequency components in the range of 450 to 1500 Hz. The sound stimulus may be a pure tone having specific frequency components in the range of 450 to 1500 Hz, or a complex tone containing specific frequency components in at least the range of 450 to 1500 Hz. The complex tone containing specific frequency components in the range of at least 450 to 1500 Hz may be a combination of multiple pure tones, or may be noise containing frequency components across a predetermined range. By providing the subject with a sound stimulus containing frequency components in the range of 450 to 1500 Hz, the vestibular function of the subject can be improved.

[0035] Furthermore, when the sound stimulus is noise containing frequency components over a predetermined range, it is preferable that the sound pressure level in the high-frequency band of the noise is lower than the sound pressure level in the frequency band ranging from 450 to 1500 Hz. In particular, it is preferable that the sound pressure level in the high-frequency band of 2000 Hz or higher is lower than the sound pressure level in the frequency band ranging from 450 to 1500 Hz. Rather than applying noise containing high-frequency components as sound stimulus to the subject, applying noise from which high-frequency components have been removed or noise from which high-frequency components have been attenuated as sound stimulus to the subject will be more effective in improving the vestibular function of the subject.

[0036] There are various types of noise, including those found in nature and those generated mechanically. Noise with a constant power spectral density or one that attenuates or amplifies depending on frequency is generally referred to as colored noise, designated by various color names. Noise with the same intensity (power spectral density) across all frequency bands is called white noise. In contrast to white noise, noise that attenuates in the high-frequency band is called pink noise (power spectral density inversely proportional to frequency) or brown noise (power spectral density inversely proportional to the square of frequency). Meanwhile, noise that amplifies in the high-frequency band is called blue noise (power spectral density proportional to frequency) or purple noise (power spectral density proportional to the square of frequency).

[0037] Examples of noises that have a high effect of improving vestibular function include brown noise and pink noise, which have a sound pressure level in the high-frequency band that is lower than the sound pressure level in the frequency band between 450 and 1500 Hz. Brown noise, in particular, is more pleasant to listen to than pure tone, reducing the stress experienced by the patient during treatment. Furthermore, even white noise that has been processed to cut out the high-frequency band has been shown to have a high effect of improving vestibular function.

[0038] The frequency at which the attenuation starts may also be set arbitrarily. For example, the noise may have a constant power spectral density on the frequency side lower than 100 Hz, and the power spectral density may attenuate on the high frequency side. Setting the frequency at which the attenuation starts can be expected to add a sense of comfort.

[0039] Furthermore, the noise is not limited to brown noise or pink noise, but may be noise whose exponent is a decimal, such as noise whose power spectrum density is inversely proportional to the 1.5th power of frequency. Specifically, noise whose exponent is 0.5 or 2.5 may be considered.

[0040] In addition to the noise that attenuates according to the frequency rule as described above, the noise may be noise in which one or more frequency bands of any width are attenuated or band-cut processed, or noise that attenuates in a step-like manner with each step width set to an arbitrary value for each predetermined frequency, or noise with frequency characteristics that are generated to draw a free curve, for example, along the frequency characteristics of the human audible range.

[0041] The use of pure tones or noise alone as sound stimuli may be painful for some recipients. Therefore, for example, pleasant sounds such as music or environmental sounds may be synthesized with sounds containing frequency components in the 450 to 1500 Hz range, and the processed sound stimuli may be provided to the recipient. Such synthesized sound stimuli allow the recipient to receive the sound stimuli more comfortably.

[0042] The sound pressure level of the sound stimulation output by the headphones 2 is not particularly limited, but is preferably in the range of 10 decibels or more and less than 70 decibels, and more preferably in the range of 20 decibels or more and less than 50 decibels. If the sound pressure level is less than 10 decibels, a sufficient therapeutic effect cannot be obtained, and if the sound pressure level is greater than 70 decibels, the stimulation is not only painful for the patient but may also cause hearing loss in some cases.

[0043] The duration of stimulation of the recipient by the sound stimulation output by the headphones 2 is not particularly limited, but is preferably between 30 seconds and 60 minutes, and more preferably between 1 and 10 minutes. If the stimulation duration is less than 30 seconds, the duration of the therapeutic effect (carryover effect) is short, and sufficient therapeutic effect cannot be obtained. Furthermore, if the stimulation duration is longer than 60 minutes, although there is a therapeutic effect, no significant increase in the carryover effect is confirmed, and further extension of the duration is not expected to be effective. Furthermore, there is a risk of longer restraint time and increased burden on the recipient.

[0044] The procedure for performing a treatment to improve vestibular function on a patient (e.g., a vertigo sufferer) using the vestibular function improvement device 100 configured as described above will now be described. First, a treatment provider (e.g., a caregiver such as a physician) powers on the device main unit 1 of the vestibular function improvement device 100 and has the patient wear headphones 2. Next, the treatment provider operates the device main unit 1 to output sound stimuli containing frequency components in the 450-1500 Hz range suitable for the patient from the headphones 2. By listening to the output sound, the patient's vestibular function is activated, and, for example, if the patient suffers from vertigo, the vertigo is alleviated. Note that the sound stimuli may be output continuously for a predetermined period of time, or may be output intermittently in multiple intervals. The conditions for presenting the sound stimuli may be determined appropriately based on the patient's disease, symptoms, severity of symptoms, and purpose of the stimuli. Alternatively, the patient may operate the vestibular function improvement device 100 as the treatment provider.

[0045] 4 , a vestibular function improvement device 200 according to this embodiment includes a device main body 1 for generating an electrical signal that generates vibrations containing frequency components in the range of 450 to 1500 Hz, and bone conduction earphones 3 for outputting stimuli based on the electrical signal. In the vestibular function improvement device 200 according to this embodiment, a patient wears the bone conduction earphones 3, and the stimulation is transmitted in the form of vibration stimulation to the vestibular system of the patient's inner ear. Note that the device main body 1 is the same as that constituting the vestibular function improvement device 100 according to the first embodiment, and therefore a description thereof will be omitted here.

[0046] The bone conduction earphones 3 are electrically connected to the device main body 1 via a wired or wireless connection and are configured to receive electrical signals generated by the device main body 1 and output stimuli based on the electrical signals. The bone conduction earphones 3 are an example of an output unit in the present invention, and transmit vibrations directly to the inner ear by applying vibrations to the ear and its surrounding area. The output unit for transmitting the vibration stimuli may also be a device that applies vibrations by contacting any part of the head of the recipient other than the ear, such as the mandible, nasal bone, mastoid process, or teeth. In this case, a device shaped like glasses, a hairband, or headgear may be used. Alternatively, the device may incorporate a vibrator. The vibrator may be built into a hearing aid, glasses, sunglasses, chair, pillow, cochlear implant, or the like. If vibration stimuli could be applied to the recipient without blocking their ears, the recipient's vestibular function could be improved while listening to external sounds.

[0047] The vibration stimulus output by the bone conduction earphones 3 is sound vibration containing frequency components in the range of 450 to 1500 Hz. The vibration stimulus may be a pure tone vibration having a specific frequency component in the range of 450 to 1500 Hz, or a complex tone vibration containing at least a specific frequency component in the range of 450 to 1500 Hz. The complex tone vibration containing at least a specific frequency component in the range of 450 to 1500 Hz may be a combination of multiple pure tone vibrations, or may be noise vibration containing frequency components over a predetermined range. By providing the recipient with a vibration stimulus containing frequency components in the range of 450 to 1500 Hz, the recipient's vestibular function can be improved.

[0048] Furthermore, when the vibration stimulus is noise vibrations containing frequency components over a predetermined range, it is preferable that the sound pressure level of the high-frequency band of the noise is lower than the sound pressure level of the frequency band ranging from 450 to 1500 Hz. In particular, it is preferable that the sound pressure level of the high-frequency band of 2000 Hz or higher is lower than the sound pressure level of the frequency band ranging from 450 to 1500 Hz. The effect of improving the vestibular function of the patient is greater when noise from which high-frequency components have been removed or noise with attenuated high-frequency components is applied as the vibration stimulus to the patient, rather than when noise containing high-frequency components is applied as the vibration stimulus to the patient.

[0049] Examples of noises that have a high effect of improving vestibular function include brown noise and pink noise, which have a sound pressure level in the high frequency range lower than the sound pressure level in the frequency range of 450 to 1500 Hz. It has also been confirmed that even white noise, which has been processed to cut out the high frequency range, has a high effect of improving vestibular function.

[0050] Furthermore, when vibration stimulation was administered to the patient, unlike sound stimulation, even white noise that had not been processed to cut out high frequencies was found to have a certain degree of effect in improving vestibular function. This is thought to be because the propagation path of bone conduction is complex, and high frequencies are attenuated by skin and bone tissue as the vibration reaches the inner ear, resulting in the vibration stimulation being transmitted to the inner ear as noise with frequency characteristics similar to Brownian noise.

[0051] The procedure for performing a treatment to improve vestibular function on a recipient (e.g., a vertigo sufferer) using the vestibular function improvement device 200 configured as described above will now be described. First, a treatment provider (e.g., a physician or other caregiver) powers on the device main unit 1 of the vestibular function improvement device 200 and has the recipient wear the bone conduction earphones 3. Next, the treatment provider operates the device main unit 1 to output vibrational stimuli from the bone conduction earphones 3, which are generated by converting sound containing frequency components in the 450 to 1500 Hz range into vibrations appropriate for the recipient. The output vibrations are transmitted to the recipient's vestibular system, activating the recipient's vestibular function. For example, if the recipient suffers from vertigo, the vertigo is alleviated. Note that the vibrational stimuli may be output continuously for a predetermined period of time, or may be output intermittently in multiple increments with intervals in between. The conditions for presenting the vibrational stimuli may be determined appropriately based on the recipient's disease, symptoms, the severity of the symptoms, the purpose of the stimuli, and the like. Furthermore, the person receiving treatment may operate the vestibular function improvement device 200 as the person providing treatment.

[0052] Although the vestibular function improving device and method according to the present invention have been described above with reference to the drawings, the present invention is not limited to the above-described embodiments and various modifications are possible. For example, the number of stimuli applied to the person receiving treatment does not have to be one, and both sound stimuli and vibration stimuli may be applied to the person receiving treatment simultaneously, or sound stimuli may be applied first, followed by vibration stimuli after a predetermined time has elapsed.

[0053] <Various Experiments and Evaluation Results> The inventors conducted various experiments to verify and confirm that outputting the above-described stimuli using the vestibular function improvement devices 100 and 200 and applying the stimuli to the vestibular system of the inner ear has the effect of improving vestibular function. The various experiments conducted by the inventors and the results of their evaluations are described below.

[0054] (Evaluation Method) Diagnosing dizziness and balance disorders generally involves measuring center of gravity sway using a stabilometer. As shown in FIG. 5( a), the results of center of gravity sway measurement using a stabilometer are displayed as a line tracing the trajectory of center of gravity sway. Quantitative evaluation is typically performed using the length of the line (total trajectory length) drawn as the trajectory or the area enclosed by a perimeter set to surround the line (perimeter area, see FIG. 5( b)). However, previous evaluation methods have sometimes included trajectories of sway unrelated to dizziness, such as those due to temporary unsteadiness immediately after the start of measurement, making it difficult to properly evaluate the effectiveness. Therefore, the present inventors adopted an evaluation method that introduces a new evaluation index that focuses on the set density of the point cloud (plots) constituting the traced trajectory.

[0055] As an example of a new evaluation index focusing on the aggregation density of the point cloud (plots) constituting the drawn trajectory, the area of ​​an approximate circle (90% approximate circle area) that represents 90% of the total number of plots, with the center of gravity of the plots constituting the drawn trajectory as its center, can be calculated and used (see FIG. 5( c)). The 90% approximate circle area can be calculated as follows: (1) Calculate the central coordinates of a rectangle (the center of gravity of the trajectory) consisting of the width (the length between the minimum and maximum values ​​on the x-axis coordinate) and height (the length between the minimum and maximum values ​​on the y-axis coordinate) of the trajectory of center of gravity sway. (2) Calculate the distance from the center of gravity for each plot. (3) Sort the plots in order of shortest distance from the center of gravity. (4) Extract the plots corresponding to 90% of the total number of plots. (5) Calculate the area of ​​a circle whose radius is from the extracted plot to the center of gravity and whose center is the coordinate of the center of gravity.

[0056] Note that the new evaluation index used for the evaluation is not limited to the above-mentioned 90% approximate circle area, as long as it is based on the aggregate density of the group of points (plots) that make up the drawn trajectory. For example, the plots to be evaluated may be extracted based on the variance or standard deviation of the distance from the center of gravity of the plots, and the area of ​​a circle defined based on those plots may be calculated, or an ellipse approximation (the area of ​​an ellipse may be calculated).

[0057] (Experimental Method) In various experiments conducted to confirm the effects of the present invention, center of gravity sway was measured using a stabilometer. The stabilometer used was a specially designed, home-made device with load sensors placed at the four corners of the examination table. The sampling frequency for center of gravity sway was 60 Hz, and 3,600 plots of data were acquired per minute. The experimental methods used were either a rotational stress test (similar to that described in Patent Document 1), in which the subject is seated in a rotating chair and stimulated while the chair is rotating, or a rubber stress test, a type of center of gravity sway measurement performed clinically. In the rotational stress test, a specially designed, home-made rotating plate rotating at a constant speed (12 rpm) was used as the rotation mechanism for applying the rotational load to the subject. In the rubber stress test, foam rubber (manufactured by 5 Billion Fitness) was set on the examination table of the stabilometer.

[0058] Body balance during upright standing is maintained by inputs from the sense of balance (vestibular sensation), vision, and somatosensory sense, which are processed by the central nervous system and output to the skeletal muscles of the limbs and trunk. Evaluation of body balance during upright standing is performed by applying a load to one or more of the input systems of the sense of balance (vestibular sensation), vision, and somatosensory sense. The inventors employed the rotational load test method and the rubber load test method described above to evaluate the dizziness reduction effect of stimulation.

[0059] After providing sufficient explanation to the subjects and obtaining their consent, the effects of vestibular stimulation were evaluated. Two test methods were used, as shown below, and the method was selected based on the subjects' ages and preferences.

[0060] The rotational stress test induces temporary dizziness due to the rotational stress, making it easier for the patient to feel the effects of the dizziness treatment. However, it is important to note that the temporary dizziness caused by the rotational stress gradually subsides over time. Because the sensation of temporary dizziness and the time it takes for it to subside are easily affected by the patient's physical condition and diurnal fluctuations, dividing the results of the center of gravity sway measurement before and after the rotational stress eliminates the influence of the patient's physical condition and diurnal fluctuations. For this reason, the test must be conducted twice, with and without the stimulation, and a sufficient interval must be allowed until the next measurement to eliminate the possibility that temporary dizziness caused by the rotational stress will affect the next measurement, making the evaluation time-consuming. Furthermore, the rotational stress can be quite burdensome for some patients, and even healthy patients with impaired vestibular function due to aging or other factors may experience persistent nausea symptoms (e.g., headaches and nausea) after the rotational stress test.

[0061] The rubber load test method allows for simple and quick evaluation. It does not require the large-scale equipment required for the rotational load test method, which applies a rotational load to the subject. Furthermore, because the load is applied only while the subject is standing on the rubber during measurement, the burden on the subject is extremely small.

[0062] The rotational load test was conducted using the following procedure. First, the subject (recipient) sat on the stabilometer and measured their center of gravity for one minute while standing with their eyes and legs closed (Procedure A1). The 90% approximate circle area was calculated for the pre-rotation load measurement results obtained in Procedure A1 (Procedure A2). Next, the subject was given a one-minute rest (Procedure A3). Subsequently, the subject sat on the rotation mechanism and a one-minute rotation load was applied (Procedure A4). The subject was again asked to sit on the stabilometer and measured their center of gravity for one minute while standing with their eyes and legs closed (Procedure A5). The 90% approximate circle area was calculated for the pre-rotation load measurement results obtained in Procedure A5 (Procedure A6). After an interval of at least 30 minutes, Procedures A1 to A6 were repeated (Procedures B1 to B6). In Procedure B3, which corresponds to Procedure A3, the one-minute rest period was not provided; instead, the subject was stimulated for one minute by the vestibular function improvement device. Therefore, A6 gives the 90% approximate circle area after rotational load when no stimulation is applied, and B6 gives the 90% approximate circle area after rotational load when stimulation is applied. X1 is the value obtained by dividing the 90% approximate circle area obtained in A6 by the 90% approximate circle area obtained in A2. Similarly, X2 is the value obtained by dividing the 90% approximate circle area obtained in B6 by the 90% approximate circle area obtained in B2. Furthermore, the value obtained by dividing X2 by X1 indicates the degree of dizziness, and will be referred to as the sway area ratio hereinafter. A sway area ratio smaller than 1 indicates a dizziness-reducing effect, and a ratio larger than 1 indicates that dizziness has worsened.

[0063] On the other hand, the rubber load test method experiment was conducted as follows: First, the subject (recipient) stood on the stabilometer equipped with the foam rubber and measured their center of gravity for one minute while standing with their eyes and legs closed (Procedure C1). The 90% approximation circle area was calculated for the pre-rotation load measurement results obtained in Procedure C1 (Procedure C2). Next, the subject was stimulated for one minute using the vestibular function improvement device (Procedure C3). Next, the subject was again asked to stand on the stabilometer equipped with the foam rubber and measured their center of gravity for one minute while standing with their eyes and legs closed (Procedure C4). The 90% approximation circle area was calculated for the pre-rotation load measurement results obtained in Procedure C4 (Procedure C5). The 90% approximation circle area obtained in C5 divided by the 90% approximation circle area obtained in C2 was defined as Y1. Y1 indicates the degree of dizziness, and will be referred to as the sway area ratio hereafter. The sway area ratio was evaluated in the same manner as in the rotation load test method.

[0064] In this way, the same indicator, the swing area ratio, is used in both the rotational load test method and the rubber load test method, which allows the therapeutic effect to be evaluated equally in both test methods.

[0065] (Experiment 1) Following the experimental procedure (rotational load test method) described above, a signal was generated using a vestibular function reduction device to generate vibrations corresponding to pure tones with frequency components in 100-Hz increments in the range of 100 to 1000 Hz, and sound stimuli based on this signal were presented to a subject (healthy individual, n=1) via headphones (Audio-Technica, model number: ATH-WS990BT). The results are shown in Table 1. Figure 6 shows a graph of the results of Table 1, with frequency on the horizontal axis and vibration area ratio on the vertical axis.

[0066]

[0067] As shown in Table 1 and FIG. 6, in addition to the 100 Hz pure tone, which is known as a known technique to have a dizziness-reducing effect, the pure tone in the range of 500 to 700 Hz was also found to be effective.

[0068] (Experiment 2) Using the above-described experimental procedure (rubber load test method), a vestibular function improvement device was used to generate signals that generated vibrations corresponding to pure tones with frequency components in the range of 400 to 800 Hz, with 25 Hz increments for frequencies below 500 Hz and above 700 Hz, and 100 Hz increments for frequencies between 500 and 700 Hz. Sound stimuli based on these signals were presented to a subject (healthy individual, n=1) via headphones (same as above). The results are shown in Table 2. Figure 7 shows the results of Table 2 plotted as a graph, with frequency on the horizontal axis and sway area ratio on the vertical axis.

[0069]

[0070] As shown in Table 2 and FIG. 7, a clear effect was observed for pure tones in the range of 450 to 750 Hz, and a slight improvement was also observed for pure tones of 775 Hz.

[0071] (Experiment 3) Experiments 1 and 2 were conducted using a single healthy subject, so the results may not reflect individual differences. Previous research on vestibular stimulation using the Vestibular Evoked Myogenic Potential (VEMP) test has reported that, for example, in patients with Meniere's disease, the frequency (characteristic frequency) highly responsive to vestibular stimulation shifts toward higher frequencies. It has also been reported that the otolith layer involved in vestibular stimulation undergoes morphological changes, such as enlargement of the otoliths, with aging. Based on these reports, the following experiment was conducted on five subjects of different ages and with or without ear disease to confirm whether there were individual differences in the characteristic frequency observed in Experiments 1 and 2.

[0072] Following the experimental procedure (rubber load test method) described above, the vestibular function improvement device was used to generate a signal that generates vibrations corresponding to pure tones with frequency components in 500-Hz increments in the range of 500 to 2000 Hz, and sound stimuli based on this signal were presented to the subjects via headphones (same as above). The results are shown in Table 3. Subject 5 was a patient with ear disease (patulous Eustachian tube, viral hearing loss).

[0073]

[0074] As shown in Table 3, there were individual differences in the frequency range where the sway area ratio was below 1, i.e., where there was a therapeutic effect. Furthermore, there were individual differences in the frequency range where the therapeutic effect was greatest (highlighted in bold in Table 3), with a clear shift to higher frequency bands mainly due to age. It is believed that the therapeutic effect is particularly strong in patients with dizziness in the higher frequency bands. Therefore, it is believed that it would be more effective to adjust the frequency range and sound pressure level of the therapeutic stimulation applied appropriately according to the condition of the patient.

[0075] Thus, the frequency range with the most therapeutic effect varied from person to person, and this range was 450 to 1500 Hz. It was confirmed that it is important for therapeutic stimuli to include frequency components in this range.

[0076] (Experiment 4) While conducting experiments in which subjects were given stimuli containing various frequency components, the inventors discovered the possibility that high-frequency components attenuated the effects of vestibular function improvement. In other words, high-frequency components had a negative impact on the vestibular function improvement effect. To confirm this, following the experimental procedure described above, a vestibular function improvement device was used to generate a stimulus sound composed of a pure tone with a 100 Hz frequency component, which is effective in improving vestibular function, and a pure tone with a 600 Hz frequency component, which is also effective in improving vestibular function. This stimulus sound was then further synthesized with a pure tone with a high-frequency component (non-effective frequency) to generate a signal that generated corresponding vibrations. Sound stimuli based on this signal were then presented to subjects (healthy subjects, n = 2) via headphones (same as above). Multiple experiments were conducted, varying the frequency of the high-frequency component from 2000 Hz to 8000 Hz. Subject 1 was tested using a rotational load test, and subject 4 was tested using a rubber load test. The results are shown in Table 4.

[0077]

[0078] As shown in Table 4, for subject 1, when no pure tone with a non-effective frequency was added, the sway area ratio was 0.16, indicating that the stimulation sound synthesized from a 100 Hz pure tone and a 600 Hz pure tone had a significant effect on improving vestibular function. However, when a pure tone with a non-effective frequency in the high frequency band above 2000 Hz was added, the sway area ratio increased with increasing frequency, indicating that the effect on improving vestibular function was attenuated. In particular, when a pure tone with a non-effective frequency of 8000 Hz was added, it was found that the wobble caused by the rotational load worsened compared to before the stimulation sound synthesized from a 100 Hz pure tone and a 600 Hz pure tone was added.

[0079] For subject 4, the sway area ratio was 0.86 when no pure tone with an ineffective frequency was added, but when a pure tone with an ineffective frequency in the high frequency band above 4000 Hz was added, the sway area ratio increased, indicating a decrease in the effect of improving vestibular function. In particular, when a pure tone with an ineffective frequency of 8000 Hz was added, not only was the effect of improving vestibular function lost, but the dizziness worsened.

[0080] Thus, the results of Experiment 4 confirmed that even when subjects were given sound stimuli containing effective frequency components that have the effect of improving vestibular function, sound stimuli containing frequency components in the high frequency band above 2000 Hz attenuated the effect of improving vestibular function.

[0081] Up to this point, we have evaluated the effect of improving vestibular function (reduction of dizziness) by applying sound stimuli using headphones, but we also conducted a similar evaluation of the effect of improving vestibular function by applying vibration stimuli using bone conduction earphones, and confirmed that the frequency range showing the effect of improving vestibular function is the same.

[0082] (Experiment 5) Following the experimental procedure (rotational load test method) described above, a vestibular function improvement device was used to create the Brownian noise shown in Figure 8 and a noise source with a partial frequency band of Brownian noise attenuated. A signal generating vibrations corresponding to the noise was generated, and sound stimuli based on the signal were presented to a subject (healthy individual, n = 1) via headphones (Audio-Technica, model number: ATH-WS990BT). Figure 8 is a semi-logarithmic graph with sound pressure level on the vertical axis and frequency on the horizontal axis. (a) represents Brownian noise, (b) represents Brownian noise with the 40-150 Hz frequency band cut, (c) represents Brownian noise with the 400-800 Hz frequency band cut, and (d) represents Brownian noise with the 40-150 Hz frequency band and the 400-800 Hz frequency band cut. The experimental results are shown in Table 5.

[0083]

[0084] As shown in Table 5, the effect of improving vestibular function was confirmed even when subjects were given sound stimulation of Brownian noise, which is noise containing specific frequency components in the range of at least 450 to 1500 Hz. It can be seen that band-cut processing is effective whether it cuts the 40 to 150 Hz frequency band of Brownian noise or the 400 to 800 Hz frequency band of Brownian noise, but cutting both the 40 to 150 Hz and 400 to 800 Hz frequency bands of Brownian noise eliminates the effect of improving vestibular function.

[0085] (Experiment 6) Following the experimental procedure (rotational load test method) described above, signals were generated using a vestibular function improvement device to generate vibrations corresponding to the purple noise, blue noise, and white noise shown in Figure 9, and sound stimuli based on these signals were given to a subject (healthy individual, n=1) via headphones (manufactured by Audio-Technica, model number: ATH-WS990BT). Figure 9 is a semi-logarithmic graph with sound pressure level on the vertical axis and frequency on the horizontal axis, where (a) represents purple noise, (b) represents blue noise, and (c) represents white noise. The experimental results are shown in Table 6.

[0086]

[0087] As shown in Table 6, when subjects were given purple noise, blue noise, or white noise with a high sound pressure level in the frequency band above 2000 Hz, even if the noise contained specific frequency components in the range of 450 to 1500 Hz, no effect on improving vestibular function was confirmed. This confirms that when giving subjects sound stimulation with noise, it is preferable to give noise with a lower sound pressure level in the frequency band above 2000 Hz than in the frequency band between 450 and 1500 Hz.

[0088] (Experiment 7) In Experiment 5, signals were generated to generate vibrations corresponding to the Brownian noise shown in Figure 8 and noise obtained by cutting a portion of the frequency band of the Brownian noise using band-cut processing, and sound stimuli based on these signals were given to the subject. To provide the noise shown in Figure 8 as a vibration stimulus, bone conduction earphones (Aeropex, manufactured by Aftershokz) were connected to the vestibular function improvement device instead of headphones, and the vibration stimulus was given to the subject (healthy subject, n = 1). The results of the experiment are shown in Table 7.

[0089]

[0090] As shown in Table 7, experimental results similar to those obtained with sound stimulation were obtained when vibration stimulation was used instead of sound stimulation. That is, the effect of improving vestibular function was confirmed even when subjects were given sound stimulation of Brownian noise, which is noise containing specific frequency components at least in the range of 450 to 1500 Hz. It can be seen that band-cut processing is effective whether it cuts the 40 to 150 Hz frequency band of Brownian noise or the 400 to 800 Hz frequency band of Brownian noise. However, it can be seen that cutting both the 40 to 150 Hz and 400 to 800 Hz frequency bands of Brownian noise eliminates the effect of improving vestibular function.

[0091] (Experiment 8) In Experiment 6, signals were generated to generate vibrations corresponding to the purple noise, blue noise, and white noise shown in Figure 9, and sound stimuli based on these signals were given to the subject. This experiment confirmed the effect of giving these signals as vibration stimuli. As in Experiment 7, instead of headphones, bone conduction earphones (Aeropex, manufactured by Aftershokz) were connected to the vestibular function improvement device, and a subject (healthy individual, n = 1) was given vibration stimuli based on the noise shown in Figure 9. The results of the experiment are shown in Table 8.

[0092]

[0093] As shown in Table 8, when subjects were given purple noise vibration stimuli with high sound pressure levels in the frequency range above 2000 Hz, even noise containing specific frequency components in the 450-1500 Hz range, no improvement in vestibular function was observed, as was the case with sound stimuli. On the other hand, when subjects were given white noise or blue noise as sound stimuli, no improvement in vestibular function was observed (Experiment 6-2), but when they were given as vibration stimuli, improvements in vestibular function were confirmed. In other words, when subjects were given vibration stimuli whose power spectral density was proportional to the frequency (blue noise) to the square of the frequency (purple noise), it was found to be effective in improving vestibular function. This is thought to be due to the complex propagation path of bone conduction, and the attenuation of high-frequency bands by skin and bone tissue during the vibration transmission to the inner ear. As a result, white noise transmits vibration stimuli to the inner ear as noise with frequency characteristics similar to Brownian noise.

[0094] (Experiment 9) In Experiment 7, vibration stimuli based on the Brownian noise shown in Figure 8(a) were applied to the front of the ear using bone conduction earphones, but we also wanted to confirm the effects of applying vibrations by contact with other parts of the body (mandible, nasal bone, mastoid process, parietal region). The bone conduction earphones used in Experiment 7 were connected to a vestibular function improvement device, and a subject (healthy individual, n = 1) was given vibration stimuli based on the noise shown in Figure 8(a). The results of the experiment are shown in Table 9.

[0095]

[0096] As shown in Table 9, even when vibrations were applied to the mandible, nasal bone, mastoid process, and parietal area, the same effect was observed as when vibration stimulation was applied to the anterior part of the ear using bone conduction earphones.

[0097] (Experiment 10) Following the experimental procedure (rotational load test method) described above, a vestibular function improvement device was used to generate a signal that generates vibrations corresponding to the processed white noise shown in Figure 10. Sound stimuli based on this signal were then presented to a subject (healthy individual, n = 1) via headphones (Audio-Technica, model number: ATH-WS990BT). Figure 10 is a semi-logarithmic graph with sound pressure level on the vertical axis and frequency on the horizontal axis. (a) shows white noise with the frequency band above 2000 Hz cut using band-cut processing. (b) shows white noise with the sound pressure levels emphasized in both the 50-140 Hz and 500-700 Hz frequency bands. (c) shows white noise with the sound pressure levels attenuated in the order of 150-450 Hz, 450-1500 Hz, and 1500 Hz and above. The experimental results are shown in Table 10.

[0098]

[0099] As shown in Table 10, even when white noise was given to the subject as a sound stimulus, the effect of improving vestibular function was confirmed by processing to cut frequency bands above 2000 Hz, processing to emphasize effective frequency bands (50 to 140 Hz and 500 to 700 Hz), and processing to attenuate high frequency bands in a stepped manner.

[0100] (Experiment 11) Following the experimental procedure (rotational load test method) described above, a vestibular function improvement device was used to provide a sound stimulus obtained by synthesizing the Brownian noise shown in FIG. 8(a) with classical music (Chopin, Nocturne op. 9-2) to a subject (healthy individual, n=1) via headphones (Audio-Technica, model number: ATH-WS990BT). For comparison, an experiment was also conducted in which sound stimuli based on classical music without Brownian noise were provided. The experimental results are shown in Table 11.

[0101]

[0102] As shown in Table 11, when the test subjects were given sound stimulation of music alone, no sufficient effect of reducing dizziness was confirmed, but when the test subjects were given sound stimulation of music synthesized with Brownian noise, an effect was confirmed.

[0103] (Experiment 12) Following the experimental procedure (rubber load test method) described above, a signal generating vibrations corresponding to the Brownian noise shown in Figure 8(a) was generated using a vestibular function improvement device, and sound stimuli based on this signal were applied to a subject (healthy individual, n = 1) via headphones (Audio-Technica, model number: ATH-WS990BT). In Procedure B2, the duration of stimulation applied to the subject using the vestibular function improvement device was varied from 1 minute, 5 minutes, 10 minutes, 30 minutes, to 60 minutes to examine the effects of varying stimulation duration. Furthermore, in Procedure B3, center of gravity sway measurements were performed every 30 minutes starting immediately after stimulation application to examine the duration of the stimulation effect. The results of the experiment are shown in Figure 11, plotted as a graph with measurement time on the horizontal axis and sway area ratio on the vertical axis. Measurements were performed three times, and the average values ​​are shown in Figure 11.

[0104] As shown in Figure 11, a tendency was confirmed that the longer the stimulation time, the longer the duration of the effect. When the stimulation time was 1 minute, the measurement results were already equivalent to those when no stimulation was given 30 minutes after stimulation. However, when the stimulation time was 5 minutes or longer, the effect continued even 1 hour after stimulation. When the stimulation time was 30 or 60 minutes, the effect was confirmed to be continuing even more than 2 hours after stimulation. However, when the stimulation time was 10 minutes or longer, a significant increase in the duration of the effect was not expected, and considering the significant burden on the patient, such as physical and time constraints, it is not believed that a longer stimulation time is necessarily better.

[0105] (Experiment 13) Following the experimental procedure (rubber load test method) described above, a signal generating vibrations corresponding to the Brownian noise shown in Figure 8(a) was generated using a vestibular function improvement device, and sound stimuli based on this signal were presented to a subject (healthy individual, n = 1) via headphones (Audio-Technica, model number: ATH-WS990BT). Here, the center of gravity sway measurement in Procedure B3 was performed every 30 minutes starting immediately after the stimulation. If the measurement results were equivalent to those without stimulation, another 1-minute stimulation was administered before the next 30-minute measurement. By conducting this experiment, the duration of the effect of repeated stimulation was verified. The results of the verification are shown in Figure 12, plotted as a graph with the horizontal axis representing measurement timing and the vertical axis representing the 90% approximate circle area. Measurements were performed three times, and the average values ​​are shown in Figure 12.

[0106] As confirmed in Experiment 13, when a stimulation time of 1 minute was administered, the measurement results 30 minutes after the stimulation were already equivalent to those without stimulation. However, when another 1-minute stimulation was administered 30 minutes later (1 hour after the initial stimulation), the effect was observed in the measurement immediately thereafter. Furthermore, a tendency for the duration of the effect to increase was observed thereafter. This tendency was observed to become stronger with each additional 1-minute stimulation. In other words, it was confirmed that the duration of the effect was extended by administering multiple 1-minute stimulations. Thus, while the effect lasted only a short time with a single stimulation, the duration of the effect was significantly extended with multiple stimulations. Due to this carryover effect, the long-lasting effect of stimulating several times a day is highly desirable from the perspective of reducing the burden on the patient.

[0107] Various experiments were conducted to confirm the effects of the present invention, and the findings related to known technologies obtained from these experiments will now be described. It has been known that applying a sound of a specific frequency (50 to 140 Hz) at a specific volume level (70 to 85 decibels) to a subject can reduce dizziness (see Patent Document 1). However, the results of Experiments 5, 7, 8, 9, 10, etc. above confirmed that a stimulus containing a frequency component of 50 to 140 Hz can reduce dizziness even at a volume level of 70 decibels or less.

[0108] For example, in Experiment 5, applying the Brownian noise shown in Figure 8(a) to the subject reduced dizziness, but applying the Brownian noise shown in Figure 8(c) with the 400-800 Hz frequency band cut also reduced dizziness. On the other hand, applying the Brownian noise shown in Figure 8(d) with the 40-150 Hz frequency band and the 400-800 Hz frequency band cut did not reduce dizziness. From this, it can be understood that the reason the Brownian noise shown in Figure 8(c) with the 400-800 Hz frequency band cut reduced dizziness is reduced is because the noise contains a frequency band of 50-140 Hz.

[0109] When the processed Brownian noise shown in Figure 8(c) was played in the environment used in this experiment, the sound pressure level was measured for each frequency (50 to 140 Hz), and it was found to be less than 70 decibels. This means that as long as the stimulus contains frequency components between 50 and 140 Hz, it will be effective in reducing dizziness even if the sound pressure level is less than 70 decibels.

[0110] The stimulus containing a frequency component of 50 to 140 Hz does not necessarily have to be noise, but may be a pure tone having a specific frequency component in the range of 50 to 140 Hz, or a combination of multiple such pure tones. By providing the subject with a stimulus containing a frequency component in the range of 50 to 140 Hz, the subject's dizziness can be reduced even if the sound pressure level of the stimulus is 70 decibels or less.

[0111] 100, 200 Vestibular function improvement device 1 Device body 2 Headphones 3 Bone conduction earphones

Claims

1. A vestibular function improvement device comprising: a generation unit that generates an electrical signal that generates vibrations including frequency components in the range of 450 to 1500 Hz; and an output unit that outputs stimulation based on the electrical signal.

2. The vestibular function improving device according to claim 1, wherein the stimulation output by the output unit is transmitted to the vestibular system of the inner ear.

3. The vestibular function improvement device according to claim 1, wherein the stimulus is a sound stimulus.

4. The vestibular function improvement device according to claim 1, wherein the stimulation is a vibration stimulation.

5. The vestibular function improvement device according to claim 1, wherein the output section outputs the stimulus as noise containing frequency components over a predetermined range.

6. The vestibular function improvement device according to claim 5, wherein the sound pressure level of the noise in a high frequency band is lower than the sound pressure level in a frequency band ranging from 450 to 1500 Hz.

7. The vestibular function improvement device according to claim 6, wherein the high frequency band is a frequency band of 2000 Hz or higher.

8. The vestibular function improvement device according to claim 5, wherein the output unit outputs the stimulation in the form of brown noise or pink noise.

9. The vestibular function improvement device according to claim 1, wherein the stimulus is a vibration stimulus, and the output unit outputs the stimulus in the form of white noise.

10. A vestibular function improvement device according to any one of claims 1 to 9, wherein the output unit combines the stimulation with a sound different from the stimulation and outputs the combined stimulation.

11. A method for improving vestibular function, comprising: generating an electrical signal that generates vibrations having frequency components in the range of 450 to 1500 Hz; outputting a stimulus based on the electrical signal; and transmitting the stimulus to the vestibular system of the inner ear.

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