A method for exploring sounds that relieve stress.

Abstract

Efficiently explore sounds that help alleviate stress. [Solution] A search method for searching for sounds to alleviate stress in animals, The first application step S4 involves applying a test sound to an experimental animal, A first measurement step S5 involves measuring the stress on the experimental animal to which the test sound has been applied, Based on the measurement results of the first measurement step S5, a first selection step S6 is performed to select a test sound that has a stress-relieving effect on the experimental animal, Setting step S7, which sets candidate sounds that are candidates for the sound based on the test sound selected in the first selection step, A search method that has [something].

Description

Technical Field

[0001] The present invention relates to a method for exploring sounds for stress relief.

Background Art

[0002] In modern society, stress is a major issue, but relieving stress through medication has a high hurdle and there are concerns about side effects. On the other hand, music therapy is a method of promoting physical and mental health using music and has been used in many cultures and medical settings from ancient times to the present.

[0003] On the other hand, since the relaxation effect of music depends on individual experience and knowledge, it is necessary to find universal effectiveness. Non-Patent Document 1 discloses exploring sounds that give pleasure or discomfort by giving various consonant and dissonant stimuli to more than 250 subjects and having them evaluate.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method disclosed in Non-Patent Document 1, since the subjects have to evaluate a large number of sounds, there is a problem that the burden on the subjects is large and it takes time to explore sounds.

[0006] This invention has been made in view of the above problems, and aims to efficiently search for sounds that alleviate stress. [Means for solving the problem]

[0007] To solve the above problems, the present invention includes the following embodiments. Section 1. A search method for exploring sounds that alleviate stress in animals, The first step involves applying a test sound to an experimental animal, A first measurement step involves measuring the stress on the experimental animal to which the test sound has been applied, A first selection step involves selecting a test sound that has a stress-reducing effect on the experimental animal based on the measurement results of the first measurement step, A setting step in which candidate sounds are selected based on the test sound selected in the first selection step, A search method that has [something]. Section 2. A second dispensing step involves dispensing the aforementioned animal to the subject, A second measurement step involves measuring the stress of the animal before and after the application of the candidate sound, A second selection step in which the sound is selected based on the measurement results of the second measurement step, The search method described in item 1, further comprising the above. Section 3. The search method according to item 1 or 2, wherein the test sound and the candidate sound are compound sounds. Section 4. The search method according to item 3, wherein the aforementioned compound sound is a compound sound consisting of two sounds with different frequencies. Section 5. The search method according to item 3 or 4, wherein the setting step involves setting the candidate sounds by changing the frequencies of each sound constituting the test sound to frequencies within the audible range of the animal such that the ratio of the frequencies of each sound is the same. Section 6. The aforementioned experimental animal is a rodent, and the search method is as described in any of sections 1 to 5. Section 7. The search method according to item 6, wherein the rodent is a mouse.

Advantages of the Invention

[0008] According to the present invention, it is possible to efficiently search for sounds for relieving stress.

Brief Description of the Drawings

[0009] [Figure 1] It is a flowchart showing the first half of the processing procedure of the search method according to an embodiment of the present invention. [Figure 2] It is a flowchart showing the second half of the processing procedure of the search method according to an embodiment of the present invention. [Figure 3] It is a schematic diagram for explaining the breeding state of mice. <000D074>[[ID=D4]] [Figure 4] It is a diagram showing a schedule for presenting a test sound to a mouse and the like. [Figure 5] It is a waveform diagram showing the waveform of the test sound. [Figure 6] It is a graph showing the cortisol concentrations of group-housed mice and individually-housed mice. [Figure 7] It is a diagram showing the timing of presenting pure tones and complex tones to the subject. [Figure 8] It is a schematic diagram showing the positions of the electrodes of the electroencephalograph worn on the head of the subject. [Figure 9] It is a graph showing the average value of the α-wave intensity in the frontal lobe of the subject when a pure tone is presented and when a second test sound is presented. [Figure 10] It is a graph showing the correlation between the stress-relieving effect of complex sounds on mice and the stress-relieving effect on humans with respect to the frequency ratio of the complex sounds.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiments, and various modifications are possible without departing from the gist thereof.

[0011] Figures 1 and 2 are flowcharts showing the processing procedures of a search method according to an embodiment of the present invention. The search method is a method for searching for sounds for relieving stress in animals. In this embodiment, the animal is a human, but may be an animal other than a human such as a pet or livestock. In order to avoid confusion with the experimental animals described later, hereinafter, the "animal" is referred to as the "target animal". Also, in order to avoid confusion with the test sounds and candidate sounds described later, hereinafter, the "sound for relieving stress in animals" is referred to as the "relieving sound".

[0012] This search method has steps S1 to S12. Generally speaking, steps S1 to S7 are the first half, and steps S8 to S12 are the second half. In steps S1 to S7 shown in Figure 2, candidate sounds that are candidates for the relieving sound are set by applying test sounds to the experimental animals.

[0013] In step S1, experimental animals are prepared. The experimental animals are not particularly limited as long as they are animals having hearing other than humans. However, from the ease of the experiment, rodent animals such as mice and rats are preferable, and mice are particularly preferable.

[0014] In step S2, test sounds are created. In this embodiment, the test sound is a composite sound composed of two sounds, but may be a composite sound composed of three or more sounds. The type of the test sound may be only one type, but it is preferable to set a plurality of types of test sounds in which the ratio of the frequencies of each sound constituting the test sound (hereinafter referred to as the "frequency ratio") is different. In this embodiment, n (n is an integer of 2 or more) test sounds with different frequency ratios are set.

[0015] Note that the order of steps S1 and S2 is not limited.

[0016] In step S3, stress is imposed on the experimental animals. The method of imposing stress is not particularly limited. However, when the experimental animal is a mouse, stress is imposed by individually raising the group-housed mice.

[0017] In step S4 (first application step), the experimental animals are given test sounds. In this embodiment, the experimental animals are divided into n+1 groups, the experimental animals in group n are given test sounds, and the experimental animals in group 1 are not given test sounds. That is, the experimental animals in groups 1 to n are given the first to n test sounds, respectively, and the experimental animals in the remaining group (n+1) are not given test sounds.

[0018] In step S5 (first measurement step), the stress of experimental animals that were exposed to the test sound (experimental animals from group 1 to group n) and the stress of experimental animals that were not exposed to the test sound (experimental animals from group n+1) are measured. The method of measuring stress is not particularly limited, but if the experimental animals are mice, stress can be measured based on serum cortisol concentration or corticosterone concentration, and from the viewpoint of the persistence of the response, cortisol concentration is preferred as the indicator.

[0019] In step S6 (first selection step), a test sound that has a stress-reducing effect on the experimental animals is selected based on the measurement results in step S5. In this embodiment, the average stress level of the experimental animals is calculated for each group, and the test sound applied to the group of experimental animals that shows a larger decrease in the average stress level compared to the (n+1)th group of experimental animals that were not given a test sound is selected as a test sound that has a stress-reducing effect. The threshold for the decrease in the average stress level can be set appropriately depending on the number of test sounds to be selected, etc.

[0020] In step S5, it is not necessary to include a group of experimental animals that are not subjected to test sounds (group n+1). In this case, in step S6, the test sounds applied to the experimental animals in the group with relatively low average stress levels are selected as test sounds that have a stress-relieving effect.

[0021] In step S7 (setting step), candidate sounds for the relaxation sound are set based on the test sound selected in step S6. If the frequency range of the test sound is within the audible range of the target animal, the test sound selected in step S6 becomes the candidate sound as is. On the other hand, if the frequency range of the test sound is outside the audible range of the target animal, candidate sounds are set by changing the frequencies of each sound that make up the test sound to frequencies within the audible range of the target animal so that the ratio of the frequencies of each sound is the same. For example, if the target animal is a human and the frequency of the test sound is around 8000Hz, which is within the audible range of a mouse, candidate sounds are set by lowering the frequency of the test sound to around 1000Hz, which is within the audible range of a human.

[0022] Based on the above, candidate sounds that can be used as relaxation sounds are set. Next, in steps S8 to S12 shown in Figure 2, a relaxation sound is selected from the candidate sounds by applying the set candidate sounds to the target animal. In this embodiment, the target animal is a human.

[0023] In step S8, stress is applied to the target animal. The method of applying stress is not particularly limited, but in this embodiment, stress is applied by applying a pure tone to the target animal for 2 minutes.

[0024] In step S9 (second assignment step), candidate sounds are assigned to the target animal. In this embodiment, one candidate sound is assigned to the target animal for 2 minutes.

[0025] In step S10 (second measurement step), the stress of the target animal is measured before and after the application of the candidate sound. The method for measuring stress is not particularly limited, but in this embodiment, the brainwaves of the target animal are measured, and the stress is determined from the intensity of the alpha wave component of the brainwaves.

[0026] If there are multiple candidate sounds (YES in step S11), repeat steps S8-S10 for the other candidate sounds. After performing steps S8-S10 for all candidate sounds (NO in step S11), proceed to step S12.

[0027] In step S12 (second selection step), a relaxation sound is selected based on the measurement results from step S9. In this embodiment, the difference in stress (reduction) before and after the application of each candidate sound is calculated, and the candidate sound with the largest reduction is selected as the relaxation sound.

[0028] As described above, it is possible to search for sounds that can alleviate stress in the target animal. In this embodiment, candidate sounds that can be used as stress-relieving sounds are set in advance in steps S1 to S7 by conducting experiments using experimental animals. This makes it possible to reduce the number of candidate sounds to be applied to the target animal to less than the number of test sounds, thereby reducing the burden on the target animal.

[0029] Furthermore, as shown in the examples described later, there is a high correlation between the stress-relieving effect of the frequency ratio of the composite sound on experimental animals and the stress-relieving effect on the target animal. Therefore, candidate sounds with the same frequency ratio as test sounds that have shown a stress-relieving effect on experimental animals are highly likely to also have a stress-relieving effect on the target animal, allowing for efficient search for stress-relieving sounds.

[0030] (Additional notes) Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0031] For example, steps S8 to S12 shown in Figure 2 may be omitted, and the candidate sound set in step S7 may be used directly as the relaxation sound. This makes the search for relaxation sounds more efficient. [Examples]

[0032] The following describes embodiments of the present invention. In this embodiment, it was demonstrated that there is a high correlation between the stress-reducing effect of the frequency ratio of the complex sound on experimental animals and the stress-reducing effect on the target animals.

[0033] (Evaluation of stress reduction effects in laboratory animals) First, the relationship between the frequency ratio of test sounds and the stress-reducing effect on experimental animals was evaluated by applying test sounds to the experimental animals. In this example, the experimental animals were mice (C57BL / 6J). The mice were kept in a living environment with a temperature of 23±2℃ and a humidity of 50±10%, and the light cycle was set to 8am-8pm as daytime. The mice were acclimatized for at least one week, and then bred and raised at the applicant's facility. Growth was carried out in a group housing environment. Male mice aged 9-11 weeks were used in the experiment.

[0034] Subsequently, the mice were subjected to stress by being housed in isolation. Since mice normally live in groups, it is known that separating them from their group causes anxiety symptoms and leads to a stressed state (Hilakivi, LA, Ota, M., & Lister, R. (1989). Effect of isolation on brain monoamines and the behavior of mice in tests of exploration, locomotion, anxiety and behavioral 'despair.' Pharmacology Biochemistry and Behavior, 33(2), 371-374. https: / / doi.org / 10.1016 / 0091-3057(89)90516-9).

[0035] In this example, as shown in Figure 3(a), some mice raised in a group rearing environment were moved to individual rearing conditions as shown in Figure 3(b), and simultaneously reared in a soundproof chamber (sound attenuating chamber model MC-035, manufactured by Muromachi Machinery Co., Ltd.) capable of presenting sounds. Specifically, as shown in Figure 4, the mice were reared individually for the first three days to induce stress, becoming stressed mice. Furthermore, some of the stressed mice were presented with the test sound described below for four days, from the fourth to the seventh day. The presentation time was six hours, from 9 PM to 3 AM the following morning. The other stressed mice were not presented with the test sound.

[0036] For the test sound presentation, a speaker (BS-301B manufactured by TOA Corporation) was placed inside a soundproof box, and the presentation sound and presentation time were set using a script created in MATLAB (MathWord, USA). An audio interface (UAC-8 manufactured by Zoom Corporation) and an amplifier (P-60F manufactured by TOA Corporation) were used to present a 60dB sound.

[0037] The test sounds were four types of composite sounds with a fundamental frequency of 8000Hz and frequency ratios that were simple integer ratios. A composite sound of 8000Hz and 12000Hz was used when the frequency ratio was 2:3 (Figure 5(a)), a composite sound of 8000Hz and 10000Hz was used when the frequency ratio was 4:5 (Figure 5(b)), a composite sound of 8000Hz and 8533Hz was used when the frequency ratio was 15:16 (Figure 5(c)), and a composite sound of 8000Hz and 11500Hz was used when the frequency ratio was 32:46 (Figure 5(d)). Each stressed mouse was presented with one type of composite sound for four days. At 10:00 a.m. on the eighth day after presentation of the test sounds, the stress of the stressed mice was measured, and the stress reduction effect of each type of composite sound presented was evaluated for the stressed mouse group.

[0038] Stress in mice was measured based on blood cortisol concentration. Specifically, mice were anesthetized with isoflurane and blood was collected directly from the heart. After blood collection, serum was collected by centrifugation and stored at -80°C. Then, cortisol was detected from the serum using the ELISA method with an assay kit (DetectX Cortisol ELISA Kit, Arbor Assays). For quantification, a calibration curve was established using standard substances according to the manufacturer's manual, and the cortisol concentration of the serum sample was measured. Since the cortisol concentration increases with increasing stress, stress can be measured based on cortisol concentration. Stress was also measured using the same method for mice that were not subjected to stress (mice housed in groups rather than individually).

[0039] Figure 6 is a graph showing the cortisol concentrations of mice housed in groups and mice housed individually (stress-loaded mice). Tables 1 and 2 show the data on cortisol changes induced by the presentation of test sounds and multiple testing, respectively.

[0040] [Table 1]

[0041] [Table 2]

[0042] From the results above, it was revealed that the cortisol-reducing effect, i.e., the stress-relieving effect in mice, was particularly strong with complex sounds with a frequency ratio of 4:5 and 15:16, with the complex sound with a frequency ratio of 4:5 showing the greatest effect.

[0043] (Evaluation of stress reduction effect on target animals) To investigate whether evaluation results from experimental animals can be extrapolated to target animals, the relationship between the frequency ratio of the second test sound and the stress reduction effect in the target animals was evaluated by administering a sound with the same frequency ratio as the test sound (hereinafter referred to as the "second test sound") to the target animals. In this example, the target animals were humans, specifically 33 subjects aged 19 to 55 years (average age 29.8 years, standard deviation 11.7, 11 males, 22 females).

[0044] The subjects' stress levels were determined by measuring electroencephalograms (EEGs) and assessing changes in alpha waves, which indicate relaxation (anti-stress) effects. First, subjects were fitted with EEG devices in a magnetically shielded room. Pure tones and secondary test tones were presented alternately, with the frequency ratio of the secondary test tones varying, and the fluctuations in alpha waves were measured during this time. Specifically, as shown in Figure 7, a pure tone was presented at 60 dB for 2 minutes (stress phase), followed by a secondary test tone (sound A) consisting of two sounds for 2 minutes (stress recovery phase). The stress phase and stress recovery phase were then repeated alternately. The frequency ratios of the secondary test tones were 2:3, 15:16, 4:5, and 32:45, and the presentation order of these four types of secondary test tones was randomly set for each subject. The frequency of the pure tone was 1 kHz, and the secondary test tone was a composite sound consisting of two sounds, with the lower frequency of the two sounds being 1 kHz. To maintain a consistent level of attention to sound, participants watched silent videos during the experiment.

[0045] The pure tone and the second test tone were presented via headphones (Sennheiser HD800) through an audio interface (RME Fireface UFX) and a headphone amplifier (Sennheiser HDVD800) from a personal computer.

[0046] A biosignal recording device (Polymate Pro MP6100, manufactured by Miyuki Giken Co., Ltd.) was used to measure electroencephalograms (EEGs). The sampling frequency was 400 Hz. As shown in Figure 8, active electrodes were placed in accordance with the international 10-20 system at Fz (frontal pole), F7, F8 (frontal), T3, T4 (temporal), T5, T6 (temporal), Cz (parietal), and Pz (occipital), while reference electrodes were placed on the earlobes of both ears (A1, A2). The recorded EEGs were passed through a band-pass filter (alpha wave band: 8-13 Hz), and the mean squared values ​​for each sound listening period were calculated. Furthermore, the ratio of the mean squared values ​​of alpha waves during the stress period and the stress recovery period was calculated.

[0047] Statistical analysis was performed using statistical software (Jamovi) (R Core Team, 2021; The Jamovi Project, 2023).

[0048] Figure 9 is a graph showing the average alpha wave intensity in the frontal lobe (electrode position Fz) of subjects when a pure tone was presented (non) and when the second test tone was presented. Table 3 shows detailed numerical values ​​for alpha wave intensity, etc.

[0049] [Table 3]

[0050] From the results above, it was confirmed that the alpha wave enhancement effect, i.e., the stress reduction effect in humans, was particularly strong for complex sounds with a frequency ratio of 4:5 and 15:16, similar to the experiments with mice, with the complex sound with a frequency ratio of 4:5 showing the greatest effect.

[0051] Figure 10 is a graph showing the correlation between the stress-reducing effect of complex sound frequency ratios in mice and the stress-reducing effect in humans. The horizontal axis represents the blood cortisol concentration in mice, and the vertical axis represents the alpha wave intensity in humans. When the correlation between the blood cortisol concentration in mice upon presentation (or non-presentation) of a test sound and the alpha wave intensity in humans upon presentation of a second test sound (or pure tone) was plotted and fitted with a linear function, the correlation coefficient R² = 0.9657 was obtained. This demonstrates a high correlation between the stress-reducing effect of complex sound frequency ratios in experimental animals and the stress-reducing effect in the target animal. Therefore, it is considered that the properties of test sounds that showed a stress-reducing effect in experimental animals are highly generalizable to the target animal. [Industrial applicability]

[0052] This invention can be applied not only to the search for sounds that alleviate human stress, but also to the search for sounds that alleviate stress in non-human animals such as pets and livestock.

Claims

1. A search method for exploring sounds that alleviate stress in animals, The first step involves applying a test sound to an experimental animal, A first measurement step involves measuring the stress on the experimental animal to which the aforementioned test sound has been applied, A first selection step involves selecting a test sound that has a stress-reducing effect on the experimental animal based on the measurement results of the first measurement step, A setting step in which candidate sounds are selected based on the test sound selected in the first selection step, A search method that has [something].

2. A second application step in which the candidate sound is applied to the animal, A second measurement step involves measuring the stress of the animal before and after the application of the candidate sound, A second selection step in which the sound is selected based on the measurement results of the second measurement step, The search method according to claim 1, further comprising the above.

3. The search method according to claim 1 or 2, wherein the test sound and the candidate sound are compound sounds.

4. The search method according to claim 3, wherein the composite sound is a composite sound consisting of two sounds with different frequencies.

5. The search method according to claim 3, wherein in the setting step, candidate sounds are set by changing the frequencies of each sound constituting the test sound to frequencies within the audible range of the animal such that the ratio of the frequencies of each sound is the same.

6. The search method according to claim 1 or 2, wherein the experimental animal is a rodent.

7. The search method according to claim 6, wherein the rodent is a mouse.

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