WO2019084600A1

WO2019084600A1 - A melanin production stimulating device and method of using same

Info

Publication number: WO2019084600A1
Application number: PCT/AU2018/051164
Authority: WO
Inventors: Raymond Palmer
Original assignee: Helium 3 Resources Pty Ltd
Current assignee: Helium 3 Resources Pty Ltd
Priority date: 2017-10-30
Filing date: 2018-10-30
Publication date: 2019-05-09
Anticipated expiration: 2020-04-30

Abstract

A device for stimulating the production of melanin. The device includes an electromagnetic radiation generator, an interface configured to select at least one of a visible light and infrared light, an ultrasound generator, and a second interface configured to selectively adjust a frequency of the ultrasound generator. Also provided is a method of using the device disclosed herein.

Description

A MELANIN PRODUCTION STIMULATING DEVICE

AND METHOD OF USING SAME

FIELD OF THE INVENTION

[0001 ] The present disclosure relates to a device for stimulating the production of melanin using visible light and/or infrared light or visible light and/or infrared light in combination with infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound. The present disclosure also relates to a method of using the device disclosed herein. More specifically, the present disclosure relates to a device and a method that stimulate skin tanning, preferably skin tanning in a human.

BACKGROUND OF THE INVENTION

[0002] Typically, skin tanning is achieved by exposure of skin to sunlight and/or ultraviolet light. Due to skin complexion, i.e., fair skin, not all individuals can achieve skin tanning when exposed to sunlight and/or ultraviolet light. Indeed, many individuals suffer personal discomfort and adverse effects due to exposure to the sun and/or ultraviolet light. Such personal discomfort and adverse effects include sunburn, skin damage, premature skin ageing, and skin cancer.

[0003] Alternatively, some individuals desire ongoing maintenance of their skin tan for cosmetic purposes, while avoiding the above-mentioned deleterious effects of exposure to the sun and/or ultraviolet light.

[0004] It is desirable, therefore, to find an alternative to sunlight and/or ultraviolet light to achieve a skin tan.

SUMMARY

[0005] The following is a broad summary of various exemplary embodiments of a device for stimulating the production of melanin using visible light and/or infrared light or visible light and/or infrared light in combination with infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound and a method of using the device. [0006] According to an embodiment, there is provided a melanin production stimulating device configured to stimulate melanin production, the device comprising an electromagnetic radiation generator configured to emit electromagnetic radiation; an interface configured to selectably adjust the electromagnetic radiation emitted by the electromagnetic radiation generator, when powered by a power supply, into at least one narrow wavelength range of the electromagnetic radiation selected from the group consisting of visible light and infrared light.

[0007] In another embodiment, the melanin production stimulating device may include an electromagnetic radiation generator controller in operative communication with the electromagnetic radiation generator.

[0008] In another embodiment, the melanin production stimulating device may include a wavelength adjuster to vary the wavelength of the electromagnetic radiation being emitted from the electromagnetic radiation generator, the electromagnetic radiation may be visible to infrared light having one or more wavelength being 400 nm to 1 mm.

[0009] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a wavelength of 450 nm.

[0010] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a wavelength of 565 nm.

[001 1 ] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a wavelength of 800 nm.

[0012] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a broadband wavelength of visible light.

[0013] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a combined broadband wavelength of visible light and infrared light.

[0014] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a broadband wavelength of infrared light. [0015] In another embodiment, the melanin production stimulating device may include a controller configured to adjust an intensity of the electromagnetic radiation emitted by the electromagnetic radiation generator.

[0016] In another embodiment, the melanin production stimulating device may include a timing circuit configured to shut down the electromagnetic radiation generator after a predetermined amount of elapsed time.

[0017] According to another embodiment, there is provided a melanin production stimulating device configured to stimulate melanin production, the device comprising an electromagnetic radiation generator configured to emit electromagnetic radiation; an interface configured to selectably adjust the electromagnetic radiation emitted by the electromagnetic radiation generator, when powered by a power supply, into at least one narrow wavelength range of the electromagnetic radiation selected from the group consisting of visible light and infrared light, and an infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator configured to emit infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound; and an interface configured to selectably adjust a frequency of the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound emitted by the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator, when powered by a power supply.

[0018] In another embodiment, the melanin production stimulating device may include an electromagnetic radiation generator controller in operative communication with the electromagnetic radiation generator.

[0019] In another embodiment, the melanin production stimulating device may include a wavelength adjuster to vary the wavelength of the electromagnetic radiation being emitted from the electromagnetic radiation generator.

[0020] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a wavelength of 450 nm.

[0021 ] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a wavelength of 565 nm.

[0022] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a wavelength of 800 nm. [0023] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a broadband wavelength of visible light. In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a combined broadband wavelength of visible light and infrared light.

[0024] In another embodiment, the electromagnetic radiation emitted by the electromagnetic radiation generator may have a broadband wavelength of infrared light.

[0025] In another embodiment, the melanin production stimulating device may include a controller configured to adjust an intensity of the electromagnetic radiation emitted by the electromagnetic radiation generator.

[0026] In another embodiment, the melanin production stimulating device may include a timing circuit configured to shut down the electromagnetic radiation generator after a predetermined amount of elapsed time.

[0027] In another embodiment, the melanin production stimulating device may include an infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator controller in operative communication with the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator.

[0028] In another embodiment, the melanin production stimulating device may include a frequency adjuster to adjust a frequency of the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound being emitted from the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator in a range of 0.0001 Hz - 20 Hz, 20 Hz to 20 kHz, and 20 kHz - 4 MHz, as appropriate.

[0029] In another embodiment, the melanin production stimulating device may include a timing circuit configured to shut down the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator after a predetermined amount of elapsed time.

[0030] In another embodiment, the melanin production stimulating device may include an audible sound generator controller in operative communication with the ultrasound and/or infrasound and/or electromagnetic generator. [0031 ] In another embodiment, the melanin production stimulating device may include a controller configured to adjust an intensity of the audible sound emitted by the sound generator.

[0032] In another embodiment, the melanin production stimulating device may include a timing circuit configured to shut down the audible sound generator after a predetermined amount of elapsed time.

[0033] In another embodiment, the melanin production stimulating device may include a frequency adjuster to adjust a frequency of the sound being emitted from the audible sound generator in a range of 20 Hz to 20 kHz

[0034] In another embodiment, the melanin production stimulating device may include an infrasound generator controller in operative communication with the ultrasound and/or electromagnetic generator.

[0035] In another embodiment, the melanin production stimulating device may include a controller configured to adjust an intensity of the infrasound emitted by an infrasound generator.

[0036] In another embodiment, the melanin production stimulating device may include a timing circuit configured to shut down the infrasound generator after a predetermined amount of elapsed time.

[0037] In another embodiment, the melanin production stimulating device may include a frequency adjuster to adjust a frequency of the infrasound being emitted from the infrasound generator in a range of 0.0001 Hz - 20 Hz.

[0038] In another embodiment, the melanin may be produced in a cell.

[0039] In another embodiment, the melanin may be produced in a tissue.

[0040] In another embodiment, the melanin may be produced in an organism. Preferably, the organism may be a human.

[0041 ] In another embodiment, the melanin production stimulating device may be configured to accommodate a human.

[0042] In another embodiment, the melanin production stimulating device may be a tanning bed. [0043] In another embodiment, the melanin production stimulating device may be a stand-up tanning booth.

[0044] According to an embodiment, there is provided a method of stimulating melanin production in at least part of a skin of an organism, the method comprising exposing the at least part of the skin of the organism to a narrow wavelength range of electromagnetic radiation, the electromagnetic radiation selected from the group consisting of visible light and infrared light, and simultaneously exposing the at least part of the skin of the organism to infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound having a combined frequency range of 0.0001 Hz - 20 Hz, 20 Hz to 20 kHz, and 20 kHz - 4 MHz.

[0045] Unless the meaning is clearly to the contrary, all ranges set forth herein are deemed inclusive of the endpoints.

[0046] An embodiment of the invention is now described, by way of example, with reference to the accompanying drawing. The claims as filed are incorporated by reference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 shows a schematic illustration of a melanin production stimulating device in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

[0048] The present disclosure is directed, at least in part, to a melanin production stimulating device. The present invention also encompasses a method of stimulating melanin production in at least part of a skin of an organism.

[0049] Referring to Figure 1 , reference numeral 10 generally refers to an embodiment of a melanin production stimulating device sized and configured to accommodate a human 100. The melanin production stimulating device 10 includes an electromagnetic radiation generator 12. The electromagnetic radiation generator 12 is configured to emit electromagnetic radiation 14 and is in operative communication with an interface 16. The interface 16 facilitates the selectable adjustment of the electromagnetic radiation 14 emitted by the electromagnetic radiation generator 12, when powered by a power supply 18. The interface 16 enables the electromagnetic radiation 14 to be selected into at least one narrow wavelength range of the electromagnetic radiation, i.e., from visible light and infrared light, for example 565 nm. The melanin production stimulating device 10 also includes an infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator 20 configured to emit infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound 22. An interface 24 facilitates the selectable adjustment of the frequency of the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound 22 emitted by the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator 20, when powered by the power supply 18. The melanin production stimulating device 10 also includes an electromagnetic radiation generator controller 26 in operative communication with the electromagnetic radiation generator 12. The electromagnetic radiation generator 12 includes a wavelength adjuster (not shown) to vary the wavelength of the electromagnetic radiation being emitted from the electromagnetic radiation generator. The infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator 20 is in operative communication with an infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator controller 28, which permits control of the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator 22. The melanin production stimulating device 10 has a frequency adjuster (not shown) to adjust a frequency of the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound being emitted from the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator in a range of 20 kHz - 4 MHz. The melanin stimulating device 10 has a timing circuit (not shown) for each of the electromagnetic radiation generator 12 and infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator 20. Each timing circuit (not shown) facilitates selection of a predetermined exposure time for each of the electromagnetic radiation 14 and the infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound 22.

[0050] It is to be understood that the terminology employed above is for the purpose of description and should not be regarded as limiting. The described embodiment is intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art.

[0051 ] It will be appreciated that typically, although not exclusively, electromagnetic radiation of about 400 nm to about 470 nm has depth of electromagnetic radiation penetration of <1 mm; electromagnetic radiation between about 475 nm to about 545 nm has depth of 0.3 to 0.5 mm; electromagnetic radiation of about 570 nm to about 590 nm has a depth of 0.5 mm to 2 mm; electromagnetic radiation of about 630 nm to about 790 nm has depth of 2 to 3 mm and 800 nm to about 1 .2 μιη has a depth of 5 mm to 10 mm. In general, preferred embodiments, the wavelength may be in the range 400-800nm.

[0052] It will be appreciated that typically, although not exclusively, infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound having a frequency in a range of 0.0001 Hz - 20 Hz, 20 Hz to 20 kHz, and 20 kHz - 4 MHz, as appropriate, will be emitted by the melanin production stimulating device of the invention.

[0053] The present invention contemplates stimulating melanin production in an organism, preferably a human, that uses at least one wavelength of electromagnetic radiation selected from 450 nm, 565 nm, and 800 nm in combination with ultrasound having a frequency of 1 MHz. Such a combination treatment may be useful to stimulate melanin production in all skin types, including fair skin humans.

[0054] Although different wavelengths of electromagnetic radiation are contemplated to be selected from visible light and infrared light, other parameters such as dose, fluence, power density, pulse structure and timing may be selected according to a predetermined set of criteria for specific skin types.

[0055] Preferably, the electromagnetic radiation generator is a light emitting diode, a laser, an arc lamp, an incandescent lamp, or any combination of the afore-mentioned light sources. In certain preferred embodiments, the electromagnetic radiation generator uses photons at a non-thermal irradiance to positively alter a melanin production activity in the skin, otherwise termed 'low level light therapy'. In other preferred embodiments, the electromagnetic radiation source is a coherent light source (laser) or a non-coherent light source such as a filtered lamp or a light emitting diode (LED), or a combination of a coherent light source and a non-coherent light source. In suitable embodiments, the electromagnetic radiation source is a coherent light source or a non-coherent light source, or a combination thereof. According to some embodiments, the non-coherent light source is a filtered lamp or a light emitting diode, or a combination thereof.

[0056] In preferred embodiments, the electromagnetic radiation generator includes at least one light emitting diode (LED), as is known in the art. The LED device may be configured to emit one or a plurality of wavelengths or spectral ranges. By way of example, an LED device may be a red LED that emits only in the red spectral range. Alternatively, the LED device may be configured to emit electromagnetic radiation in the red spectral range and the near infra-red spectral range. In some preferred embodiments, the LED is an organic LED (OLED). An OLED, as would be known by a skilled addressee, emits light due to electroluminescence of thin films of organic semiconductors. An OLED is a light emitting organic material that is suitable for use in an OLED. Preferably, the light emitting organic material is selected from a small molecule, a polymer, a dendrimer and any combinations thereof. It will be appreciated that an OLED may have a plurality of layers of a light emitting organic material. In an OLED, the organic semiconductors may be deposited on a glass substrate or on substrate constructed from a flexible plastic such as, but not limited to, polyethylene terephthalate. A flexible OLED offers particular advantages of being bendable and lightweight. The invention also contemplates use of an inorganic LED. Preferably, the inorganic LED is a flexible LED. Other embodiments relating to an LED contemplate a quantum dot LED.

[0057] Delivery of the electromagnetic radiation and in particular delivery of light by an LED device may be either continuous or in a pulsed mode with specific pulse sequences and durations. The choice of either continuous mode or pulsed mode is dependent on the application as is known by a skilled addressee. It is also contemplated that certain embodiments employ a combination of a continuous mode and a pulsed mode.

[0058] The present disclosure contemplates embodiments that include an ultrasound frequency adjuster to adjust a frequency of the ultrasound emitted from the ultrasound generator. Preferably, the ultrasound is selected from the range 20 kHz - 4 MHz. [0059] Any suitable power source may be included in the melanin production stimulating device of the present disclosure. The power source may be a full battery unit integral with the melanin production stimulating device. Alternatively, the power source may be configured to be rechargeable, for example by inclusion of an AC power socket or a USB socket. It will be appreciated that the power source may be configured to suit a particular electromagnetic radiation generator, as will be known by a person of skill in the art.

[0060] Preferred embodiments relating to the melanin production stimulating device of the present disclosure include a timing circuit configured to stop the generation of electromagnetic radiation and/or ultrasound after a predetermined amount of elapsed time. Such a timing circuit is particularly advantageous for a pulsed mode of operation. For example, a predetermined amount of elapsed period of time may be about 10 seconds, about 20 seconds, about 30 seconds, about 40 seconds, about 50 seconds, and about 60 seconds or more, 1 hour or 2 hours. The predetermined amount of elapsed time is dependent on the application/treatment envisaged and the skin type of the user. A melanin production stimulating treatment regime may include a single exposure, alternatively a treatment course of over a number of hours, days or weeks, as is required.

[0061 ] The present disclosure contemplates a method of stimulating melanin production in at least part of a skin of an organism, the method includes exposing the at least part of the skin of the organism to a narrow wavelength range of electromagnetic radiation, the electromagnetic radiation selected visible light and infrared light, and simultaneously exposing the at least part of the skin of the organism to infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound having a frequency in a range of 0.0001 Hz - 20 Hz, 20 Hz to 20k Hz, and 20 kHz - 4 MHz, as appropriate.

[0062] Ranges are to be interpreted as being fully inclusive of all values between the limits.

[0063] The following prophetic examples are made: Example 1

The melanin stimulating device described herein is dimensioned and configured as a tanning bed. The user, a human, can be accommodated in either a prone or a supine position within the tanning bed while being exposed to the relevant electromagnetic radiation to stimulate melanin production in the skin of the human. The electromagnetic radiation may be one or more wavelength between 400 nm and 1 mm.

Example 2

The melanin stimulating device described herein is dimensioned and configured as a tanning booth. The user, a human, can be accommodated in an upright position within the tanning bed while being exposed to the relevant electromagnetic radiation to stimulate melanin production in the skin of the human. The electromagnetic radiation may be one or more wavelength between 400 nm and 1 mm.

Example 3

The melanin stimulating device described herein is a wearable garment. The garment is typically a flexible garment that forms a comfortable fit over at least a part of a user's body. The garment having an operative inner side and outer side. The electromagnetic radiation generator is configured to emit electromagnetic radiation inward relative to the operative inner side of the garment. The electromagnetic radiation generator is an OLED, the organic semiconductors is deposited on a substrate constructed from a flexible plastic such as, but not limited to, polyethylene terephthalate. A flexible OLED offers particular advantages of being bendable and lightweight, which is suitable for the wearable garment. The electromagnetic radiation may be 450 nm, 565 nm, and/or 800 nm.

Example 4

The melanin stimulating device described herein is dimensioned and configured as a tanning bed. The user, a human, can be accommodated in either a prone or a supine position within the tanning bed while being exposed to the relevant electromagnetic radiation and infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound to stimulate melanin production in the skin of the human. The electromagnetic radiation may be 450 nm, 565 nm, and/or 800 nm in combination with ultrasound having a frequency of 500 kHz. Example 5

The melanin stimulating device described herein is dimensioned and configured as a tanning booth. The user, a human, can be accommodated in an upright position within the tanning bed while being exposed to the relevant electromagnetic radiation and infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound to stimulate melanin production in the skin of the human. The electromagnetic radiation may be 450 nm, 565 nm, and/or 800 nm in combination with ultrasound having a frequency of 1 MHz.

Example 6

The melanin stimulating device described herein is a wearable garment. The garment is typically a flexible garment that forms a comfortable fit over at least a part of a user's body. The garment having an operative inner side and outer side. The electromagnetic radiation generator and infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound generator are configured to emit electromagnetic radiation and infrasound, sound, ultrasound, or any combination of infrasound, sound, and/or ultrasound, respectively, inward relative to the operative inner side of the garment. The electromagnetic radiation generator is an OLED, the organic semiconductors is deposited on a substrate constructed from a flexible plastic such as, but not limited to, polyethylene terephthalate. A flexible OLED offers particular advantages of being bendable and lightweight, which is suitable for the wearable garment. The electromagnetic radiation may be 450 nm, 565 nm, and/or 800 nm in combination with ultrasound having a frequency of 1 .5 MHz.

[0064] It is to be understood that the terminology employed above is for the purpose of description and should not be regarded as limiting. The described embodiments are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art.

Claims

1 . A melanin production stimulating device configured to stimulate melanin production, the device comprising:

(a) an electromagnetic radiation generator configured to emit electromagnetic radiation;

(b) an interface configured to selectably adjust the electromagnetic radiation emitted by the electromagnetic radiation generator, when powered by a power supply, into at least one narrow wavelength range of the electromagnetic radiation selected from the group consisting of:

(i) visible light; and

(ii) infrared light;

(c) an ultrasound generator configured to emit ultrasound; and

(d) an interface configured to selectably adjust a frequency of the ultrasound emitted by the ultrasound generator, when powered by a power supply.

2. The melanin production stimulating device of claim 1 , including an electromagnetic radiation generator controller in operative communication with the electromagnetic radiation generator.

3. The melanin production stimulating device of claim 1 , including a wavelength adjuster to vary the wavelength of the electromagnetic radiation being emitted from the electromagnetic radiation generator.

4. The melanin production stimulating device of claim 3, wherein the electromagnetic radiation emitted by the electromagnetic radiation generator has a wavelength of 450 nm.

5. The melanin production stimulating device of claim 3, wherein the electromagnetic radiation emitted by the electromagnetic radiation generator has a wavelength of 565 nm.

6. The melanin production stimulating device of claim 3, wherein the electromagnetic radiation emitted by the electromagnetic radiation generator has a wavelength of 800 nm.

7. The melanin production stimulating device of claim 1 , including a control configured to adjust an intensity of the electromagnetic radiation emitted by the electromagnetic radiation generator.

8. The melanin production stimulating device of claim 1 , including a timing circuit configured to shut down the electromagnetic radiation generator after a predetermined amount of elapsed time.

9. The melanin production stimulating device of claim 1 , including an ultrasound generator controller in operative communication with the ultrasound generator.

10. The melanin production stimulating device of claim 1 , including a frequency adjuster to adjust a frequency of the ultrasound being emitted from the ultrasound generator in a range of 20 kHz - 4 MHz.

1 1 . The melanin production stimulating device of claim 1 , including a timing circuit configured to shut down the ultrasound generator after a predetermined amount of elapsed time.

12. The melanin production stimulating device of claim 1 , wherein the melanin is produced in a cell.

13. The melanin production stimulating device of claim 1 , wherein the melanin is produced in a tissue.

14. The melanin production stimulating device of claim 1 , wherein the melanin is produced in an organism.

15. The melanin production stimulating device of claim 1 1 , wherein the organism is a human.

16. The melanin production stimulating device of claim 1 , wherein the melanin production stimulating device is configured to accommodate a human.

17. The melanin production stimulating device of claim 1 , wherein the melanin production stimulating device is a tanning bed.

18. The melanin production stimulating device of claim 1 , wherein the melanin production stimulating device is a stand-up tanning booth.

19. A method of stimulating melanin production in at least part of a skin of an organism, the method comprising:

(a) exposing the at least part of the skin of the organism to a narrow wavelength range of electromagnetic radiation, the electromagnetic radiation selected from the group consisting of:

(i) visible light; and

(ii) infrared light; and

(b) simultaneously exposing the at least part of the skin of the organism to ultrasound having a frequency in a range of 20 kHz - 4 MHz.