IL294440B

IL294440B - Hookah device

Info

Publication number: IL294440B
Application number: IL294440A
Authority: IL
Inventors: Imad Lahoud; Saleh Ghannam Almazrouei Mohammed Alshaiba; Sajid Bhatti; Jeff Machovec; Clement Lamoureux
Original assignee: Shaheen Innovations Holding Ltd; Imad Lahoud; Saleh Ghannam Almazrouei Mohammed Alshaiba; Sajid Bhatti; Jeff Machovec; Clement Lamoureux
Priority date: 2020-04-06
Filing date: 2021-04-06
Publication date: 2022-12-01
Also published as: GB202104872D0; CA3161558C; CA3161558A1; JP7397202B2; GB202111261D0; JP2023500985A; GB202113623D0; WO2021205158A1; AU2021252182A1; CL2022001809A1; GB2597613A; GB2597610A; JP2023502155A; GB2592144A; IL294440B2; KR102576418B1; CL2022001808A1; JOP20220149A1; GB2592144B; IL294440A

Description

HOOKAH DEVICE Cross references to related applications The present application claims the benefit of priority to and incorporates by reference herein the entirety of each of: European patent application no. 20168245.7, filed on 6 April 2020; European patent application no. 20168231.7, filed on 6 April 2020; European patent application no. 20168938.7, filed on 9 April 2020; United States patent application no. 16/889667, filed on 1 June 2020; United States patent application no. 17/065992, filed on 8 October 2020; United States patent application no. 17/122025, filed on 15 December 2020; and United States patent application no. 17/220189, filed on 1 April 2021.

Field The present invention relates to a hookah device. The present invention more particularly relates to a hookah device which generates a mist using ultrasonic vibrations.

Background The traditional hookah is a smoking device which burns tobacco leaves that have been crushed and prepared specifically to be heated using charcoal. The heat from the charcoal causes the crushed tobacco leaves to burn, producing smoke that is pulled through water in a glass chamber and to the user by inhalation. The water is used to cool the hot smoke for ease of inhalation.

Hookah use began centuries ago in ancient Persia and India. Today, hookah cafés are gaining popularity around the world, including the United Kingdom, France, Russia, the Middle East and the United States.

A typical modern hookah has a head (with holes in the bottom), a metal body, a water bowl and a flexible hose with a mouthpiece. New forms of electronic hookah products, including steam stones and hookah pens, have been introduced. These products are battery or mains powered and heat liquid 1 containing nicotine, flavorings and other chemicals to produce smoke which is inhaled.

Although many users consider it less harmful than smoking cigarettes, hookah smoking has many of the same health risks as cigarette smoking.

Thus, a need exists in the art for an improved hookah device which seeks to address at least some of the problems described herein.

The present invention seeks to provide an improved hookah device.

Summary According to some arrangements, there is provided a hookah device comprising: a plurality of ultrasonic mist generator devices which are each provided with a respective mist outlet port; a driver device which is connected electrically to each of the mist generator devices and configured to activate the mist generator devices; and a hookah attachment arrangement which is configured to attach the hookah device to a hookah, the hookah attachment arrangement having a hookah outlet port which provides a fluid flow path from the mist outlet ports of the mist generator devices and out of the hookah device such that, when at least one of the mist generator devices is activated by the driver device, mist generated by each activated mist generator device flows along the fluid flow path and out of the hookah device to the hookah.

In some arrangements, the driver device is connected electrically to each of the mist generator devices by a data bus and the driver device is configured to identify and control each mist generator device using a respective unique identifier for the mist generator device.

In some arrangements, each mist generator device comprises: an identification arrangement comprising: an integrated circuit having a memory which stores a unique identifier for the mist generator device; and an electrical connection 2 which provides an electronic interface for communication with the integrated circuit.

In some arrangements, the driver device is configured to control each respective mist generator device to activate independently of the other mist generator devices.

In some arrangements, the driver device is configured to control the mist generator devices to activate in a predetermined sequence.

In some arrangements, each mist generator device comprises: a manifold having a manifold pipe which is in fluid communication with the mist outlet ports of the mist generator devices, wherein mist output from the mist outlet ports combines in the manifold pipe and flows through the manifold pipe and out from the hookah device.

In some arrangements, the hookah device comprises four mist generator devices which are releasably coupled to the manifold at 90º relative to one another.

In some arrangements, each mist generator device is releasably attached to the driver device so that each mist generator device is separable from the driver device.

In some arrangements, each mist generator device comprises: a mist generator housing which is elongate and comprises an air inlet port and the said mist outlet port; a liquid chamber provided within the mist generator housing, the liquid chamber containing a liquid to be atomized; a sonication chamber provided within the mist generator housing; a capillary element extending between the liquid chamber and the sonication chamber such that a first portion of the capillary element is within the liquid chamber and a second portion of the capillary element is within the sonication chamber; an ultrasonic transducer 3 having a generally planar atomization surface which is provided within the sonication chamber, the ultrasonic transducer being mounted within the mist generator housing such that the plane of the atomization surface is substantially parallel with a longitudinal length of the mist generator housing, wherein part of the second portion of the capillary element is superimposed on part of the atomization surface, and wherein the ultrasonic transducer is configured to vibrate the atomization surface to atomize a liquid carried by the second portion of the capillary element to generate a mist comprising the atomized liquid and air within the sonication chamber; and an airflow arrangement which provides an air flow path between the air inlet port, the sonication chamber and the air outlet port.

In some arrangements, each mist generator device further comprises: a transducer holder which is held within the mist generator housing, wherein the transducer element holds the ultrasonic transducer and retains the second portion of the capillary element superimposed on part of the atomization surface; and a divider portion which provides a barrier between the liquid chamber and the sonication chamber, wherein the divider portion comprises a capillary aperture through which part of the first portion of the capillary element extends.

In some arrangements, the capillary element is 100% bamboo fiber.

In some arrangements, the airflow arrangement is configured to change the direction of a flow of air along the air flow path such that the flow of air is substantially perpendicular to the atomization surface of the ultrasonic transducer as the flow of air passes into the sonication chamber.

In some arrangements, the liquid chamber contains a liquid having a kinematic viscosity between 1.05 Pa•s and 1.412 Pa•s and a liquid density between 1.1 g/ml and 1.3 g/ml. 4 In some arrangements, the liquid chamber contains a liquid comprising approximately a 2:1 molar ratio of levulinic acid to nicotine.

In some arrangements, the driver device comprises: an AC driver which is configured to generate an AC drive signal at a predetermined frequency to drive a respective ultrasonic transducer in each mist generator device; an active power monitoring arrangement which is configured to monitor the active power used by the ultrasonic transducer when the ultrasonic transducer is driven by the AC drive signal, wherein the active power monitoring arrangement is configured to provide a monitoring signal which is indicative of an active power used by the ultrasonic transducer; a processor which is configured to control the AC driver and to receive the monitoring signal drive from the active power monitoring arrangement; and a memory storing instructions which, when executed by the processor, cause the processor to: A. control the AC driver to output an AC drive signal to the ultrasonic transducer at a predetermined sweep frequency; B. calculate the active power being used by the ultrasonic transducer based on the monitoring signal; C. control the AC driver to modulate the AC drive signal to maximize the active power being used by the ultrasonic transducer; D. store a record in the memory of the maximum active power used by the ultrasonic transducer and the sweep frequency of the AC drive signal; E. repeat steps A-D for a predetermined number of iterations with the sweep frequency incrementing with each iteration such that, after the predetermined number of iterations has occurred, the sweep frequency has been incremented from a start sweep frequency to an end sweep frequency; F. identify from the records stored in the memory the optimum frequency for the AC drive signal which is the sweep frequency of the AC drive signal at which a maximum active power is used by the ultrasonic transducer; and G. control the AC driver to output an AC drive signal to the ultrasonic transducer at the optimum frequency to drive the ultrasonic transducer to atomize a liquid.

In some arrangements, the active power monitoring arrangement comprises: a current sensing arrangement which is configured to sense a drive current of the AC drive signal driving the ultrasonic transducer, wherein the active power monitoring arrangement is configured to provide a monitoring signal which is indicative of the sensed drive current.

In some arrangements, the memory stores instructions which, when executed by the processor, cause the processor to: repeat steps A-D with the sweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 2960kHz.

In some arrangements, the memory stores instructions which, when executed by the processor, cause the processor to: repeat steps A-D with the sweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 3100kHz.

In some arrangements, the AC driver is configured to modulate the AC drive signal by pulse width modulation to maximize the active power being used by the ultrasonic transducer.

According to some arrangements, there is provided a hookah comprising: a water chamber; an elongate stem having a first end which is attached to the water chamber, the stem comprising a mist flow path which extends from a second end of the stem, through the stem, to the first end; and a hookah device according to any one of claims 1 to 19 as defined hereinafter, wherein the hookah attachment arrangement of the hookah device is attached to the stem of the hookah at the second end of the stem. 6 Brief description of the drawings So that the present invention may be more readily understood, embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded view of components of an ultrasonic mist inhaler.

Figure 2 is an exploded view of components of an inhaler liquid reservoir structure.

Figure 3 is a cross section view of components of an inhaler liquid reservoir structure.

Figure 4A is an isometric view of an airflow member of the inhaler liquid reservoir structure according to Figures 2 and 3.

Figure 4B is a cross section view of the airflow member shown in Figure 4A.

Figure 5 is schematic diagram showing a piezoelectric transducer modelled as an RLC circuit.

Figure 6 is graph of frequency versus log impedance of an RLC circuit.

Figure 7 is graph of frequency versus log impedance showing inductive and capacitive regions of operation of a piezoelectric transducer.

Figure 8 is flow diagram showing the operation of a frequency controller.

Figure 9 is a diagrammatic perspective view of a mist generator device of this disclosure.

Figure 10 is a diagrammatic perspective view of a mist generator device of this disclosure.

Figure 11 is a diagrammatic exploded perspective view of a mist generator device of this disclosure.

Figure 12 is a diagrammatic perspective view of a transducer holder of this disclosure.

Figure 13 is a diagrammatic perspective view of a transducer holder of this disclosure.

Figure 14 is a diagrammatic perspective view of a capillary element of this disclosure. 7 Figure 15 is a diagrammatic perspective view of a capillary element of this disclosure.

Figure 16 is a diagrammatic perspective view of a transducer holder of this disclosure.

Figure 17 is a diagrammatic perspective view of a transducer holder of this disclosure.

Figure 18 is a diagrammatic perspective view of a part of a housing of this disclosure.

Figure 19 is a diagrammatic perspective view of an absorbent element of this disclosure.

Figure 20 is a diagrammatic perspective view of a part of a housing of this disclosure.

Figure 21 is a diagrammatic perspective view of a part of a housing of this disclosure.

Figure 22 is a diagrammatic perspective view of an absorbent element of this disclosure.

Figure 23 is a diagrammatic perspective view of a part of a housing of this disclosure.

Figure 24 is a diagrammatic perspective view of a part of a housing of this disclosure.

Figure 25 is a diagrammatic perspective view of a part of a housing of this disclosure.

Figure 26 is a diagrammatic perspective view of a circuit board of this disclosure.

Figure 27 is a diagrammatic perspective view of a circuit board of this disclosure.

Figure 28 is a diagrammatic exploded perspective view of a mist generator device of this disclosure.

Figure 29 is a diagrammatic exploded perspective view of a mist generator device of this disclosure.

Figure 30 is a cross sectional view of a mist generator device of this disclosure.

Figure 31 is a cross sectional view of a mist generator device of this disclosure. 8 Figure 32 is a cross sectional view of a mist generator device of this disclosure.

Figure 33 is a diagrammatic perspective view of a hookah device of this disclosure.

Figure 34 is a diagrammatic perspective view of a hookah device of this disclosure attached to a hookah body and water bowl of a hookah apparatus.

Figure 35 is a diagrammatic exploded perspective view of a hookah device of this disclosure.

Figure 36 is a diagrammatic perspective view of components of a hookah device of this disclosure.

Figure 37 is a diagrammatic perspective view of components of a hookah device of this disclosure.

Figure 38 is a diagrammatic perspective view of a component of a hookah device of this disclosure.

Figure 39 is a diagrammatic perspective view of a component of a hookah device of this disclosure.

Figure 40 is a diagrammatic perspective view of a component of a hookah device and four mist generator devices of this disclosure.

Figure 41 is a diagrammatic perspective view of components of a hookah device of this disclosure.

Figure 42 is a diagrammatic cross-sectional view of components of a hookah device of this disclosure.

Figure 43 is a diagrammatic perspective view of a hookah device of this disclosure attached to a hookah body and water bowl of a hookah apparatus.

Detailed description Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 9 The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components, concentrations, applications and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the attachment of a first feature and a second feature in the description that follows may include embodiments in which the first feature and the second feature are attached in direct contact, and may also include embodiments in which additional features may be positioned between the first feature and the second feature, such that the first feature and the second feature may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

The following disclosure describes representative arrangements or examples.

Each arrangement or example may be considered to be an embodiment and any reference to an "arrangement" or an "example" may be changed to "embodiment" in the present disclosure.

A hookah device of some arrangements incorporates ultrasonic aerosolization technology. The hookah device of some arrangements is configured to replace a conventional hookah head (coal-heated or electronically heated). The hookah device of some arrangements releasably attaches to an existing stem or metal body and water chamber/bowl in place of the conventional hookah head which houses the tobacco and the charcoal (or electronic heating element).

In other arrangements, the hookah device is provided with a stem/body and a water chamber/bowl as a complete hookah apparatus.

Hookah water bowls come in various shapes and sizes, ornamented with traditional or futuristic decorations as per individual preferences. The design and development of the ultrasonic aerosolizing hookah device of some arrangements was executed, keeping the tradition in mind, to create a replaceable head that fits onto any existing hookah.

The following disclosure describes the components and functionality of an ultrasonic mist generator device. The disclosure then describes the hookah device of some arrangements which incorporates a plurality of ultrasonic mist generator devices.

Conventional electronic vaporizing inhalers tend to rely on inducing high temperatures of a metal component configured to heat a liquid in the inhaler, thus vaporizing the liquid that can be breathed in. The liquid typically contains nicotine and flavorings blended into a solution of propylene glycol (PG) and vegetable glycerin (VG), which is vaporized via a heating component at high temperatures. Problems with conventional inhalers may include the possibility of burning metal and subsequent breathing in of the metal along with the burnt liquid. In addition, some may not prefer the burnt smell or taste caused by the heated liquid.

Figures 1 to 4 illustrate an ultrasonic mist inhaler comprising a sonication chamber. It is noted that the expression "mist" used in the following disclosure means the liquid is not heated as usually in traditional inhalers known from the prior art. In fact, traditional inhalers use heating elements to heat the liquid above its boiling temperature to produce a vapor, which is different from a mist.

When sonicating liquids at high intensities, the sound waves that propagate into the liquid media result in alternating high-pressure (compression) and low- pressure (rarefaction) cycles, at different rates depending on the frequency.

During the low-pressure cycle, high-intensity ultrasonic waves create small vacuum bubbles or voids in the liquid. This phenomenon is termed cavitation. 11 When the bubbles attain a volume at which they can no longer absorb energy, they collapse violently during a high-pressure cycle. During the implosion, very high pressures are reached locally. At cavitation, broken capillary waves are generated, and tiny droplets break the surface tension of the liquid and are quickly released into the air, taking mist form.

The following will explain more precisely the cavitation phenomenon.

When the liquid is atomized by ultrasonic vibrations, micro water bubbles are produced in the liquid.

The bubble production is a process of formation of cavities created by the negative pressure generated by intense ultrasonic waves generated by the means of ultrasonic vibrations.

High intensity ultrasonic sound waves leading to rapid growth of cavities with relatively low and negligible reduction in cavity size during the positive pressure cycle.

Ultrasound waves, like all sound waves, consist of cycles of compression and expansion. When in contact with a liquid, Compression cycles exert a positive pressure on the liquid, pushing the molecules together. Expansion cycles exert a negative pressure, pulling the molecules away from another.

Intense ultrasound waves create regions of positive pressure and negative pressure. A cavity can form and grow during the episodes of negative pressure.

When the cavity attains a critical size, the cavity implodes.

The amount of negative pressure needed depends on the type and purity of the liquid. For truly pure liquids, tensile strengths are so great that available ultrasound generators cannot produce enough negative pressure to make cavities. In pure water, for instance, more than 1,000 atmospheres of negative 12 pressure would be required, yet the most powerful ultrasound generators produce only about 50 atmospheres of negative pressure. The tensile strength of liquids is reduced by the gas trapped within the crevices of the liquid particles. The effect is analogous to the reduction in strength that occurs from cracks in solid materials. When a crevice filled with gas is exposed to a negative-pressure cycle from a sound wave, the reduced pressure makes the gas in the crevice expand until a small bubble is released into solution.

However, a bubble irradiated with ultrasound continually absorbs energy from alternating compression and expansion cycles of the sound wave. These cause the bubbles to grow and contract, striking a dynamic balance between the void inside the bubble and the liquid outside. In some cases, ultrasonic waves will sustain a bubble that simply oscillates in size. In other cases, the average size of the bubble will increase.

Cavity growth depends on the intensity of sound. High-intensity ultrasound can expand the cavity so rapidly during the negative-pressure cycle that the cavity never has a chance to shrink during the positive-pressure cycle. In this process, cavities can grow rapidly in the course of a single cycle of sound.

For low-intensity ultrasound the size of the cavity oscillates in phase with the expansion and compression cycles. The surface of a cavity produced by low- intensity ultrasound is slightly greater during expansion cycles than during compression cycles. Since the amount of gas that diffuses in or out of the cavity depends on the surface area, diffusion into the cavity during expansion cycles will be slightly greater than diffusion out during compression cycles. For each cycle of sound, then, the cavity expands a little more than it shrinks. Over many cycles the cavities will grow slowly.

It has been noticed that the growing cavity can eventually reach a critical size where it will most efficiently absorb energy from the ultrasound. The critical size depends on the frequency of the ultrasound wave. Once a cavity has 13 experienced a very rapid growth caused by high intensity ultrasound, it can no longer absorb energy as efficiently from the sound waves. Without this energy input the cavity can no longer sustain itself. The liquid rushes in and the cavity implodes due to a non-linear response.

The energy released from the implosion causes the liquid to be fragmented into microscopic particles which are dispersed into the air as mist.

The equation for description of the above non-linear response phenomenon may be described by the "Rayleigh-Plesset" equation. This equation can be derived from the "Navier-Stokes" equation used in fluid dynamics.

The inventors approach was to rewrite the "Rayleigh-Plesset" equation in which the bubble volume, V, is used as the dynamic parameter and where the physics describing the dissipation is identical to that used in the more classical form where the radius is the dynamic parameter.

The equation used derived as follows: 2 1

Claims

CLAIMED IS:

1. A hookah device for use with a hookah having an elongate stem and a water chamber with a first end of the stem attached to the water chamber, wherein the hookah device comprises: 10 a plurality of ultrasonic mist generator devices which are each provided with a respective mist outlet port; a driver device which is connected electrically to each of the mist generator devices and configured to activate the mist generator devices; and a hookah attachment arrangement which is configured to attach the 15 hookah device to a second end of the stem of the hookah, the hookah attachment arrangement having a hookah outlet port which provides a fluid flow path from the mist outlet ports of the mist generator devices and out of the hookah device such that, when at least one of the mist generator devices is activated by the driver device, mist generated by each activated mist generator 20 device flows along the fluid flow path and out of the hookah device to the hookah.

2. The hookah device of claim 1, wherein the driver device is connected electrically to each of the mist generator devices by a data bus and the driver 25 device is configured to identify and control each mist generator device using a respective unique identifier for the mist generator device.

3. The hookah device of claim 1 or claim 2, wherein each mist generator device comprises: 30 an identification arrangement comprising: an integrated circuit having a memory which stores a unique identifier for the mist generator device; and an electrical connection which provides an electronic interface for communication with the integrated circuit. 35 64 5

4. The hookah device of any one of the preceding claims, wherein the driver device is configured to control each respective mist generator device to activate independently of the other mist generator devices.

5. The hookah device of claim 4, wherein the driver device is configured to 10 control the mist generator devices to activate in a predetermined sequence.

6. The hookah device of any one of the preceding claims, wherein each mist generator device comprises: a manifold having a manifold pipe which is in fluid communication with 15 the mist outlet ports of the mist generator devices, wherein mist output from the mist outlet ports combines in the manifold pipe and flows through the manifold pipe and out from the hookah device.

7. The hookah device of claim 6, wherein the hookah device comprises 20 four mist generator devices which are releasably coupled to the manifold at 90º relative to one another.

8. The hookah device of any one of the preceding claims, wherein each mist generator device is releasably attached to the driver device so that each 25 mist generator device is separable from the driver device.

9. The hookah device of any one of the preceding claims, wherein each mist generator device comprises: a mist generator housing which is elongate and comprises an air inlet 30 port and the said mist outlet port; a liquid chamber provided within the mist generator housing, the liquid chamber containing a liquid to be atomized; a sonication chamber provided within the mist generator housing; a capillary element extending between the liquid chamber and the 35 sonication chamber such that a first portion of the capillary element is within the 65 5 liquid chamber and a second portion of the capillary element is within the sonication chamber; an ultrasonic transducer having a generally planar atomization surface which is provided within the sonication chamber, the ultrasonic transducer being mounted within the mist generator housing such that the plane of the 10 atomization surface is substantially parallel with a longitudinal length of the mist generator housing, wherein part of the second portion of the capillary element is superimposed on part of the atomization surface, and wherein the ultrasonic transducer is configured to vibrate the atomization surface to atomize a liquid carried by the second portion of the capillary element to generate a mist 15 comprising the atomized liquid and air within the sonication chamber; and an airflow arrangement which provides an air flow path between the air inlet port, the sonication chamber and the air outlet port.

10. The hookah device of claim 9, wherein each mist generator device 20 further comprises: a transducer holder which is held within the mist generator housing, wherein the transducer element holds the ultrasonic transducer and retains the second portion of the capillary element superimposed on part of the atomization surface; and 25 a divider portion which provides a barrier between the liquid chamber and the sonication chamber, wherein the divider portion comprises a capillary aperture through which part of the first portion of the capillary element extends.

11. The hookah device of claim 9 or claim 10, wherein the capillary element 30 is 100% bamboo fiber.

12. The hookah device of any one of claims 9 to 11, wherein the airflow arrangement is configured to change the direction of a flow of air along the air flow path such that the flow of air is substantially perpendicular to the 35 atomization surface of the ultrasonic transducer as the flow of air passes into the sonication chamber. 66 5

13. The hookah device of any one of claims 9 to 12, wherein the liquid chamber contains a liquid having a kinematic viscosity between 1.05 Pa•s and

14.412 Pa•s and a liquid density between 1.1 g/ml and 1.3 g/ml. 10 14. The hookah device of any one of claims 9 to 13, wherein the liquid chamber contains a liquid comprising approximately a 2:1 molar ratio of levulinic acid to nicotine.

15. The hookah device of any one of the preceding claims, wherein the 15 driver device comprises: an AC driver which is configured to generate an AC drive signal at a predetermined frequency to drive a respective ultrasonic transducer in each mist generator device; an active power monitoring arrangement which is configured to monitor 20 the active power used by the ultrasonic transducer when the ultrasonic transducer is driven by the AC drive signal, wherein the active power monitoring arrangement is configured to provide a monitoring signal which is indicative of an active power used by the ultrasonic transducer; a processor which is configured to control the AC driver and to receive 25 the monitoring signal drive from the active power monitoring arrangement; and a memory storing instructions which, when executed by the processor, cause the processor to: A. control the AC driver to output an AC drive signal to the ultrasonic transducer at a predetermined sweep frequency; 30 B. calculate the active power being used by the ultrasonic transducer based on the monitoring signal; C. control the AC driver to modulate the AC drive signal to maximize the active power being used by the ultrasonic transducer; D. store a record in the memory of the maximum active power 35 used by the ultrasonic transducer and the sweep frequency of the AC drive signal; 67 5 E. repeat steps A-D for a predetermined number of iterations with the sweep frequency incrementing with each iteration such that, after the predetermined number of iterations has occurred, the sweep frequency has been incremented from a start sweep frequency to an end sweep frequency; 10 F. identify from the records stored in the memory the optimum frequency for the AC drive signal which is the sweep frequency of the AC drive signal at which a maximum active power is used by the ultrasonic transducer; and G. control the AC driver to output an AC drive signal to the 15 ultrasonic transducer at the optimum frequency to drive the ultrasonic transducer to atomize a liquid.

16. The hookah device of claim 15, wherein the active power monitoring arrangement comprises: 20 a current sensing arrangement which is configured to sense a drive current of the AC drive signal driving the ultrasonic transducer, wherein the active power monitoring arrangement is configured to provide a monitoring signal which is indicative of the sensed drive current. 25

17. The hookah device of claim 15 or claim 16, wherein the memory stores instructions which, when executed by the processor, cause the processor to: repeat steps A-D with the sweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 2960kHz. 30

18. The hookah device of claim 15 or claim 16, wherein the memory stores instructions which, when executed by the processor, cause the processor to: repeat steps A-D with the sweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 3100kHz. 68 5

19. The hookah device of any one of claims 15 to 18, wherein the AC driver is configured to modulate the AC drive signal by pulse width modulation to maximize the active power being used by the ultrasonic transducer.

20. A hookah comprising: 10 a water chamber; an elongate stem having a first end which is attached to the water chamber, the stem comprising a mist flow path which extends from a second end of the stem, through the stem, to the first end; and a hookah device according to any one of the preceding claims, wherein 15 the hookah attachment arrangement of the hookah device is attached to the stem of the hookah at the second end of the stem. 69