AllenB no I haven't determined it yet because it depends on the surface to be crossed which is why I didn't talk about it, you tell me
You'll have to explain the concept to me because...
...because your above statement is incomplete, plus you didn't supply a link.
FROM WIKIPEDIA ENGLISH
"Acoustic resistance represents the energy transfer of an acoustic wave. The pressure and motion are in phase, so work is done on the medium ahead of the wave. Acoustic reactance represents the pressure that is out of phase with the motion and causes no average energy transfer.[citation needed] For example, a closed bulb connected to an organ pipe will have air moving into it and pressure, but they are out of phase so no net energy is transmitted into it. While the pressure rises, air moves in, and while it falls, it moves out, but the average pressure when the air moves in is the same as that when it moves out, so the power flows back and forth but with no time averaged energy transfer.[citation needed] A further electrical analogy is a capacitor connected across a power line: current flows through the capacitor but it is out of phase with the voltage, so no net power is transmitted into it."
"Acoustic resistance represents the energy transfer of an acoustic wave. The pressure and motion are in phase, so work is done on the medium ahead of the wave. Acoustic reactance represents the pressure that is out of phase with the motion and causes no average energy transfer.[citation needed] For example, a closed bulb connected to an organ pipe will have air moving into it and pressure, but they are out of phase so no net energy is transmitted into it. While the pressure rises, air moves in, and while it falls, it moves out, but the average pressure when the air moves in is the same as that when it moves out, so the power flows back and forth but with no time averaged energy transfer.[citation needed] A further electrical analogy is a capacitor connected across a power line: current flows through the capacitor but it is out of phase with the voltage, so no net power is transmitted into it."
hi Andrew then considering the powers I think a 100 watt transducer could be fine, I could always move it away from the surface in case it was too powerful,
@Galu it is research that I have been carrying out for some time, I have attended various conferences and meetings on this topic, which is why I am talking about it with you, there are numerous articles about the help that ultrasound gives to the defense and growth of plants. So are there solutions with parabola or phase coupling?
sorry, maybe I'm wrong about the concept of the difference between speed and pressure, I ask for your clarification. however for the concept of the parabolic reflector which is a feasible solution, what can I do?
I certainly didn't understand what you meant by "phase coupling", even after reading your Wikipedia extract.
Even if armed with the full technical specifications of your ultrasonic transducer, I can't imagine how a parabolic reflector would overcome your air-soil acoustic impedance mismatch problem.
Sorry, this not my area of expertise. I started off well, hesitated in the middle and have now come to a stumbling halt! 🤓
Even if armed with the full technical specifications of your ultrasonic transducer, I can't imagine how a parabolic reflector would overcome your air-soil acoustic impedance mismatch problem.
Sorry, this not my area of expertise. I started off well, hesitated in the middle and have now come to a stumbling halt! 🤓
The phase change is located where the change in impedance occurs. Altering phase at the source changes nothing.
It's unclear why you're struggling to avoid one area and reach another. The problem seems purely geometric and something I'd expect you to fix, or at least to explain to us.
In any case I thought it would help to point out the directivity since it seems relevant to that.
Yes. There's nothing you can really do from the souce that affects a location based phenomenon.
This got me thinking that Rabbilo was considering combining sources of positional diversity, for whatever reason. This also made me think the plane waves wouldn't be achieving anything useful. At this stage I don't know.
This got me thinking that Rabbilo was considering combining sources of positional diversity, for whatever reason. This also made me think the plane waves wouldn't be achieving anything useful. At this stage I don't know.
@AllenB so the question of the phase was my personal thought, reading what wikipedia said but not sure if it was the right path. instead the question of the parabolic reflector is more considered, in this way by pointing the transducer on the reflector, the reflector reflects the focused wave on the ground in the form of a plane wave, so as to have less attenuation, tell me if it's ok
so the question of the phase was my personal thought, reading what wikipedia said but not sure if it was the right path. instead the question of the parabolic reflector is more considered, in this way by pointing the transducer on the reflector, the reflector reflects the focused wave on the ground in the form of a plane wave, so as to have less attenuation, tell me if it's ok
@AllenB yes the phase question was just my idea, however for the reflector that generates a plane wave, that is a more feasible idea. the plane wave having no points of incidence is not affected by the attenuation effect, if I find the original text that my friend sent me I will send it to you, wait
@AllenB this is the test of my friend:
"Do not place a clear reflector around the plant, because that will block the wind and the rain.
You have one point source of ultrasound, and I believe you want to make a cylinder of sound that will enclose the plant with an isotropic level of sound, that penetrates the surface of the soil from above, to about 30 mm depth.
A radiating wave, from a point source, can be converted to a parallel beam by a parabolic reflector. That is the same principal as a satellite receiver dish.
A dish reflector would point downwards from above the plant, with the transducer at the focus, pointing upwards at the dish. The diameter of the dish will keep some rain off the plant, but sunlight and wind will enter from the side.
The reflected wave will arrive at the soil surface as a plane wavefront, so it should penetrate the surface soil evenly. I would not expect the wave to be reflected efficiently from the soil surface, unless it was flat and wet. Energy will be dispersed and lost in an open-structured soil with a rough surface.
The height of the dish above the ground is not critical, it can be raised as the plant grows.
I expect the dish diameter will be about 300 mm, which is 10 wavelengths at 30 kHz ≈ 5° beam sides. The ratio of focal length, to the diameter of the dish, will be determined by the radiation pattern of the ultrasonic transducer selected. The theory is the same as that of microwave dish "illumination".
The transducer specification, and the power level required, have not been specified."
"Do not place a clear reflector around the plant, because that will block the wind and the rain.
You have one point source of ultrasound, and I believe you want to make a cylinder of sound that will enclose the plant with an isotropic level of sound, that penetrates the surface of the soil from above, to about 30 mm depth.
A radiating wave, from a point source, can be converted to a parallel beam by a parabolic reflector. That is the same principal as a satellite receiver dish.
A dish reflector would point downwards from above the plant, with the transducer at the focus, pointing upwards at the dish. The diameter of the dish will keep some rain off the plant, but sunlight and wind will enter from the side.
The reflected wave will arrive at the soil surface as a plane wavefront, so it should penetrate the surface soil evenly. I would not expect the wave to be reflected efficiently from the soil surface, unless it was flat and wet. Energy will be dispersed and lost in an open-structured soil with a rough surface.
The height of the dish above the ground is not critical, it can be raised as the plant grows.
I expect the dish diameter will be about 300 mm, which is 10 wavelengths at 30 kHz ≈ 5° beam sides. The ratio of focal length, to the diameter of the dish, will be determined by the radiation pattern of the ultrasonic transducer selected. The theory is the same as that of microwave dish "illumination".
The transducer specification, and the power level required, have not been specified."