I think if the amplitude is large then the acoustic pressure also high.
I have tried to increase the acoustic pressure and use the ultrasonic booster which is known to increase amplitude.
But it did not work. The acoustic pressre measured by hydrophone was almost same as the acoustic pressure of the transducer without booster.
I am wondering
1. What is the relationship between the acoustic pressure and the amplitude.
2. What is the ultrasonic booster. Does it can increase the acoustic pressure??
The power is proportional to the amplitude times the pressure. If you don't increase the power you can't increase one without decreasing the other. You can't increase the power without an amplifier or another transducer. The ratio between pressure and amplitude is proportional to the impedance. A booster changes the impedance. If the impedance is right then all the power gets transmitted. If not then some of the power never makes it out of the transducer and is wasted.
Malcolm White Thanks a lot. then, can I ask you how to get "right" impedance? how can I check it? and make it?
Looking at the boosters on the page I linked to they are designed to give high amplitude to melt plastic. These will have low output impedance and probably are not useful to get a good match to water. I think you may find what you need on the website of the transducer manufacturer, who may have application notes about the use of transducers, or the website of the horn manufacturer. They may all be optimised for water, or IPA or MEBK.
Dear colleague,
by physics, sound is only the fraction of the pressure able to propagate without attenuation; it CANNOT be measured by a pressure probe in the nearfield of a sound source, which measure the total pressure, not the sound pressure!
The only way to assess the sound pressure in the nearfield of a sound source is to measure the pressure gradient (sound intensity probes), knowing the relationship between sound pressure and sound velocity P=RhoxCxV where rho is the acoustic medium density (1.3 kg/m3 in standard atmospheric condition), C the sound velocity (340m/s in a standard atmospheric condition) and V the sound velocity measured by the pressure gradient. In practice, this means you only retain the average pressure level between the two probes which is in quadrature (90° out-phasing) with the pressure gradient - as this is the condition to propagate as sound waves.
Alternatively, if you are able to measure the sound pressure of your device in the farfield (several metres) in free field propagation conditions (outdoor or in an anechoic chamber), you can also "retropropagate" it to estimate the sound pressure at 1m of the source by applying the freefield sound diffusion formula (invert square of the distance)
What you currently measures is the total dynamic pressure of the fluid, which includes turbulent fluid movements not turning effectively into sound: no surprise you cannot correlate it to the sound level of your device! They become furthermore present if you reaches the pressure level where things become non-linear (viscous effects, cavitation) because you aim at very high sound levels.
Sorry, I see you are in a fluid (oil or water?): replace the impedance values by those of this denser medium, but the physics are the same ! I am not sure commercial pressure gradiometres (sound intensity probes) exist for ultrasound, but conversely it is easier to get free field/farfield acoustic pressure measurements in a reasonably sized tank... The size of your pressure probe is a key issue, it must be small compared to the wavelength!
I think you may find what you need on the website of the transducer manufacturer, who may have application notes about the use of transducers, or the website of the horn manufacturer. They may all be optimised for water, or IPA or MEBK.
I am confused that Ca Dr. Gaurav Bhambri seems to have cut and pasted the last part of my reply, to make his entire comment, and then received 21 recommendations, while my original comment 4 months before received none.
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