Hey, i am working on a project where i am stucked with whether a ultrasonic segnal will pass through an aluminium foil or not?
Actually the project is i want to detect the presence of holes in the material (Aluminium foil) between ultrasonic transmitter and receiver.
So the first query is if there is a foil between transmitter and receiver then the transmitted ultrasonic wave will be able to travel through the foil or not??
Actually i dont want it to travel and the logic will be if any ultrasonic wave will be received at the receiver side then there must be a whole in it.
and if ultrasonic wave will not be able to pass through aluminium foil then there is no whole.(size of holes will be in microns)
If anyone has any idea. Please response and help me out.
Ultrasonic signals reflect signals as a function of the speed of sound change.
I've not tested this type of situation (all my experience is with single transmitter / receiver). I would guess very little sound would make it through the aluminum foil regardless of the number of holes.
Hi JohnRob,
Thankyou for your response. :))
Please read my query again (I editted it a bit), and can you suggest whether it is possible with Light sensor by transmitting light from one side and installing lots of receiver in other side.
How much sound or light passes through a small hole will depend on the size relative to wavelength, so i suspect that micron size holes won't transmit much ultrasound at the frequencies accessible with simple transducers. Light sounds much more likely as it will diffract through small holes. Consider a bright LED illuminator and a camera looking for transmitted light.
Some similarity to a pin-hole camera.
The pinhole will act to "lens" the point source from the other side of the foil, thus a single photodetector will be severely under illuminated unless critically positioned.
Really this is rather similar to star field photography. I gather that the latest phones can do pretty good astrophotographs. Have your foil sample in front of a bright light source such as an LED spotlight, with a LENS to focus light from any pinholes in the foil onto a CAMERA sensor. You want to gather the whole image so it doesn't matter where the hole is. Use a reasonably long exposure. Need to design the setup to avoid light leakage. Then some image processing to extract any dots that indicate holes.
So, there is a mountain of information on the Internet about why peoples eyes do not fry when watching food cook in a microwave oven. The answer is a high-level study of wave frequency and incident wavefront against a conductive surface.
