What materials would produce an impedance mismatch?

[mcriv880]

sufficient enough to redirect/shield against ultrasound 1MHz being directed through the air. i know a vacuum would. What I'm questioning is if you had 2 layers of different materials stacked on top of each other what could prevent the ultrasound from reaching the 2nd layer assuming the 1st layer is on the outside. The acoustic impedance of the second layer is somewhere between 1.5 and 2.

 

[mcriv880]

I'm interested in methods of deflecting/shielding ultrasound up to 3GHz traveling through air as a medium. My search lead me to the study of creating impedance mismatches to affect sound wavess. I'm looking specifically for the acoustic impedance necessary to act as a shield of sorts for materials with an acoustic impedance around one and a half. Some of my searches have said an impedance of around 7 would suffice however I can not find any papers on such tests, and how various materials affected ultrasound traveling through air as a medium at different frequencies. I'm guessing that there have been tests in this area with military applications which would suffice if readily available. To my knowledge this is the best way to affect sound waves, if there are any other methods please feel free to share.

 

[berkeman]

sufficient enough to redirect/shield against ultrasound 1MHz being directed through the air. i know a vacuum would. What I'm questioning is if you had 2 layers of different materials stacked on top of each other what could prevent the ultrasound from reaching the 2nd layer assuming the 1st layer is on the outside. The acoustic impedance of the second layer is somewhere between 1.5 and 2.

I'm interested in methods of deflecting/shielding ultrasound up to 3GHz traveling through air as a medium. My search lead me to the study of creating impedance mismatches to affect sound wavess. I'm looking specifically for the acoustic impedance necessary to act as a shield of sorts for materials with an acoustic impedance around one and a half. Some of my searches have said an impedance of around 7 would suffice however I can not find any papers on such tests, and how various materials affected ultrasound traveling through air as a medium at different frequencies. I'm guessing that there have been tests in this area with military applications which would suffice if readily available. To my knowledge this is the best way to affect sound waves, if there are any other methods please feel free to share.

Can you say more about your application? Those are very high frequencies for ultrasound in air...

 

[mcriv880]

Yes I realize they are very high frequencies for air being above 1MHz but I was looking for the entire range from 20KHz-Above 1GHz with air as a medium. Not just one specific frequency.

 

[berkeman]

Yes I realize they are very high frequencies for air being above 1MHz but I was looking for the entire range from 20KHz-Above 1GHz with air as a medium. Not just one specific frequency.

Can you say anything about the application? What intensity range are you looking at?

 

[mcriv880]

Can you say anything about the application? What intensity range are you looking at?

https://docs.google.com/viewer?a=v&pid=explorer&srcid=0B-C2IpG-te-Lblhhd2V2eEh6WUk

Please see pages 20, and 25.

 

[berkeman]

https://docs.google.com/viewer?a=v&pid=explorer&srcid=0B-C2IpG-te-Lblhhd2V2eEh6WUk

Please see pages 20, and 25.

Ah, I understand. Thanks.

But sorry, we don't discuss dangerous activities/weapons here on the PF. Your threads on this subject are now closed.