What materials would produce an impedance mismatch?

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SUMMARY

This discussion centers on the creation of impedance mismatches to shield against ultrasound frequencies up to 3GHz traveling through air. The user seeks materials with an acoustic impedance of around 1.5 to 2, and references the need for an impedance of approximately 7 to effectively deflect ultrasound. The conversation highlights the lack of available research papers on this topic, particularly regarding military applications. Participants emphasize the challenges of working with high-frequency ultrasound in air and the necessity for further exploration of material properties.

PREREQUISITES
  • Understanding of acoustic impedance and its role in sound wave propagation
  • Familiarity with ultrasound frequency ranges, specifically from 20KHz to 3GHz
  • Knowledge of material properties that affect sound wave transmission
  • Basic principles of wave interference and reflection
NEXT STEPS
  • Research materials with high acoustic impedance, specifically those around 7
  • Investigate existing studies on ultrasound shielding techniques in military applications
  • Explore the effects of different materials on ultrasound transmission at varying frequencies
  • Learn about advanced acoustic engineering methods for creating impedance mismatches
USEFUL FOR

Acoustic engineers, materials scientists, and researchers focused on ultrasound applications and shielding techniques will benefit from this discussion.

mcriv880
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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.
 
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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.
 
mcriv880 said:
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 said:
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...
 
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.
 
mcriv880 said:
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?
 
berkeman said:
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.
 
mcriv880 said:
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.
 

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