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647 views
05:47 Jul-27-1999
Simon Griffin
Air/gas transmission

'Gases are generally rather attenuating in the MHz range', Does anybody
have any tables or graphs representing this. After extensive searching
I cannot quantify this statement.

Regards

Simon Griffin B.Eng IoM


 
06:37 Jul-27-1999
Wieslaw Bicz
Re: Air/gas transmission : 'Gases are generally rather attenuating in the MHz range', Does anybody
: have any tables or graphs representing this. After extensive searching
: I cannot quantify this statement.

: Regards

: Simon Griffin B.Eng IoM

You can find some tables and graphs in Landold Börnstein: Molecular Acoustics or in older books (written about 1930).
It is difficult to find such data in newer books. If you are interested, I can send you the copies of such tables.

But you must know - if you will test sound propagation in air, it will be difficult to make reliable measurements with frequencies higher then about 2 MHz under
normal atmospheric condistions (without higner pressure). We have made some experiments with such frequencies and the results are not easy to compare.

You will need to find a good method for such measurements.

Sincerely


 
00:00 Jul-28-1999

Robert (Rocky) A. Day

Engineering
Milky Way Jewels,
USA,
Joined Nov 1998
40
Re: Air/gas transmission Try to get Eric Ash's book 'Scanned Image Microscopy' and in is an article by Kumar Wickramasinghe and C. Petts on 'Gas Medium Acoustic Microscopy' with data as a function of pressure for several gases. Has some references that may also be useful. Their data goes to 40 MHz and 200 bars.

: 'Gases are generally rather attenuating in the MHz range', Does anybody
: have any tables or graphs representing this. After extensive searching
: I cannot quantify this statement.

: Regards

: Simon Griffin B.Eng IoM




 
08:11 Sep-02-1999

Leon Vandervalk

R & D
DeFelsko Corporation,
USA,
Joined Oct 1999
3
Re: Air/gas transmission You may want to contact the folks at VN Instruments.
http://www.vninstruments.com
These guys have built some very impressive air coupled ultrasonic instrumentation. I've seen some of the experimental data generated using their gear and recall seeing attenuation plots...


: : 'Gases are generally rather attenuating in the MHz range', Does anybody
: : have any tables or graphs representing this. After extensive searching
: : I cannot quantify this statement.

: : Regards

: : Simon Griffin B.Eng IoM

: You can find some tables and graphs in Landold Börnstein: Molecular Acoustics or in older books (written about 1930).
: It is difficult to find such data in newer books. If you are interested, I can send you the copies of such tables.

: But you must know - if you will test sound propagation in air, it will be difficult to make reliable measurements with frequencies higher then about 2 MHz under
: normal atmospheric condistions (without higner pressure). We have made some experimentswith such frequencies and the results are not easy to compare.

: You will need to find a good method for such measurements.

: Sincerely




 


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