topic Re: Conversion formula in SAS Health and Life Sciences

Conversion formula

deleted_user — Tue, 01 Apr 2008 16:41:38 GMT

I presently have a SAS dataset of audiograms with a numeric var named SPL. It contains values which represent sound pressure levels measured in decibels (dBSPL). I need to convert the values of SPL to sound pressure measured in Pa (Pascal) or uP (micropascals) and store the converted values for future analysis. Any idea how to help this novice do this in SAS?

Thanks

Re: Conversion formula

Doc_Duke — Wed, 02 Apr 2008 15:50:12 GMT

I found this bye google searching the internet for

convert dbspl to pascal units

"'Pa' is the abbreviation for Pascal, which is a unit of pressure that is equivalent to 93.9794 dB SPL (Sound Pressure Level)."

so, the SAS statement is
Pa=93.9794* ;

If you need to know how to save a pemanent SAS dataset, you probably need a short cours e on introductory SAS. Cody's book might be useful there.

Re: Conversion formula

deleted_user — Wed, 02 Apr 2008 19:23:53 GMT

Unfortunately its not that simple. This is decibled sound pressure with a reference pressure of 0.00002Pa, it is not a simple multiplicative conversion factor.

dbSPL = 20 * LOG10(Pa/0.00002)

So the conversion is going to be

X = Pressure in Pa
Y = Presseure in dbSPL

Y=20*LOG10(X/0.00002)

Y/20 = LOG10(X/0.00002)

10^(Y/20)=X/0.00002

X = 0.00002 * 10^(Y/20)

Or in SAS Functions

X = 0.00002 * (10**(Y/20))

Ike Eisenhauer

Message was edited by: WDEisenhauer

Re: Conversion formula

deleted_user — Thu, 03 Apr 2008 20:57:47 GMT

Thanks! I actually had the conversion coded as:
X = 20*(10**(Y/20))/1000000;

Same result, but your's looks cleaner.