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Technical Discussions
wang
wang
07:54 Aug-25-2008
who can tell me this formula's unit?

who can tell me this formula's unit?
N=V/£¨15.16F sin2(¦Ã)), { british standard [BS EN 12668-2:2001]}
N:nearfied length unit=?
V:sound velocity of the circular transducer unit=?
¦Ã:divergence unit=?
F:centre frequency unit=?
15.16: ?



    
 
 Reply 
 
Navita
Navita
00:32 Aug-25-2008
Re: who can tell me this formula's unit?
All dimensions for calculation are in mm for length/ distance, Hz for frequency and seconds for time.

----------- Start Original Message -----------
: who can tell me this formula's unit?
: N=V/£¨15.16F sin2(¦Ã)), { british standard [BS EN 12668-2:2001]}
: N:nearfied length unit=?
: V:sound velocity of the circular transducer unit=?
: ¦Ã:divergence unit=?
: F:centre frequency unit=?
: 15.16: ?
------------ End Original Message ------------




    
 
 Reply 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 177

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
177
06:27 Aug-25-2008
Re: who can tell me this formula's unit?
The explanations by Navita on equation A.1 of European Standard EN 12668-2 are correct.

If you use mm/s for velocity and cycles/s = Hz for frequency you get mm for the near field length. The factor 15.16 and sin2(gamma) are dimensionless.

Please note, that the velocity of the block is addressed, not the velocity of the transducer.

Udo Schlengermann
Convener CEN/TC138/WG2

----------- Start Original Message -----------
: who can tell me this formula's unit?
: N=V/£¨15.16F sin2(¦Ã)), { british standard [BS EN 12668-2:2001]}
: N:nearfied length unit=?
: V:sound velocity of the circular transducer unit=?
: ¦Ã:divergence unit=?
: F:centre frequency unit=?
: 15.16: ?
------------ End Original Message ------------




    
 
 Reply 
 

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