k-Wave

1. Seongjun Park
   

   Member
   Joined: Mar '12
   Posts: 9

   Hello.

   It is amazing tool, but I have few quesions.
   To model sensor directivity of a large plane single element detector in 2D case, you averaged datas in the spatial direction. So its result was the function of time and angle and looks like Sinc function.

   1. I think this is just the same thing when pupil function of the transducer's aperature is fourier-transformed but with few assumptions. Is this the same thing? I means the diffraction phenomenon of transducer determines the sensor directivity?

   2. I think to calculate the effective pressure, projected areas onto a transducer plane need to be considered even though sensivity of the transducer is assumed to the same in whole surface of transdcer. So this projection area is also considered to model sensor directivity?

   Thank you.

   Posted 13 years ago #

2. bencox
   

   Developer
   Joined: Mar '10
   Posts: 292

   Hi Seongjun,

   That's right. Spatially for a single frequency wave you'll get a sinc(k_x x) shaped function, which is the Fourier transform of a rectangular pupil function (although I've never heard the term used in acoustics!) The directivity arises through the fact that a single frequency plane wave incident perpendicular to the transducer (grazing incidence) will - for a high enough spatial wavenumber - average to a small value across the transducer, whereas a plane wave incident normal to the transducer will sum coherently across it to a large value.

   Not sure I understand your second point. What do you mean by effective pressure?

   Ben

   Posted 13 years ago #

3. Seongjun Park
   

   Member
   Joined: Mar '12
   Posts: 9

   Hi Ben,

   Thank you. Actually, I am specializing in optics so I used that term 'pupil funtion'(especially used in Fourier Optics). Sorry for the confusing. Anyway in the second question, I thought that the total amount of energy passing through the finite sized element per unit time can be given by dot product of flux vector and element's area vector. So, I used the term 'effective'.

   Thank you.

   Sengjun Park

   Posted 13 years ago #

4. bencox
   

   Developer
   Joined: Mar '10
   Posts: 292

   Hi Sengjun,

   Thanks for clarifying. Given that definition of effective pressure, then I don't think it would give you the directivity. The dot product of the acoustic intensity (say) and the area vector would give you a cosine dependence on angle, not a sinc function.

   Ben

   Posted 13 years ago #

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