how to read the result of level dectector ? (adau1701)

Sorry for the delayed response to your question. There are a few posts on this forum (links below) that will help you to understand the method for doing this.

You'll need to use the DSP Readback cell, not a level detector. An explanation of how to use the DSP Readback cell in conjunction with  an Envelope cell to read the average level of a signal is here:  http://ez.analog.com/message/7669#7669

On generation 3 SigmaDSPs, the result is 5.23 format (28 bits), but on the ADAU1701, the result is 5.19 (24 bits). A description of number formats is here: http://ez.analog.com/message/13377#13377

There is an example of how to do this using the Capture Window, explained in my post, here: http://ez.analog.com/message/21669#21669

The datasheet also describes the operation of the data capture registers on page 38, although this might be too much detail: http://www.analog.com/static/imported-files/data_sheets/ADAU1701.pdf

So, in summary, the easiest way to do what you want is to use the DSP Readback cell in SigmaStudio and duplicate the register write and read sequence shown in the Capture Window when you click the "Read" button. The result will be in 5.19 format.