Problem with Excel: ETC relative level w/Room Capture (-LOG)

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Problem with Excel: ETC relative level w/Room Capture (-LOG)

Postby DCR1986 » Fri Oct 28, 2011 2:52 pm


I am creating an Excel spreadsheet allows user to import Energy Time Curve data from 'Room Capture' into Excel.

The data import and separation is fine. I have the time (ms) and the relative level (Pa). I need to convert this level (Pa) information into dB in order to use it with a graph. I understand the conversion from dB -> Pa and Pa -> dB and that using this equation with minus numbers comes out complex (You can't have negative pressure)... However, using a graph I found in Sound Reproduction by Floyd E Toole (2008) there is a way of converting this information into dB which makes it plottable on a graph. In fact, the values should mostly be negative. The graph starts at 20dB down to -50dB on the y axis and 0 - 80 ms (delay) on the x axis. Here we can display the primary and secondary images equally loud (Haas 1972), Second image audible (Lochner & Berger, 1958), Shift or spreading of primary image (Olive & Toole, 1989) and Detection threshold (Olive & Toole, 1989) and fit the ETC over the top, focussing on the first 80ms as the important information.

Basically, I don't understand how to convert the Pa data which ranges from +800Pa to -800Pa roughly, and what equation is needed to transfer this to Relative Level (Pa) and also is it possible to perform LOG functions with negative numbers in Excel without it becoming complex.

Has anyone done anything like this who could offer some help, or anyone aware of/read the book Sound Reproduction by Floyd E Toole (2008) [graph on page 78 Chapter 6])

Here is a copy of the graph:

Thanks, David
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