linear amplitude scaling, or, linear loudness scaling (with Excel)

history, inside the problem, the software, how to use, examples, donations

Fig.1, amplification of 2nd data set to compare with first one

History

  Loudness scaling, amplitude scaling and linear scaling were used extensively in audio and sound analysis, in vibration analysis, in images analysis and in electronics for signal comparison.

  In this case we use those concepts in a different manner. Having 2 dataset coming from a measurement replicate or from a measure set with different instruments on the same sample, we make "amplification" of the 2^nd data set to compare with the first one.

  In Fig.1 it is shown the problem, and on the upper right the solution with this software.

  Probably there are routines for Matlab/Octave and for "R" devoted to scaling your values. But it is still difficult for my students to grasp all parameters used in those routines and often the subtended errors.

  Accounting all I said previously, I have selected Excel to solve those small problems. As reference you can see:

1. from M.D. Trifunac, CalTech University; the scaling is an important step in earthquake study, also in Fourier analysis,
2. the book of Manthos G. Papadopoulos et al.; with title Linear-Scaling Techniques in Computational Chemistry and Physics,
3. in the book of John Enderle at al.; you can find a simple description of linear scaling, in page 585 of Introduction to Biomedical Engineering,
4. from T. Brand, University of Oldenburg; a congress presentation on Loudness Scaling in audio engineering field,

Inside the Problem

  In the Fig.1 you can see the blue line, the raw data. The main peak probably stays at 205nm with absorbance near 2.3 but the replicate shows low Abs value and to compare them we need an amplification of the purple spectra.

  Is better to spent some time on the blue-purple superimposition:

1. if you obtain the "same" curve, in IC, in HPLC or in UV-Vis is better, the software is doing an artificial amplification, mathematical, surely with some distortion,
2. always make a chart of the 2 curves, the first plot as comparison, the second plot to see what changes with different parameters setting,
3. the 2 curves coming from different instruments or from replicates, so it is practically impossible superimposed, you must select if it is better to obtain the same values for highest peak, or as in Fig.1 produce a similar shoulder

The Software

  This free software was distributed under Creative Commons Public License, CCPL 3.0, see my Copyright web page. Please read accurately the Liability Waiver in red.

  There is only one version working on MS-Excel 2000, up to MS-Excel 2003, was tested on MS-Excel 2007 and 2010 version. Are available:

• the software itself, GVisco_linear-loudness-scaling-1.37.xls, (729 KB)
• a file with 2 examples, from UV-Vis spectrometer, this SCsources.xls, (167 KB)

How To Use

  Dear students, this is not an Excel course, so you should already know how to use formulae and functions. I remember you to pass every lesson of Excel 2003 in this Course, and after that, do pass all the lessons of 2010 version (and do ALL projects).

  Very often the writer of the software is not the best writer of "instructions", he/she already knows how to use it! Nevertheless, I have made here a tentative to describe how proceed:

• first download the SCsources.xls file with examples and open it in Excel,
• download the GVisco_linear-loudness-scaling-1.37.xls file and open in Excel,
• copy your data with PasteSpecial/Values (or PasteSpecial/Text) in the "raw" sheet pointing to A9,
• the column A held the X values, the column B held the Y values (for references only), the C column held the working data,
• be careful, only the column C is for working data set, the A and B are for reference only and to design the chart,
• there is space for 1421 values and if you know well Excel you must/can add or remove rows to fit your data,
• do not touch any other cells in the "raw" sheet and in the "calc" sheet, pass to "chart" sheet,
• the spreadsheet is already filled with an example,

Fig.2, the Scaling parameter on the left with pointing cells, and the Solver options on the right

• do not touch any other cells in the "chart" sheet, see the Fig.2 with the yellow cells to be filled,
• starting with the red cells, the C6 and C7 shown the calculated min and max for Y2 data. The cells E6 and E7 shown the values after corrections,
• in the cell E8 you can insert a multiplier, suggested 1, for minimum. This can be useful to correct a baseline error,
• the cell E10 is devoted to multiplier for the max values, the main work of this software. Suggested values come from 0.7 to 1.3. ,
• the results of computation can be round off with the value of cell E11,
• in some instruments the output values are quantized (as example with step of 0.25, 0.1 or similar one), the cell E12 simulated the quantization on calculated values,
• finally the cell E9 can be used to move up and down the computed final results,
•  
• the results, as you see, are in the column D of "calc" sheet, the rounded ones are in the column E, and the results quantized are in the column F of "calc" sheet,
• remember to use Copy from column D and PasteSpecial/Values (or PasteSpecial/Text) in your new spreadsheet.

Examples

  As an example I have produced the file SCsources.xls . The columns B and C are an example, the columns D and E other one.

  The column B and C refer to an UV-Vis measurement campaign in the Roman Forum. The spring water of Lacus Iuturnae was measured with 100mm quartz suprasil cuvette, every 0.5 nm, with Lambda 16 Perkin Elmer spectrophotometer.

  The column D and E refer to an exercise with students on ancient dyes.

  For the 2 example the columns B and D are the references values, and the columns C and E are the data to be modified with scaling.

Tips

  If you know Excel you can expand or reduce the 1421 rows, and probably design a better solution.

Donations if you have a Bitcoin wallet

  If you have a nice fat wallet you can send a few cents to this code 1ETv1mJTZTB7EiXwZkucF2BTA512Rkaw6 maybe with a message (be careful to the transaction cost, send 0.1 and pay 0.01 is not a good idea).

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Donations if you have not a Bitcoin wallet

  If you like this work and measures you can make a small donation of Bitcoin. You do not need a wallet to make a donation, indeed even those who have Bitcoin wallet is better to pass for a web site that "gift" currency since this does not have a transaction cost.

  To make a donation you must use some of your web-time. Go to www.GreenBitCo.in, enter my code 1ETv1mJTZTB7EiXwZkucF2BTA512Rkaw6 enter the Captcha code that you see, press "Claim Now" button. Wait 15 minutes on the publicity page, when the 15 minutes pass fill the new Captcha and press "Claim Now" again. To get some value are necessary 10 pages or more. Be careful, do not use roulette, dices, casino and other stealing web site.

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