Can I use anova on values in decibel (logaritmic)? I'm doing a project where I'm measuring outdoor sound in different spots. I've repeated the measurement 3 times at every spot on different days (with different weather etc). I measure every spot for 10 minutes and the sound level meter give me one value (in dBA, A-weighted decibels) every second. Now I want to do a statistical analysis on these values to compare and see if there's a statistical difference depending on the day/weather.
Can I do an anova-test on the decibel-values directly, do I need to convert them, or what do I do? I'm asking since decibel is made by a logaritmic function ... Hence you can't really add 1 dB + 1 dB, since it really become 3 dB ... So the mean value won't be 'correct'. 
Hope someone understand what I mean ... 
Adding a bit for one of the places I've measured at and the data comparison between the spots I've measured. These measurments are made the same day: 

As you can see spot 5 and 2 aren't significantly different while spot 2 and 3 are. The dBA-equivalent for spot 5 and 3 is 60,2 dBA and for spot 2 it's 58,4 dBA.
Shouldn't the anova/the tukey-kramer test show the same for the two comparisons?
Below is the measured values (dB) over time. I've measured for 10 minutes in each spot (point), that is located in different areas of a bigger area (school yard). 

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 A: I would say you can use anova for analyzing noise level measurements, see this stored google search which links many papers using anova in the analysis of noise measurements. 
As you say, noise measurements in decibel cannot really be added, say, if the problem is finding the resultant noise level from two simultaneous independent sources, like a jet taking off close the the noisy highway you're on. 
But that is not your problem. You are making a statistical comparison of the noise levels under different conditions, comparing different distributions of noise levels. Your interest is in parameters of those noise level distributions, which is a very different problem from the technical problem of adding noise from independent, simultaneous sources. So, I guess it is more relevant to ask if the distribution of noise levels are sufficiently symmetrical/close to normal, so that the mean is a good statistical parameter. 
For some related discussion see What is the terminology for data aggregated via summed totals versus data aggregated via means? 
EDIT

After you added the ANOVA example with data: I would suspect that the repeat measurements, the same day, same spot, are autocorrelated, so you should not treat them as independent observations, as you have done. Can you add some time series plot, or autocorrelations? (by site)
