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Noise Reduction Graphs

i have this graph generated by the noise reduction software. Can help clarify why it stated there's a 2 dB correction applied?

Thank you.



please look at the "Calculations" view in the Sound Insulation Reporter software. In that view, please click on the "Average L2" calculation.

You'll see a graph similar to this one:

The L2 level average is getting close to the background noise at certain frequency bands. In this example there's a +6dB area on top of the background noise.

When the L2 average overlaps with that 6dB area above the background noise, the applied standard requires to process some correction values on the L2 measurments.

The width of that area as well as the amount of correction varies from standard to standard, and sometimes even  within different versions of a standard.

Here's a description of that calculation in the ASTM E336 Standard you are using for version 2017 and 2020

ASTM E336 Version 2017

ASTM E336 Version 2020

You may download the full standard from here

I hope this helps.

Best Regards,


Gregor Schmidle

NTi Audio

Thank you very much Gregor, that's very helpful and clear. Really appreciate this.


Wan Li


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