# Getting precise dB level from Playback meter reading

Is there an analysis tool I’m missing, that gives the numeric number of the dB level as indicated on the blue line for a whole track? I want something that will give me the number without having to play the file and see how high & where the blue line ends up. Like Plot Spectrum, but with exact correspondence, if that makes any sense.
TIA

If you run the Amplify effect it will “indirectly” give you the peak. Audacity has already scanned your file and Amplify will default to whatever gain (or attenuation) is needed for normalized/maximized 0dB peaks. i.e. If Amplify defaults to +3dB, your current peak is -3dB.

[u]ACX Check[/u] will give you the peak and RMS levels.

There is a 3rd-party plug-in called [u]dpMeter[/u] that can give you EBU R128 loudness.

oh, duh, thanks!

I don’t even know what that means… I know what it stands for, but I’ve forgotten everything I supposedly learned in Algebra II. I’m doing all I can do as maths-free as possible, lol.

Root Mean Square. Area under the curve. In power systems, this is the ability to perform work—make a motor go 'round.

Somebody figured out that the RMS of a sound signal happened to correspond roughly to loudness. That gives you: “You failed your audiobook test because your RMS wasn’t high enough.”

“You weren’t loud enough.”

That’s not the only way to measure loudness and it’s not even particularly good, but it’s one of the few traceable back to common sound engineering practices.

Koz

Missed one. Analyze > Contrast > Measure Selection will give you the RMS values.

Koz

RMS is a kind of average and it correlates better with perceived loudness than the peak levels. (The regular average is zero because the waveform is negative half of the time.) Our ears don’t hear occasional short-duration peaks as loud as loudly as multiple-sustained peaks.

Generally, it’s the peaks that we are concerned with because analog-to-digital converters (recording), digital-to-analog converters (playback) and regular WAV files and audio CDs are all hard-limited to 0dB and you’ll get clipping (distorted squared-off waves) if you try to go over.

EBU R128 (AKA LUFS) takes it a step further and takes-into account the fact that our ears are most-sensitive at mid-frequencies.

P.S.
Another “interesting fact” about RMS - If the energy (wattage) from RMS voltage is equal to the same DC voltage. Here in the U.S. household voltage is 120VAC RMS. With a 120V sine wave you have positive & negative peaks of about 170V, and of course it passes-through zero twice per cycle. A regular 100W incandescent light blub will glow at the same brightness (and consume the same 100W of power) if you apply 120VDC.

The average of the absolute values is a little less than the RMS (for a sine wave).

AC voltmeters measure RMS voltage, so if you check the wall voltage you’ll get (about) 120VAC.

Of course, regular audio (voice & music) isn’t a pure sine wave. The peak-to-RMS ratio is greater and it depends on the particular recording (and the amount of dynamic compression, etc.).

Here’s a Nyquist plug-in that will give you the peak and RMS levels for each selection.