setting maximum decibel levels for playback

Using Windows 7 and current Audacity version. Totally new to Audacity and no sound engineering or music background.
Involved in a study where two pieces of classical piano music will be played, one at maximum 45 dB and one at maximum 60 dB, to compare reception by listeners.
Is there a way to set this maximum for a piece of music - I’ve played around with Effect>Amplitude setting but don’t think this is really doing what I want it to. The music is a little distorted also.
We will be plugging USB into player, amplifier and multiple speakers so all 10 subjects receive equal delivery. We can manually adjust the volume in the room and check this with dB meter, but need to ensure that neither piece can peak OVER the set limits. Amplitude setting in Audacity has a maximum of 50dB also, which prevents me setting it at 60dB.
Anyone able to help? Thank you and happy new year.

You may be interested in this phenomenon … https ://en.wikipedia.org/wiki/Fletcher–Munson_curves


The “amplify” effect sets volume of the entire track according to the loudest peak in that track,
( so one stray loud peak knocks everything out of whack ).
RMS normalization” gives a more reliable way of getting one track to be as loud as another.
“Replay gain” is better still, see … ReplayGain plug-in

Amplitude setting in Audacity has a maximum of 50dB also, which prevents me setting it at 60dB.

The digital dB scale uses a different reference from the acoustic dB scale and normally they are uncalibrated. i.e. The acoustic loudness depends on your playback volume control, the size of your amplifier & speakers, how close to the speakers you are, etc.

However, they are perfectly correlated - If you reduce the digital level by 10dB, the acoustic level will also be reduced by 10dB.

So, make two files. One normal file and one reduced by 15dB (Amplify by -15dB, which is attenuation.)

Adjust the normal one to play back at 60dB on your SPL meter and the other will play back at 45dB.**

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Acoustic levels are measure in dB SPL (decibels Sound Pressure Level) where 0dB SPL is approximately the threshold of hearing. So SPL values are positive.

Digital levels are measured in dBFS (Decibels Full Scale) where 0dBFS is the “digital maximum”. It’s the maximum you can “count to” with a given number of bits. So dBFS values are normally negative.**

Since we want to avoid [u]clipping[/u] (flat-top distorted waves) digital dB meters are usually peak-reading. Peak levels don’t correlate well with perceived loudness. If you normalize (“maximize”) all of your recordings for 0dB peaks they won’t sound equally loud. A 0dB peak piano recording won’t sound as loud as a 0dB “dense” hard-rock recording or a 0dB full orchestra.

SPL meters are normally [u]weighted[/u] and short-term averaged to better-correlate with human hearing.




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  • There is a reason I say reduce instead of increase… When you boost the volume you can end-up clipping the digital file (or your digital-to-analog converter) or your amplifier, etc. So depending on your setup, the volume may not increase linearly. But (assuming you are not clipping to begin with) volume decreases are linear and the acoustic level changes will track the digital/electronic level changes.

** Audacity uses floating-point which uses a different 0dB reference and for all intents and purposes it has no maximum or minimum. So, Audacity itself can go over 0dB without clipping. But if it does, and if you play-back at “full digital volume”, you’ll clip your DAC (digital to analog converter). ADCs (analog-to-digital converters), regular WAV files, and CDs are also hard-limited to 0dB.

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