I Need Help With dB 'Calculations'

Hi all! How would one calculate the overall change in volume when changing the individual volumes on an equalizer?

 

only those frequencies that you adjust will sound louder. the peak volume you hear will be the peak of the loudest frequency whether boosted or not. if you want any accuracy you have to measure your system's response before and after EQ.

Loudness volume doubling sound level change factor of perceived loudness decibel scale log compare intensities formula calculate power level noise levels volume logarithm dependence three four fold loudness sound - by what factor does level decrease dependence comparison decibel levels 3 dBSPL 6 dB 10 db double voltage sound pressure audio sound intensity acoustic power formula relationship decibels dB twice as loud two times double distance half level dependence auditory loudness formula sound noise loudness sound pressure intensity a-weighted twice as loud increase decrease SPL - sengpielaudio Sengpiel Berlin

 

If you are doing it in the digital realm, you need to reduce the overall gain by the same amount as the highest emphasis you have added. Not doing that risks digital overload in the downstream DAC. You might reduce the gain by an additional 2dB to 3dB as well, which will reduce the chances of intersample interpolation in many DACs causing an overage.

 

Wait a minute. Lets say I play a 300 Hz test tone at 80dB. Then I play an 80 dB 1000 Hz test tone. If I play both of them together, they sound equally loud as the individual tone?

 

The contribution of the EQ on the overall perception of loudness will depend on the musical source material. For example, if you were playing Techmaster P.E.B - Bassgasm, then boosting a 60Hz slider will increase the apparent volume much more than if you were playing some Bach harpsichord concertos.

The ear's perception of volume is subjective - two people might not agree on what represents a "doubling" of the volume. Generally 6dB is seen as a doubling of musical power, although it actually is 4x the wattage to produce.

Played individually, they will seem to have different volumes. Your ear is more sensitive to 1000Hz and will find it louder and more irritating at loud volumes. Your speakers may have differing response curves or resonances that reproduce one louder than the other. Press play on either or both media files below to come to your own conclusion.

 

300hz video:

 

Another example why dB is hard to translate into perception. Let's say we have a test tone like your audiologist may administer, one that is the quietest sound level you can detect. If we reduce the volume by 6dB, it's not half as loud to you - you hear nothing.

 

Depends on the Equal Loudness Contours, as human auditory perception is not linear. You need some fancy equations and even then it's probably only a guess. Either match the levels before and after EQ by ear, or use a digital EQ such as the TDR SlickEQ, which has built in auto-loudness adjustment. I think that one uses an "intelligent" algorithm, probably based on the equal loudness contours, to deternine the amount of gain to apply. From the manual:

"This buttons turns the automatic EQ loudness compensation on and off. Activating this mode will prevent the operator’s decisions from being distracted by the 'louder is better' phenomenon."

Here are a couple of screen grabs to show what it does:

Only boosts with EQ Auto Gain OFF:


Same EQ with Auto Gain ON: