Please, Question About Loudness

[Guest nickko]

good afternoon to all,

please, i need to know some things about loudness and volume and what is the difference bettween those two.

i have noticed that some cd's with the same sound level of - 3 db's sounded louder than others that have the same sound level - 3 db's.

thanks.

[Retrosaurus Rex]

It's sounds like your meters are comparing peak volume, but your ears are hearing a difference in average volume...

[Prometheus]

good afternoon to all,

please, i need to know some things about loudness and volume and what is the difference bettween those two.

i have noticed that some cd's with the same sound level of - 3 db's sounded louder than others that have the same sound level - 3 db's.

thanks.

It would depend on how heavily compressed the tracks are... A signal that is heavily compressed and has peaks at -3 dB could sound considerably louder than a signal that is uncompressed or lightly compressed and peaks at 0 dB

[Rudi]

Im no expert but Im sure Prometheus has it right. Compression maximises volume by cutting peaks & so maximising quieter parts. Also, some engineers still shift track volumes around to the same end. For example, a piano intro may be loud, but when the rest of the band kick in, its volume is reduced to support vocals and balance with the other instruments better.

Im told that compression is why most tv adds sound louder than the programs. I used to think is was deliberate.

[john]

actually it is deliberate... they compress heavily to achieve a very deliberate increase in volume and loudness.

Volume is definitive, but loudness depends on perception. in essence with a pure tone signal of -3 dB at 100 Hz will be perceived as 1000 times quieter than a pure tone signal of -3dB at 3kHz. This is because the human ear does not respond in a linear way to sound frequency... in other words our ears hear some frequencies better than others. In fact we don't really hear above 20kHz even when young... but the sound is still there, afterall dogs hear dog whistles don't they?

The reason why compression makes tracks sound louder is that compression works across the entire volume spectrum (within circuitry restraints) meaning that at any point in time the difference between the highest volume and the lowest volume is reduced. In turn that means that more of the frequencies making up the sound are closer to the peak volume than they once were.

Imagine you had 20000 speakers, each able to project a single frequency in Hz ranging from 1Hz to 20 kHz at a volume of -3 dBv (With respect to a reference voltage).. starting with one single speaker, turning each on one at a time... the volume is still -3 dB... but the perceived loudness will increase as each speaker is turned on.

So to sum up, the perceived loudness of a piece of music depends on the frequency content of the music, how close each frequency is to the peak volume and where the frequencies are in relation to the frequency sensitivity of the human ear.

Lastly, you can get compressors that can be tuned according to frequency... ie the amount of compression and boost applied depends on the frequency of the signal it is applied too. These don't tend to be cheap and there are far fewer on the market.

Hope that helps.