PlanetZ forums - scopeusers.com

Hi,

I've been on another forum where the topic of conversation was RMS levels for mastering purposes. It wasn't my thread so I didn't want to but in so I thought I'd come here to ask what are RMS levels? - What does it stand for? - What does it mean?

I'm not mastering anything yet and maybe I never will but it would be good to understand this RMS thingie...Thanks in advance...

It stands for Root Mean Square and is some kind average measurement.

Thus RMS requires a time-frame.

Vinco illustrates this perfectly by the peak/rms setting. RMS could thus mean average amplitude of peaks within a given time-frame. RMS is also "louder".

http://www.hifi-writer.com/he/misc/rmspower.htm

Oh no, another nit pick article! Whether it is correct or not it has been adopted by just about everyone to mean continuous average power delivered. Sometimes erroneously also referred to as "true power".
In the analog studio world, analog meters do not react as quickly to transients as digital peak meters hence they tend to display an average of the peaks and troughs (hence "RMS").
Take a mix with an RMS of say -8db. The average level of the signal, with reference to 0db, is -8db. If you are looking at your peak meters it will be spending most of it's time hovering around the -8db mark. That is going to be a pretty loud mix! The -8db should be -8dbFSD (Full Scale Deflection at 0db in digital land).

Out of interest, ever seen the PMPO rating on flashy bookshelf speaker systems? You know those systems that say 1000W PMPO!!!!!! It is a useless, meaningless over inflated rating. It basically means that with heaps of distortion and everything turned up the device may be capable of throwing a "peak" of 1000W at a fraction of a thousandth of a second in absolutely perfect conditions while the device is operating at 100% efficiency. In other words it will never get there and is pure sales rubbish! The RMS rating of the same device is probably around 50WRMS that the device can sustain for longer periods of time with only a small amount of distortion.

From Wikipedia:

"It is possible to calculate the RMS power of a signal. By analogy with RMS voltage and RMS current, RMS power is the square root of the mean of the square of the power over some specified time period. This quantity, which would be expressed in units of watts (RMS), has no physical significance and no practical use. However, the term "RMS power" is sometimes used in the consumer audio industry as an incorrect synonym for "mean power" or "average power". For a discussion of audio power measurements and their shortcomings, see Audio power."

bassdude is right

most audio editors will measure the RMS for a wave file, I have no idea of the maths/algorithms used to do this, but its a very useful measure related to apparent loudness

when mastering I usually aim for an RMS of around -11, which I find makes my songs loud enough, but not overly squashed

Well that's a start anyway. Thanks for the replies. I suppose I'll come across more jargon when I'm mastering something or trying to...