iXBT Labs - Computer Hardware in Detail

Platform

Video

Multimedia

Mobile

Other

Standards describing power in phonics



Many of you may have thought a lot of what is the power specifies in the certificates of acoustic systems and sound-amplifying equipment. Unfortunately, there are not many clear articles on this subject on the Net.

International standards

RMS - Root Mean Squared of the power value limited by the established harmonic distortions.

Power is measured by a 1 KHz sinusoidal signal at 10% THD. It is calculated as a product of root-mean-square values of voltage and current at the equivalent quantity of heat created by direct current. It means that power is numerically equal to a square root of a product of mean voltage and current squared.

For a sinusoidal signal a root-mean-square value is V2 times less than an amplitude value (x 0.707). It is, however, a virtual value. A term "root-mean-square" can be applied to voltage or current, but not to power. Its analog is an effective value.

Now I will try to explain why this concept is not important for audio characteristics description. Root-mean-square power makes sense in electrical engineering. And does not concern necessary a sinusoid. In case of music signals loud sound are heard better, than weak ones. And it is amplitude values that affect ears stronger than root-mean-square ones. It means that volume is not equivalent to power. That's why root-mean-square values make sense only in an electric meter, and amplitude ones in music. As for FS, I should note that falls in FS are noticeable less than peaks. It means that loud sounds are more informative than low sounds, and an average value will tell little.

So, RMS standard is not the best attempt to describe audio system parameters since it doesn't reflect volume as a value.

In amplifiers and acoustic systems this parameter finds narrow application as well - an amplifier which gives out 10% of distortions on not the maximum power is not widely spread. Transistor amplifier distortions, for example, do not exceed one hundredth of a percent before the max power is reached, and after that they sharply go up (irregular mode). Many acoustic systems working for a long time with a such distortion level can fall out.

PMPO (Peak Music Power Output) means max reachable peak signal's value irrespective of distortions at the min time period (usually at 10 ms).

The parameter shouldn't be, though, taken seriously.

DIN 45500 is a complex of IEEE generally accepted standards which describes different sound-amplifying characteristics of the equipment by a more reliable way.

DIN POWER is a value received on a real load (for an amplifier) or power input (to AC) limited by harmonic distortions.

It is measured with applying of a 1 KHz signal to the device input during 10 minutes. Power in measured at 1 % THD.

There are other types of measuring, e.g. DIN MUSIC POWER, which describes power of a music signal. Usually DIN music is higher than the DIN value.

General terminology

Pink noise is a group of random signals with a uniform spectral density of distribution to frequencies, it decreases with the frequency rise with 3 dB decrease per octave in the whole measuring range, with the dependence of a middle level on a frequency in the form of 1/f. Pink noise has a constant (in time) energy on any part of the frequency band.

White noise is a group of random signals with a uniform and constant spectral density of distribution to frequencies. White noise carries equal energy on any frequency part of the band.

Octave. A music frequency band, correlation of the extreme frequencies of which is equal to 2.

Electric power. Power dissipated on ohmic equivalent resistance numerically equal to a nominal electric resistance on AC, with the voltage equal to that on the AC clamps. I.e. on the resistance emulating a real load in the same conditions.

Write a comment below. No registration needed!


Article navigation:



blog comments powered by Disqus

  Most Popular Reviews More    RSS  

AMD Phenom II X4 955, Phenom II X4 960T, Phenom II X6 1075T, and Intel Pentium G2120, Core i3-3220, Core i5-3330 Processors

Comparing old, cheap solutions from AMD with new, budget offerings from Intel.
February 1, 2013 · Processor Roundups

Inno3D GeForce GTX 670 iChill, Inno3D GeForce GTX 660 Ti Graphics Cards

A couple of mid-range adapters with original cooling systems.
January 30, 2013 · Video cards: NVIDIA GPUs

Creative Sound Blaster X-Fi Surround 5.1

An external X-Fi solution in tests.
September 9, 2008 · Sound Cards

AMD FX-8350 Processor

The first worthwhile Piledriver CPU.
September 11, 2012 · Processors: AMD

Consumed Power, Energy Consumption: Ivy Bridge vs. Sandy Bridge

Trying out the new method.
September 18, 2012 · Processors: Intel
  Latest Reviews More    RSS  

i3DSpeed, September 2013

Retested all graphics cards with the new drivers.
Oct 18, 2013 · 3Digests

i3DSpeed, August 2013

Added new benchmarks: BioShock Infinite and Metro: Last Light.
Sep 06, 2013 · 3Digests

i3DSpeed, July 2013

Added the test results of NVIDIA GeForce GTX 760 and AMD Radeon HD 7730.
Aug 05, 2013 · 3Digests

Gainward GeForce GTX 650 Ti BOOST 2GB Golden Sample Graphics Card

An excellent hybrid of GeForce GTX 650 Ti and GeForce GTX 660.
Jun 24, 2013 · Video cards: NVIDIA GPUs

i3DSpeed, May 2013

Added the test results of NVIDIA GeForce GTX 770/780.
Jun 03, 2013 · 3Digests
  Latest News More    RSS  

Platform  ·  Video  ·  Multimedia  ·  Mobile  ·  Other  ||  About us & Privacy policy  ·  Twitter  ·  Facebook


Copyright © Byrds Research & Publishing, Ltd., 1997–2011. All rights reserved.