Audio Facts and Fallacies

True vs 'PMPO' Power 'Mean sinewave power' is the meaningful measure of power, not 'RMS power'. The term PMPO, widely used in specifications is meaningless and misleading.

Signal-Noise and Dynamic Range These are confusing terms for many reasons. The '96dB Dynamic Range' figure so often quoted for 16-bit audio has no proper basis, as explained here.

Digital Audio

Digital Sampling Digital sampling and reconstruction, the basis of all Digital Audio and Video, is widely misunderstood.

Introduction to Audio Measurement

Noise Measurement This article introduces the concepts of noise measurements, the need for weighting, and the commonly used A-weighting and ITU-R 468 weighting.

Understanding Decibels (dB) Basic explanation of the use of dB, with definitions of dBu dBFS dBm dBSPL and an explanation of why Lindos favours dB AL.

Distortion Measurement Non-linear distortion explained, and why the traditional method of measurement (THD) is unsatisfactory. The Distortion Residue method explained.

Rumble Measurement Rumble measurement is made on turntables for (vinyl) records, in order to assess the very low frequency vibrations originating from bearings and pulleys.

Wow & Flutter Measurement Wow and flutter are caused by speed variations on tape (or vinyl records). They are insignificant in digital audio.

Crosstalk measurement Crosstalk can be between stereo channels or between mixer channels. A weighting curve devised by the IBA is presented here.

Lindos Sequence Testing How Lindos Sequence testing works.

Loudspeaker measurement Loudspeakers can easily be tested out of doors, pointing at the sky, without any need for an anechoic chamber, to produce a 'half-space' response.

Environmental Noise Measurement Environmental noise comes from traffic, aircraft, and increasingly, pubs and clubs. Regulations and standards are currently confused and inadequate.

Making Measurements with the MiniSonic

Measurements in Detail

A-weighting in detail The derivation of the A-weighting curve, and its limitations, with a detailed history of 'equal loudness contours'.

468 - Weighting in Detail ITU-R 468 Weighting, formerly known as CCIR-468 weighting, is the preferred method for subjectively valid results that allow fair comparisons.

Equal-Loudness Contours Equal-loudness contours define how our ears respond differently to pure tones over the audible frequency range.

Programme Levels & Headroom

Analysing Programme Levels A real look at typical program levels brings some surprises!

Headroom and Compression Loss of headroom is suggested as the major factor compromising quality on CD's and broadcasts. 'Managed Headroom' is proposed as a better approach.

Alignment Level Referencing levels to maximum permitted level or full-scale leads to confusion and loss of quality. The concept of Alignment level, as recommended by the EBU, has many advantages.

UniSon