| Audio Facts and Fallacies |
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'Mean sinewave power' is the meaningful measure of power, not 'RMS power'. The term PMPO, widely used in specifications is meaningless and misleading. |
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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. |
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| Digital Audio |
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Digital sampling and reconstruction, the basis of all Digital Audio and Video, is widely misunderstood. |
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| Introduction to Audio Measurement |
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This article introduces the concepts of noise measurements, the need for weighting, and the commonly used A-weighting and ITU-R 468 weighting. |
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Basic explanation of the use of dB, with definitions of dBu dBFS dBm dBSPL and an explanation of why Lindos favours dB AL. |
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Non-linear distortion explained, and why the traditional method of measurement (THD) is unsatisfactory. The Distortion Residue method explained. |
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Rumble measurement is made on turntables for (vinyl) records, in order to assess the very low frequency vibrations originating from bearings and pulleys. |
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Wow and flutter are caused by speed variations on tape (or vinyl records). They are insignificant in digital audio. |
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Crosstalk can be between stereo channels or between mixer channels. A weighting curve devised by the IBA is presented here. |
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How Lindos Sequence testing works. |
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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. |
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Environmental noise comes from traffic, aircraft, and increasingly, pubs and clubs. Regulations and standards are currently confused and inadequate. |
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| Making Measurements with the MiniSonic |
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The distortion residue bar chart. |
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| Measurements in Detail |
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The derivation of the A-weighting curve, and its limitations, with a detailed history of 'equal loudness contours'. |
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ITU-R 468 Weighting, formerly known as CCIR-468 weighting, is the preferred method for subjectively valid results that allow fair comparisons. |
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Equal-loudness contours define how our ears respond differently to pure tones over the audible frequency range. |
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| Programme Levels & Headroom |
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A real look at typical program levels brings some surprises! |
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Loss of headroom is suggested as the major factor compromising quality on CD's and broadcasts. 'Managed Headroom' is proposed as a better approach. |
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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. |
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| UniSon |
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No proper standards exist for analog audio interfacing. UniSon is a proposed standard to guarantee proper interworking between equipment. |
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