Introduction to Audio Measurement
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.
This articles introduces the concept of non-linear distortion in audio and the pros and cons of the various methods for its measurement.
Loudspeakers can be tested anechoically, in a room and even out of doors. These various methods are discussed in detail here.
Wow and Flutter Measurement
Wow and flutter are caused by speed variations on tape (or vinyl records). They are insignificant in digital audio.
This article introduces the concepts of noise measurements, the need for weighting, and the commonly used A-weighting and ITU-R 468 weighting.
Crosstalk (or leakage) can be between stereo channels or between mixer channels. A weighting curve devised by the IBA to quantify its audibility is presented here.
Environmental Noise Measurement
Environmental noise comes from traffic, aircraft, and pubs and clubs. Here some of the regulations and standards are outlined and discussed.
Rumble measurement is made on turntables for (vinyl) records, in order to assess the very low frequency vibrations originating from bearings and pulleys.
The ‘Alignment level’ in an audio signal chain or on an audio recording is an anchor point that represents a reasonable or typical level…
MS20 Distortion Residue Bar Chart
This revealing set of measurements, performed automatically by our MS20 test set, is explained in more detailed here.
Recording with Omnis
Advice on recording with omni-directional microphones is presented here.
Digital sampling and reconstruction, the basis of all digital audio and video, is explained in detail here.
Audio Facts and Fallacies
True vs ‘PMPO’ Power
‘Mean sinewave power’ is the more meaningful measure of power, not ‘RMS power’. The term PMPO, widely used in specifications is also 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 is misleading, as explained here.
Programme Levels & Headroom
Analysing Programme Levels
A look at the typical dynamic range capacity of each stage of a recording/broadcast chain brings some big surprises!
Headroom and Compression
Maintaining headroom in original recordings is important, as is careful use of compression to avoid compromising the quality of music productions and broadcasts.
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’.
Equal-loudness contours define how our ears respond differently to pure tones over the audible frequency range.
ITU-R 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.