Shilling a laser spotlight on the egg box myth

摘要

Egg boxes have often been suggested as a cheap acoustic treatment for the home studio. In March 1988 the Riverbank Acoustical Laboratories measured the absorption properties of egg boxes, finding that their noise reduction index was 0.4. The results showed that at low frequencies egg boxes did very little but from 700 Hz up there were some moderate levels of absorption. This experiment deals with the question of whether they can be used as absorbers but what about their diffusion characteristics? This article will use the example of measuring the spatial distribution of reflections from a panel covered with egg boxes to show how the non-invasive technique of refracto-vibrometry can be used to measure a sound field.