Recently we’ve been looking into the subject of acoustic holography. With this technique, a set of acoustic measurements made in one area of an acoustic field can be used to derive values elsewhere.
For example, by measuring pressure with a rectangular array of microphones in front of a loudspeaker, the pressure on the surface of the loudspeaker can be derived. As you can imagine it is not easy to measure pressure directly on the surface with good accuracy. But once you have pressure on the surface of the loudspeaker, modeling techniques then allow acoustic quantities, such as intensity, to be calculated everywhere external to and on the structure. It’s basically a relatively convenient way of getting a very clear and detailed picture of a radiated acoustic field, which obviously is of interest to us at B&W.
That’s the theory at least and I’m side-stepping some very complex mathematical and experimental problems. We have a project assessing the feasibility of applying this technique to loudspeakers. The good news for us is that the mathematics used is similar to that used for computer simulation techniques that are already very familiar with – we have been using and writing computer simulation programs for 30 years.