In the near field, near-field acoustic holography (NAH) helps analyze impulsive door slams. In this case, a device is used that closes the door repeatedly at constant speed. The transient phenomenon becomes a repeatable transient. An array is then placed in the near field. This array has a microphone spacing of 8cm, resulting in a 216cm by 48cm hologram. This limits the maximum frequency to 2140Hz. The hologram in figure 2 shows the sound source of the door slam at 512Hz. NAH is best suited for this analysis. It offers the required spatial resolution at the low frequency of 512Hz.
Figure 2: Door slam with NAH More information on:
