Microphones and sound source

According to ISO 140-4:1997 the following are minimum separating distances:

•      0,7 m between microphone positions

•      0,7 m between loudspeaker positions

•      0,5 m between any microphone position and room boundaries or diffusers

•      0,5 m between any loudspeaker position and room boundaries (small irregularities of the room boundaries can be ignored)

•      Different loudspeaker positions should not be located in parallel to the room boundaries

•      1,0 m between any microphone position and the sound source

A minimum of five fixed microphone positions shall be used. They shall be evenly distributed within the space permitted for measurement in the room.

This method is based on using a single sound source. In this case at least two sound source positions must be used.

The loudspeaker should be positioned to give an as diffuse sound field as possible and as far away from the flanking elements influencing the sound transmission so that the direct radiation is not dominant.

Note: For small rooms you may place the loudspeaker in the corner of the source room. But note that this may influence the flanking transmission and may give an increase of level fluctuations in the source room.