Boundary layer microphones are popular as room microphones, with hemispherical pickup patterns that are highly constant throughout the frequency range. The boundary layer effect causes direct sound to be picked up with 3 dB greater sensitivity relative to the diffuse signal. This gives the microphone greater "reach" than a free-standing omni. In addition they avoid reflections from the floor, wall or ceiling on which they are placed, which could produce comb filter effects. This type of microphone is also suitable for use on conference tables.