The proximity effect is easy to hear and demonstrate but very difficult to describe how it happens! The proximity effect is when the bass of directional (cardioid and hypercardioid) microphones is increased the closer the beatboxer gets to the microphone. This bass boost 'fattens' up the sound. It's all to do with how directional microphones are designed, phase and sound pressure levels. Note: It ONLY happens with directional microphones such as the Shure SM58.