The proximity effect is a boost in the low-frequency (bass) response of a directional microphone that occurs when the sound source is relatively close to the microphone. The phenomenon begins when the source is about two feet away from the mic capsule and becomes more noticeable as the subject gets closer to the mic. Used properly, a singer can use the proximity effect as a means of adding fullness to a voice; however, the effect can also emphasize nondesireable low-frequency noises such as breath sounds and plosives – popping consonants – such as "p" and "b" sounds.