Proximity Effect is a boost in the upper bass frequencies that increases with the closeness (proximity) of the sound source. Microphones with cardioid and bi-directional polar patterns exhibit this effect much more than omnidirectional microphones. Proximity effect can be used to add fullness to a track, such as vocals, where a few inches on or off the microphone can make a big difference. Proximity effect can also cause unwanted boominess, for example, on acoustic guitar, so proper mic positioning is important. Placing the microphone too close to the instrument, especially the sound hole, will result in an overly bassy sound. Many engineers find the sweet spot to be 9-12″ off the twelfth fret or where the neck meets the body. Much of today’s modern rock takes advantage of proximity effect when miking guitar amplifiers by putting a dynamic mic and/or a ribbon mic right up on the cone of the speaker, creating a ‘larger than life’ sound.