Is there such a thing as a unidirectional microphone?

Question: Is there such a thing as a 'unidirectional microphone' (a microphone that is sensitive in one direction only)?

Although the term is quite widely used, particularly by audio equipment dealers, there is no such thing as a unidirectional microphone outside of very specialized applications other than music.

Normally, the term 'unidirectional microphone' is used in respect of the cardioid pattern mic. This mic is most sensitive at the front, still very sensitive at the sides, only 6 dB down in level 120 degrees around, and only insensitive to sounds arriving from the rear. In other words, it is only insensitive in one direction, rather than only being sensitive in one direction.

So if you point a cardioid mic at a trombone player in a band, it will also clearly pick up the trumpet player at the side.

The most highly directional microphones are the interference tube (sometimes known as the 'shotgun' or 'rifle' mic) and the parabolic reflector mic. Interference tube mics are widely used in TV and film sound recording, but their sound quality is compromised and they are not usually considered adequate for music. Their better directionality does not compensate for the drop-off in quality.

Parabolic reflector mics are used in sports broadcasting to pick up comments from the players on the field. They are impressively directional, but the sound quality is definitely not up to the standard required for music recording.