Recorders	Microphones/Transducers	Bat detectors	Shock-mounts
	CompactFlash	Overview	Playback	Cables
	Hard-drive	Shotgun	Headphones	Protective cases
	R-DAT	Parabolic reflector	Speakers	Additional
	MiniDisc	Omni-directional	Amplifiers	Helpful Reads
	Analog	Uni-directional	Accessories	Vendors
		Infrasonic	Preamps	Inquiries
		Hydrophones

Uni-directional microphones (commonly known as cardioids or hyper-cardioids) feature a directional pickup pattern. This means that the device is most sensitive towards the front of the microphone, slightly less off to the sides, and has the least sensitivity from the back of the unit. This directivity can be used to one's advantage. For example, by positioning the backside of a cardioid microphone towards an unwanted noise source one can significantly reduce the level of the offending noise relative to the sound of interest. This feature can often help when recording in indoor locations such as aviaries, research cages, and observation booths. A pair of cardioid microphones can also be used to do stereo environmental recording where directionality is required.

The Sennheiser K6/ME-64 ($380) cardioid modular microphone system is a relatively low-cost option. This is especially true if one already owns a K6 power module from the Sennheiser modular shotgun system. An accessory windscreen MZW-64 is recommended.

The high-end cardioid microphone is the Sennheiser MKH-40 that sells for about $1,170. Just like other members of the MKH series, the MKH-40 is almost totally immune to high humidity related problems. They also exhibit extremely low self-noise, and offer very flat frequency response over the usable bandwidth. Their high sensitivity will require special shock-mounting and wind protection to make them suitable for handheld field use. 48-volt phantom powering is required.