Editing Parabolic microphone (section)

==Limitations==
Parabolic microphones are generally not used for [[high-fidelity]] applications because dishes small enough to be portable have poor low-frequency response. This is because, from the [[Angular resolution#The_Rayleigh_criterion|Rayleigh criterion]], parabolic dishes can only focus waves with a wavelength much smaller than the diameter of their aperture. The wavelength of sound waves at the low end of human hearing (20&nbsp;Hz) is about {{convert|17|metres|feet}}; focusing them would require a dish much larger than this. A typical parabolic microphone dish with a diameter of one metre has little [[directivity]] for sound waves longer than 30&nbsp;cm, corresponding to frequencies below 1&nbsp;kHz. For higher frequencies, a gain of about 15&nbsp;[[decibel|dB]] can be expected. But when the wavelength of the sound becomes comparable with the diameter of the parabolic dish, the response falls away.<ref name=S&R>{{cite book|last1=Rumsey|first1=Francis|last2=McCormick|first2=Tim|title=Sound and Recording|url=https://archive.org/details/soundrecording00rums|url-access=limited|date=2009|publisher=Elsevler Ltd.|location=Burlington, MA |isbn=978-0-240-52163-3|page= 60|edition=6}}</ref>

A [[shotgun microphone]], or a [[phased array]] of microphones, may be used as an alternative for applications requiring directional selectivity with high fidelity.