Low frequencies radiate omnidirectionally while high frequencies become directional

Evidence

Most practical microphones do not have an even response at all angles as a function of frequency. In general, they become more directional as the frequency increases. As most microphones are designed to give a specified on-axis frequency response in order to capture the direct sound accurately, this results in a response to the reverberant sound that falls with frequency. For recording contexts in which the direct sound dominates, for example close miking, this effect is not important. However, in recordings in which the reverberant field dominates, for example classical music recording, the effect is significant. Applying some high-frequency boost to the microphone signal can compensate for this. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2430 (#exemplifies, via linked claim)

Categorization

• XREF: connects to: Shorter wavelengths scatter more strongly from small objects than longer ones do.; Short wavelengths escape open pipe ends while long wavelengths reflect back; Stringed instruments radiate low frequencies omnidirectionally but high frequencies directionally (+4 more)

Broader Connections

• Higher frequencies focus sound into a narrowing forward beam #corroborates (0.95)
• Microphones become more directional at higher frequencies, darkening off-axis reverberant sound #exemplifies (0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2430
• Small vibrating objects radiate weak sound because source size is far under one wavelength #corroborates (0.75)
• Flat surfaces reflect low-frequency sound specularly but scatter high-frequency sound #expands (0.72)