Microphones grow more directional at higher frequencies, dulling captured reverberant sound.

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 which 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 Howard, Jamie Angus, coustics and Psychoacoustics, 2414

Categorization

• DEFINE: Explains microphone directivity versus frequency and why off-axis/reverberant pickup is high-frequency deficient.
• QUESTION: Is this frequency-dependent directivity the same property that governs ‘air’ loss in distant-miked recordings?