Exploring comb filtering effects in the recording studio: A lesson on room acoustics

Abstract

A common practice during a live music-recording session is to position microphones, so-called, “room mics” to capture the ambient characteristics of the recording space. An in-class, hands-on experiment was conducted at Belmont University’s Historic Columbia Studio A in order to measure and observe the effect of comb filtering on the signal captured by an on-axis room microphone placed at various heights from the floor. A total of seven positions were recorded, spanning from just above the floor to twelve feet in the air. Sine sweep measurements and musical samples from a live virtual jazz-quartet were taken at each position. Students were then asked to listen back and discuss their preferences for each microphone height, comparing their observations to the matching frequency response analysis. A majority of students enjoyed the recording with the microphone positioned at the floor corresponding with the least amount of comb filtering. Although listener preference data was not collected, this experiment demonstrated the use of interdisciplinary examples as an educational tool in the field of acoustics.