Copyright © American Speech-Language-Hearing Association From: Guidelines for Selecting Microphones for Human Voice Production Research Am J Speech Lang Pathol. 2010;19(4):356-368. doi:10.1044/1058-0360(2010/09-0091) Legend: Speech signal recorded at 30 cm simultaneously with an omnidirectional and directional (cardioid) microphone in the presence of an ambient noise. The cardioid microphone lowers the effect of the ambient noise, as demonstrated in its cleaner spectrogram and lower SPLs during the speech pauses. (*In a strict sense, the signal from the cardiod microphone is not proportional to the sound pressure actually present in the room but rather approximates the pressure as it would have occurred in a less noisy environment.) Date of download: 10/14/2017 Copyright © American Speech-Language-Hearing Association