Directional microphones and speech
Reviewed by Joanna Lemanska

This study aimed to research how speech recognition, listening effort and localisation depends on hearing aids’ microphone configuration in people with moderate to severe hearing losses. Eighteen participants with sensorineural, symmetrical, moderate to severe hearing loss were tested. Participants were fitted bilaterally with the same type of hearing aids. Three microphone configurations were used, bilateral directional microphones, asymmetrical directional microphones and omnidirectional. Speech recognition was tested using the Connected Speech test with the background noise presented from four fixed directions and speech presented at 0° with a fixed sound pressure level. The background noise level was chosen from three possible values in a way which gives approximately 50% performance when omnidirectional microphones were used. Two tasks were used to assess listening effort, monosyllable word recognition and word categorisation (deciding as quickly as possible if a particular word can be used as a noun). The listening effort was measured using the same background noises. Localisation was evaluated using Spatial Test Requiring Effortful Speech Recognition (STRESR). For this investigation the speech was presented from one of four directions different from the noise directions. Three outcomes were evaluated, word recall, localisation accuracy and how quickly participants were able to identify the direction of the speech correctly. Results of this study showed that using the directional microphones improves speech recognition regardless of whether one or two directional microphones are used. Similarly, the listening effort improved when directional microphones were used. These findings are generally in accordance with previous studies. Surprisingly, the microphone configuration had no significant effect on the localisation task results which, as authors mentioned, may be caused by using a different methodical condition. Generally, this study confirmed again the usefulness of directional microphones. It would be interesting to research a larger population with different types of hearing losses.

How directional microphones affect speech recognition, listening effort and localisation for listeners with moderate-to-severe hearing loss.
Picou EM, Ricketts TA.
INTERNATIONAL JOURNAL OF AUDIOLOGY
2017;56(12):909-18.