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The effect of hearing aid microphone mode on performance in an auditory orienting task.

Brimijoin WO, Whitmer WM, McShefferty D, Akeroyd MA - Ear Hear (2014 Sep-Oct)

Bottom Line: Although directional microphones on a hearing aid provide a signal-to-noise ratio benefit in a noisy background, the amount of benefit is dependent on how close the signal of interest is to the front of the user.The authors hypothesized that listeners using directional microphones would have greater difficulty in rapidly and accurately orienting to off-axis signals than they would when using omnidirectional microphones.If hearing-aid users are to receive maximum directional benefit in noisy environments, both adaptive directionality in hearing aids and clinical advice on using directional microphones should take head movement and orientation behavior into account.

View Article: PubMed Central - PubMed

Affiliation: MRC Institute of Hearing Research (Scottish Section), Glasgow Royal Infirmary, Glasgow, Lanarkshire, United Kingdom.

ABSTRACT

Objectives: Although directional microphones on a hearing aid provide a signal-to-noise ratio benefit in a noisy background, the amount of benefit is dependent on how close the signal of interest is to the front of the user. It is assumed that when the signal of interest is off-axis, users can reorient themselves to the signal to make use of the directional microphones to improve signal-to-noise ratio. The present study tested this assumption by measuring the head-orienting behavior of bilaterally fit hearing-impaired individuals with their microphones set to omnidirectional and directional modes. The authors hypothesized that listeners using directional microphones would have greater difficulty in rapidly and accurately orienting to off-axis signals than they would when using omnidirectional microphones.

Design: The authors instructed hearing-impaired individuals to turn and face a female talker in simultaneous surrounding male-talker babble. Participants pressed a button when they felt they were accurately oriented in the direction of the female talker. Participants completed three blocks of trials with their hearing aids in omnidirectional mode and three blocks in directional mode, with mode order randomized. Using a Vicon motion tracking system, the authors measured head position and computed fixation error, fixation latency, trajectory complexity, and proportion of misorientations.

Results: Results showed that for larger off-axis target angles, listeners using directional microphones took longer to reach their targets than they did when using omnidirectional microphones, although they were just as accurate. They also used more complex movements and frequently made initial turns in the wrong direction. For smaller off-axis target angles, this pattern was reversed, and listeners using directional microphones oriented more quickly and smoothly to the targets than when using omnidirectional microphones.

Conclusions: The authors argue that an increase in movement complexity indicates a switch from a simple orienting movement to a search behavior. For the most off-axis target angles, listeners using directional microphones appear to not know which direction to turn, so they pick a direction at random and simply rotate their heads until the signal becomes more audible. The changes in fixation latency and head orientation trajectories suggest that the decrease in off-axis audibility is a primary concern in the use of directional microphones, and listeners could experience a loss of initial target speech while turning toward a new signal of interest. If hearing-aid users are to receive maximum directional benefit in noisy environments, both adaptive directionality in hearing aids and clinical advice on using directional microphones should take head movement and orientation behavior into account.

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Trajectory complexity as a function of target angle for low In-Situ Directivity Index (ISDI) listeners (A) and high ISDI listeners (B). Only the high ISDI group showed an increase in complexity as a function of target angle and only in directional mode (closed squares), not in omnidirectional mode (open circles).
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Figure 6: Trajectory complexity as a function of target angle for low In-Situ Directivity Index (ISDI) listeners (A) and high ISDI listeners (B). Only the high ISDI group showed an increase in complexity as a function of target angle and only in directional mode (closed squares), not in omnidirectional mode (open circles).

Mentions: Figure 6 shows trajectory complexity as a function of target angle. For trajectory complexity in low-ISDI listeners (Fig. 6A), we found no effect of microphone mode or target angle, nor did we find a significant interaction effect between the two. This suggests that low-ISDI listeners oriented smoothly and consistently toward a target regardless of the mode of their hearing aids or the off-axis angle of the target sound.


The effect of hearing aid microphone mode on performance in an auditory orienting task.

Brimijoin WO, Whitmer WM, McShefferty D, Akeroyd MA - Ear Hear (2014 Sep-Oct)

Trajectory complexity as a function of target angle for low In-Situ Directivity Index (ISDI) listeners (A) and high ISDI listeners (B). Only the high ISDI group showed an increase in complexity as a function of target angle and only in directional mode (closed squares), not in omnidirectional mode (open circles).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4232295&req=5

Figure 6: Trajectory complexity as a function of target angle for low In-Situ Directivity Index (ISDI) listeners (A) and high ISDI listeners (B). Only the high ISDI group showed an increase in complexity as a function of target angle and only in directional mode (closed squares), not in omnidirectional mode (open circles).
Mentions: Figure 6 shows trajectory complexity as a function of target angle. For trajectory complexity in low-ISDI listeners (Fig. 6A), we found no effect of microphone mode or target angle, nor did we find a significant interaction effect between the two. This suggests that low-ISDI listeners oriented smoothly and consistently toward a target regardless of the mode of their hearing aids or the off-axis angle of the target sound.

Bottom Line: Although directional microphones on a hearing aid provide a signal-to-noise ratio benefit in a noisy background, the amount of benefit is dependent on how close the signal of interest is to the front of the user.The authors hypothesized that listeners using directional microphones would have greater difficulty in rapidly and accurately orienting to off-axis signals than they would when using omnidirectional microphones.If hearing-aid users are to receive maximum directional benefit in noisy environments, both adaptive directionality in hearing aids and clinical advice on using directional microphones should take head movement and orientation behavior into account.

View Article: PubMed Central - PubMed

Affiliation: MRC Institute of Hearing Research (Scottish Section), Glasgow Royal Infirmary, Glasgow, Lanarkshire, United Kingdom.

ABSTRACT

Objectives: Although directional microphones on a hearing aid provide a signal-to-noise ratio benefit in a noisy background, the amount of benefit is dependent on how close the signal of interest is to the front of the user. It is assumed that when the signal of interest is off-axis, users can reorient themselves to the signal to make use of the directional microphones to improve signal-to-noise ratio. The present study tested this assumption by measuring the head-orienting behavior of bilaterally fit hearing-impaired individuals with their microphones set to omnidirectional and directional modes. The authors hypothesized that listeners using directional microphones would have greater difficulty in rapidly and accurately orienting to off-axis signals than they would when using omnidirectional microphones.

Design: The authors instructed hearing-impaired individuals to turn and face a female talker in simultaneous surrounding male-talker babble. Participants pressed a button when they felt they were accurately oriented in the direction of the female talker. Participants completed three blocks of trials with their hearing aids in omnidirectional mode and three blocks in directional mode, with mode order randomized. Using a Vicon motion tracking system, the authors measured head position and computed fixation error, fixation latency, trajectory complexity, and proportion of misorientations.

Results: Results showed that for larger off-axis target angles, listeners using directional microphones took longer to reach their targets than they did when using omnidirectional microphones, although they were just as accurate. They also used more complex movements and frequently made initial turns in the wrong direction. For smaller off-axis target angles, this pattern was reversed, and listeners using directional microphones oriented more quickly and smoothly to the targets than when using omnidirectional microphones.

Conclusions: The authors argue that an increase in movement complexity indicates a switch from a simple orienting movement to a search behavior. For the most off-axis target angles, listeners using directional microphones appear to not know which direction to turn, so they pick a direction at random and simply rotate their heads until the signal becomes more audible. The changes in fixation latency and head orientation trajectories suggest that the decrease in off-axis audibility is a primary concern in the use of directional microphones, and listeners could experience a loss of initial target speech while turning toward a new signal of interest. If hearing-aid users are to receive maximum directional benefit in noisy environments, both adaptive directionality in hearing aids and clinical advice on using directional microphones should take head movement and orientation behavior into account.

Show MeSH
Related in: MedlinePlus