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NIST System for Measuring the Directivity Index of Hearing Aids under Simulated Real-Ear Conditions.

Wagner RP - J Res Natl Inst Stand Technol (2013)

Bottom Line: The capabilities of the system were demonstrated over the frequency range of one-third-octave bands with center frequencies from 200 Hz to 8000 Hz through NIST participation in an interlaboratory comparison.Directivity measurements were made for a total of six programmed memories in two different hearing aids and for the unaided manikin with the manikin right pinna accompanying the aids.Omnidirectional, cardioid, and bidirectional response patterns were measured.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8223.

ABSTRACT
The directivity index is a parameter that is commonly used to characterize the performance of directional hearing aids, and is determined from the measured directional response. Since this response is different for a hearing aid worn on a person as compared to when it is in a free field, directivity index measurements of hearing aids are usually done under simulated real-ear conditions. Details are provided regarding the NIST system for measuring the hearing aid directivity index under these conditions and how this system is used to implement a standardized procedure for performing such measurements. This procedure involves a sampling method that utilizes sound source locations distributed in a semi-aligned zone array on an imaginary spherical surface surrounding a standardized acoustical test manikin. The capabilities of the system were demonstrated over the frequency range of one-third-octave bands with center frequencies from 200 Hz to 8000 Hz through NIST participation in an interlaboratory comparison. This comparison was conducted between eight different laboratories of members of Working Group S3/WG48, Hearing Aids, established by Accredited Standards Committee S3, Bioacoustics, which is administered by the Acoustical Society of America and accredited by the American National Standards Institute. Directivity measurements were made for a total of six programmed memories in two different hearing aids and for the unaided manikin with the manikin right pinna accompanying the aids. Omnidirectional, cardioid, and bidirectional response patterns were measured. Results are presented comparing the NIST data with the reference values calculated from the data reported by all participating laboratories.

No MeSH data available.


Related in: MedlinePlus

Photograph of the measurement system setup in the NIST large anechoic chamber. Hearing aids are tested in place on the manikin, which is mounted on a turntable that rotates the manikin in the horizontal plane to adjust the azimuth angle. Adjustment of the elevation angle is done with a vertical positioning system that moves a single loudspeaker on the path of a circular arc. A weight and pulley system elevates the loudspeaker, which is fixed at a given elevation angle by a thin steel stay wire.
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f2-jres.118.005: Photograph of the measurement system setup in the NIST large anechoic chamber. Hearing aids are tested in place on the manikin, which is mounted on a turntable that rotates the manikin in the horizontal plane to adjust the azimuth angle. Adjustment of the elevation angle is done with a vertical positioning system that moves a single loudspeaker on the path of a circular arc. A weight and pulley system elevates the loudspeaker, which is fixed at a given elevation angle by a thin steel stay wire.

Mentions: Measurements are done in the NIST large anechoic chamber, which has acoustical properties that have been investigated and reported elsewhere [17]. The chamber free field dimensions, measured wedge tip to wedge tip, are 6.7 m by 10.0 m by 6.7 m. All interior surfaces of the chamber are covered with sound-absorptive wedge modules 1.8 m long that have a cutoff frequency of 45 Hz [18]. Figure 2 is a photograph of the measurement system setup in the anechoic chamber. A Knowles Electronics Manikin for Acoustics Research (KEMAR)1 [19], which meets the applicable specifications for standardized acoustical test manikins [13,14], is used with one neck ring in place and no clothing or wig. A standardized occluded-ear simulator [20] is used with the large pinnae supplied for KEMAR. Hearing aids are tested in/on the right ear of the manikin, which is mounted on a turntable that rotates the manikin in the horizontal plane to adjust the azimuth angle. The axis of rotation of the manikin passes through the reference point of the manikin. The manikin-turntable combination sits on a wooden support that is placed in the center of the steel wire mesh floor that spans the middle of the anechoic chamber. Both the turntable and the support are covered in fiberglass to absorb incident sound.


NIST System for Measuring the Directivity Index of Hearing Aids under Simulated Real-Ear Conditions.

Wagner RP - J Res Natl Inst Stand Technol (2013)

Photograph of the measurement system setup in the NIST large anechoic chamber. Hearing aids are tested in place on the manikin, which is mounted on a turntable that rotates the manikin in the horizontal plane to adjust the azimuth angle. Adjustment of the elevation angle is done with a vertical positioning system that moves a single loudspeaker on the path of a circular arc. A weight and pulley system elevates the loudspeaker, which is fixed at a given elevation angle by a thin steel stay wire.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487306&req=5

f2-jres.118.005: Photograph of the measurement system setup in the NIST large anechoic chamber. Hearing aids are tested in place on the manikin, which is mounted on a turntable that rotates the manikin in the horizontal plane to adjust the azimuth angle. Adjustment of the elevation angle is done with a vertical positioning system that moves a single loudspeaker on the path of a circular arc. A weight and pulley system elevates the loudspeaker, which is fixed at a given elevation angle by a thin steel stay wire.
Mentions: Measurements are done in the NIST large anechoic chamber, which has acoustical properties that have been investigated and reported elsewhere [17]. The chamber free field dimensions, measured wedge tip to wedge tip, are 6.7 m by 10.0 m by 6.7 m. All interior surfaces of the chamber are covered with sound-absorptive wedge modules 1.8 m long that have a cutoff frequency of 45 Hz [18]. Figure 2 is a photograph of the measurement system setup in the anechoic chamber. A Knowles Electronics Manikin for Acoustics Research (KEMAR)1 [19], which meets the applicable specifications for standardized acoustical test manikins [13,14], is used with one neck ring in place and no clothing or wig. A standardized occluded-ear simulator [20] is used with the large pinnae supplied for KEMAR. Hearing aids are tested in/on the right ear of the manikin, which is mounted on a turntable that rotates the manikin in the horizontal plane to adjust the azimuth angle. The axis of rotation of the manikin passes through the reference point of the manikin. The manikin-turntable combination sits on a wooden support that is placed in the center of the steel wire mesh floor that spans the middle of the anechoic chamber. Both the turntable and the support are covered in fiberglass to absorb incident sound.

Bottom Line: The capabilities of the system were demonstrated over the frequency range of one-third-octave bands with center frequencies from 200 Hz to 8000 Hz through NIST participation in an interlaboratory comparison.Directivity measurements were made for a total of six programmed memories in two different hearing aids and for the unaided manikin with the manikin right pinna accompanying the aids.Omnidirectional, cardioid, and bidirectional response patterns were measured.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-8223.

ABSTRACT
The directivity index is a parameter that is commonly used to characterize the performance of directional hearing aids, and is determined from the measured directional response. Since this response is different for a hearing aid worn on a person as compared to when it is in a free field, directivity index measurements of hearing aids are usually done under simulated real-ear conditions. Details are provided regarding the NIST system for measuring the hearing aid directivity index under these conditions and how this system is used to implement a standardized procedure for performing such measurements. This procedure involves a sampling method that utilizes sound source locations distributed in a semi-aligned zone array on an imaginary spherical surface surrounding a standardized acoustical test manikin. The capabilities of the system were demonstrated over the frequency range of one-third-octave bands with center frequencies from 200 Hz to 8000 Hz through NIST participation in an interlaboratory comparison. This comparison was conducted between eight different laboratories of members of Working Group S3/WG48, Hearing Aids, established by Accredited Standards Committee S3, Bioacoustics, which is administered by the Acoustical Society of America and accredited by the American National Standards Institute. Directivity measurements were made for a total of six programmed memories in two different hearing aids and for the unaided manikin with the manikin right pinna accompanying the aids. Omnidirectional, cardioid, and bidirectional response patterns were measured. Results are presented comparing the NIST data with the reference values calculated from the data reported by all participating laboratories.

No MeSH data available.


Related in: MedlinePlus