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Review
. 2005;9(4):199-226.
doi: 10.1177/108471380500900404.

Clinical protocols for hearing instrument fitting in the Desired Sensation Level method

Marlene Bagatto  1 , Sheila Moodie, Susan Scollie, Richard Seewald, Shane Moodie, John Pumford, K P Rachel Liu
Affiliations
Review

Clinical protocols for hearing instrument fitting in the Desired Sensation Level method

Marlene Bagatto et al. Trends Amplif. 2005.

Abstract

A discussion of the protocols used particularly in the clinical application of the Desired Sensation Level (DSL) Method is presented in this chapter. In the first section, the measurement and application of acoustic transforms is described in terms of their importance in the assessment phase of the amplification fitting process. Specifically, the implications of individual ear canal acoustics and their impact on accurately defining hearing thresholds are discussed. Detailed information about the statistical strength of the real-ear-to-coupler difference (RECD) measurement and how to obtain the measure in young infants is also provided. In addition, the findings of a study that examined the relationship between behavioral and electrophysiologic thresholds in real-ear SPL is described. The second section presents information related to the electroacoustic verification of hearing instruments. The RECD is discussed in relation to its application in simulated measurements of real-ear hearing instrument performance. In particular, the effects of the transducer and coupling method during the RECD measurement are described in terms of their impact on verification measures. The topics of insertion gain, test signals, and venting are also considered. The third section presents three summary tables that outline the hearing instrument fitting process for infants, children, and adults. Overall, this chapter provides both clinical and scientific information about procedures used in the assessment and verification stages of the DSL Method.

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Figures

Figure 1.
Figure 1.
Real-ear-to-coupler differences (RECD) (in dB) measured with (A and B) foam/immittance tips and (C and D) earmolds as a function of age at 500 and 4000 Hz (adapted from Bagatto et al., 2002).
Figure 2.
Figure 2.
Real-ear-to-coupler differences (RECD) (in dB) measured with (A) foam/immittance tips and (B) earmolds as a function of age at 3000 Hz. The sloping line indicates the linear regression represented by the prediction equation. The horizontal line represents the mean RECD values for a particular age range.
Figure 3.
Figure 3.
Probe tube coupled to ER-10 3.5-mm otoacoustic emission tip using plastic film.
Figure 4.
Figure 4.
Comparison of derived behavioral and auditory brainstem response (ABR) thresholds in dB SPL for (A) 500 Hz, (B) 1000 Hz, (C) 2000 Hz and (D) 4000 Hz. Filled circles indicate data for hearing impaired subjects and open circles indicate data for subjects with normal hearing. The diagonal line represents perfect correspondence.
Figure 5.
Figure 5.
Schematic diagram of the transformation processes used to convert target values from sound pressure level in the ear canal to other formats commonly used in the electroacoustic evaluation of hearing instruments. RECD = real-ear-to-coupler difference; REAG = real-ear aided gain; REUG = real-ear unaided gain; REIG = real-ear insertion gain.
Figure 6.
Figure 6.
The mean difference between real-ear-to-coupler difference (RECD) values that were measured using the gold standard procedure (ER3A Insert Earphone [10 ohm]/HA2 2-cc coupler) and five other RECD measurement transducers as a function of frequency for 15 subjects. Panel A shows results when the custom earmold used has 35 mm of tubing. Panel B shows results when the custom earmold used has 45 mm of tubing. A value closer to 0 indicates little difference between the two measurement conditions was noted.
Figure 7.
Figure 7.
The relative difference values obtained for the ER3A/HA2 2-cc coupler real-ear-to-coupler difference (RECD) measurement procedure and the hearing instrument RECD measurement procedure as a function of frequency for 15 subjects. A positive value indicates that the RECD measured using the hearing instrument transducer generated a higher RECD value at that frequency than the ER3A/HA2 RECD measurement procedure.
Figure 8.
Figure 8.
The Desired Sensation Level (DSL) recommended protocol for hearing instrument fitting to infants. RECD = real-ear-to-coupler difference; DSL m[i/o] = Desired Sensation Level multistage input/output; nHL = normalized hearing level; eHL = estimated hearing level; BTE = behind-the-ear; REAR = real-ear aided response; RESR = real-ear saturation response.
Figure 9.
Figure 9.
The Desired Sensation Level (DSL) recommended protocol for hearing instrument fitting to children. RECD = real-ear-to-coupler difference; DSL m[i/o] = Desired Sensation Level multistage input/output; HL = hearing level; BTE = behind-the-ear; REAR = real-ear aided response; RESR = real-ear saturation response.
Figure 10.
Figure 10.
The Desired Sensation Level (DSL) recommended protocol for hearing instrument fitting to adults. RECD = real-ear-to-coupler difference; DSL m[i/o] = Desired Sensation Level multistage input/output; HL = hearing level; REAR = real-ear aided response; RESR = real-ear saturation response.
None
Auditory Brainstem Response Waveform Bracketing Procedure for Threshold Estimation Using Tone-Burst Stimuli
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References

    1. American Academy of Audiology (2003). Pediatric Amplification Protocol, Draft American Academy of Audiology.
    1. American National Standards Institute (1997). Methods of Measurement of Real-Ear Performance Characteristics of Hearing Aids. ANSI S3.46–1997. New York: Acoustical Society of America
    1. American National Standards Institute (1996). Specification for Audiometers. ANSI S3.6–1996. New York: Acoustical Society of America
    1. American Speech Language and Hearing Association (2004). Guidelines for the audiologic assessment of children from birth to 5 years of age. http://www.asha.org/members/deskref.journals/deskref/default [retrieved on-line May 2005].
    1. Bagatto MP. (2001). Optimizing your RECD measurements Hear J 54(9): 32, 34–36

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