Hearing Aid Fitting—Theoretical and Practical Views

The purpose of this investigation was to study the impact of spectral shape and content on thresholds of discomfort (TD) for listeners with normal hearing and listeners with hearing loss. Secondary to that purpose was to quantify binaural summation at high intensities across complex stimulus conditions for both groups of listeners. Forty subjects (20 with normal hearing, 20 with hearing loss) participated. Complex acoustic stimuli (multitone and continuous discourse) were filtered to have four spectral shapes: (1) flat spectrum, (2) long-term average speech spectrum, (3) reverse long-term average speech spectrum, and (4) theTD contour derived for each subject from pure-tone TD obtained with eight pure tones from 250 to 4000 Hz. The results suggest that (1) TD for complex stimuli are lower for subjects with hearing loss compared with those with normal hearing, suggesting increased loudness summation with this population; (2) binaural summation of approximately 6 dB (independent of stimulus type, filter shape, or spectral content), indicating that a correction of similar magnitude for bilateral hearing aid fittings is appropriate; and (3) TD obtained at 750, 1500, and 3000 Hz accounted for approximately 60 percent of the variance in the complex TD measures, suggesting that TD at these frequencies be used to set the output obtained from a hearing aid with a 90–dB pure-tone sweep as the input stimulus. Abbreviations: ANOVA = analysis of variance, FIR = finite-impulse response, FS = flat spectrum, LTASS = long-term average speech spectrum, OSPL90 = output obtained from a hearing aid with a 90–dB pure-tone sweep as the input stimulus, R-LTASS = reverse long-term average speech spectrum, TD = threshold(s) of discomfort, TD contour = spectrum derived from TDs obtained with eight pure tones from 250 to 4000 Hz

Effect of Spectral Shaping and Content on Loudness Discomfort

Bentler

Nelson²

2001

Quantifying and Responding to Patient Needs and Expectations

Palmer¹

2005

Comprehensive audiometric testing serves as the cornerstone of adult hearing aid fittings for many clinicians. The data will serve to define the degree, configuration, and site of lesion of the hearing loss. The data will be used in prescriptive formula to preset the hearing aid and may be entered into probe microphone or hearing aid test box equipment to provide verification targets. Clinicians are comfortable obtaining audiometric data, have an accepted way of obtaining these data, and are comfortable discussing these data with patients and other professionals. The patient, however, is not a walking audiogram and may bring all sorts of interesting nuances to the process. Just as part of the clinician's comfort with using audiometric data comes from the standard process of obtaining and reporting these data, the clinician who chooses to go beyond the audiogram in terms of data collection with a patient must have a means for gathering and quantifying additional information. The following case describes a method of obtaining and quantifying the patient's listening and communication needs. The case illustrates the use of these measures in recommending appropriate communication and safety solutions.

Estimates of Loudness, Loudness Discomfort, and the Auditory Dynamic Range: Normative Estimates, Comparison of Procedures, and Test-Retest Reliability

Sherlock

Formby²

2005

The purpose of this series of experiments was to establish normative reference values for absolute and relative judgements of loudness discomfort and for the auditory dynamic range (DR), and to evaluate intersubject variability and intra-subject test-retest reliability for the respective measures of loudness discomfort. To establish the normal auditory DR, audiometric thresholds and loudness discomfort levels (LDLs) were measured from a group of 59 normal-hearing adults without sound tolerance problems. The resulting estimates of the LDL and DR were on the order of 100 dB HL and 95 dB, respectively. A subset (n = 18) of this larger group participated in further studies in which loudness growth functions and the upper limit of the auditory DR were measured by categorical scaling judgments. The findings revealed no significant differences between the test methods for absolute (LDL) and relative (categorical scaling) judgements of loudness discomfort, intersubject variability, or intrasubject test-retest reliability, and suggest that the simple LDL estimate of loudness discomfort is an efficient and valid clinical measure for characterizing the "threshold of discomfort."