A comparison of procedures in "otometry": absolute versus equal-loudness judgments

Area of Science:

• Audiology and Psychoacoustics
• Hearing Science
• Acoustics

Background:

• Establishing a precise "normal" loudness level is crucial for audiological assessments.
• Previous methods for determining comfortable loudness levels have shown variability.
• Understanding loudness perception across different frequencies is essential for hearing aid fitting and research.

Purpose of the Study:

• To determine the "normal" (most comfortable) loudness levels for normal-hearing individuals across a range of frequencies.
• To compare the reliability of estimating "normal" loudness versus making equal-loudness judgments.
• To evaluate the potential of equal-loudness procedures for audiological testing (Otometry).

Main Methods:

• Twenty normal-hearing participants judged signal trains at varying frequencies (0.35 to 4 kHz) to identify "normal" to "loud" and "normal" to "soft" transition points.
• "Normal" loudness was defined as the midpoint between these transition zones.
• Participants also performed equal-loudness judgments, adjusting other frequencies to match a standard 1 kHz loudness level (72.8 dB SPL).

Main Results:

• Replication showed 70% of participants could reproduce "normal" loudness within 9 dB across all frequencies, but only 35% within 6 dB.
• The mean "normal" loudness at 1 kHz was 72.8 dB SPL (re 20 μPa).
• Variances for equal-loudness judgments were 2-3 times smaller (better) than for "normal" loudness estimations.

Conclusions:

• Equal-loudness judgment procedures demonstrate higher reliability compared to direct "normal" loudness estimations.
• The study supports the recommendation of utilizing equal-loudness measurement procedures, such as Victoreen's method, for audiological applications.
• This approach may offer a more precise and consistent method for assessing hearing sensitivity and loudness perception.