- To provide insufficient amplification.
- 1933, Keith Henney, The Radio Engineering Handbook, page 286:
- In general, there is a tendency to underamplify the extreme ends of the musical scale and to overamplify certain particular frequencies below the middle, such as originate from acoustic resonance.
- 2006, Patricia Spencer, Advances in the Spoken-Language Development of Deaf and Hard-of-Hearing Children, →ISBN:
- Physiological thresholds can differ from behavioral thresholds by ±15–20 dB HL. Thus, without verification of behavioral responses with amplification, hearing aids may underamplify or overamplify.
- 2014, Michael J. Metz, Sandlin's Textbook of Hearing Aid Amplification, →ISBN:
- What is interesting to note here is that the 2⁄3 gain can be seen to overamplify over the curved line of the impaired ear more than underamplifies, whereas the 1⁄3 gain curve illustrates the opposite, where it tends to underamplify sound to the ear.