What additional frequencies are tested when a 20 dB difference exists between adjacent frequencies?

When there is a 20 dB difference between adjacent frequencies during audiometric testing, it is common practice to test the interoctave frequencies. Interoctaves refer to the frequencies that lie halfway between the standard octave frequencies on the audiogram. For example, if testing occurs at 250 Hz and 500 Hz, an additional frequency of 300 Hz (the interoctave) would be tested to gain a more complete understanding of a person's hearing across the frequency spectrum.

This testing is especially important in cases where significant hearing loss is detected to ensure that any areas of loss are accurately identified, and no gaps in frequency response are overlooked. The inclusion of interoctave measurements helps to provide a more detailed audiometric profile of the individual being tested.

Other options do not fit this context: ultrasonic frequencies generally refer to sounds above the human hearing range, suboctave frequencies are typically not standard terminology used in audiometry, and superoctave frequencies do not correspond to the established protocol for addressing differences between adjoining frequencies. Hence, the identification of interoctave frequencies as the additional frequencies tested is notable for its relevance in clinical audiology practices aimed at comprehensive assessment.