Which one of the following statements is not correct?

Statement 2 is incorrect because the sensitivity of the human ear varies significantly with frequency. Research on equal-loudness contours, such as the Fletcher-Munson and Robinson-Dadson curves, demonstrates that the ear is not equally sensitive to all frequencies in the audible range [3]. For instance, the ear is most sensitive to frequencies between 2000 Hz and 4000 Hz, while it is significantly less sensitive to low-frequency sounds [1]. Statement 1 is correct as the ear's response to intensity is approximately logarithmic, described by the Weber-Fechner law [2]. Statement 3 correctly describes the principle of superposition, where the resultant displacement is the algebraic sum of individual wave displacements. Statement 4 is also correct; longitudinal waves (like sound or P-waves) can propagate through solids, liquids, and gases [2].

Sources

1. [1] https://www.sciencedirect.com/topics/engineering/equal-loudness-contour
2. [3] https://en.wikipedia.org/wiki/Equal-loudness_contour
3. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC1994651/