Which of the following statements about sound is incorrect?

Audible or sound waves are longitudinal mechanical waves with frequencies ranging from 20 to 20,000 Hz.

Infrasonic waves are longitudinal mechanical waves with frequencies less than 20Hz.

As a result of the preceding points, we arrive at the following conclusion:

Sound travels at a constant speed regardless of pressure.

The speed and wavelength of sound change as it travels from one medium to another.

In humid air, sound travels faster.

The speed of sound is greatest in solids and lowest in gases.