Which wave property is associated with sound intensity?

Sound intensity is directly related to amplitude. Amplitude refers to the maximum extent of a vibration or oscillation from its rest position, which in the case of sound waves, determines how loud the sound is perceived. When the amplitude of a sound wave increases, this leads to a corresponding increase in sound intensity, meaning the sound will be heard as louder.

Other properties such as frequency, wavelength, and speed do play important roles in the characteristics of sound waves, but they do not correlate with sound intensity in the same way that amplitude does. Frequency relates to the pitch of the sound, wavelength is the distance between successive peaks of the wave, and speed is how fast the sound wave travels through a medium. While these properties are essential to understand sound as a whole, it is amplitude that specifically determines the intensity or loudness of the sound produced.