Question on characteristics of sound?

In the classica lheory, amplitude and frequency are inependent. Any amplitude can have any frequency. Square of amplitude is energy equivalent. This says any frequency can have energy from 0 to infinity. But the freqency and wave length are related which the property of the medium.

Quote: " I have learned that pitch is proportional to frequency"

well, yes, but it is not DIRECTLY proportional to frequency;

pitch is proportional to the logarithm of the frequency
( each octave of increase in pitch is equivalent to a doubling of frequency, rather than an equal increase of frequency)

also "loudness" or "volume" is proportional to the logarithm of the amplitude
..... that is why we often use the decibel ( which is a logarithmic unit) to express sound intensities.

Quote: "So, is it that shrillness and frequency are independent of volume & amplitude? "

not sure that "shrillness" is a useful descriptive word in this context. (whereas "pitch" is useful).

Anyhow, pitch and loudness are very subjective, particularly as we all have auditory response curves, which continually change as we get bigger and older.

A young child can experience a high amplitude sound wave with frequency = 24 kHz as a very loud high pitched whistle that drowns out most other sounds.

While simultaneously, an 18 year old in the same room might only notice the high pitched tone as a fairly quiet whistle if most other sounds were reduced to a very low amplitude.

Meanwhile, a 30 year old would probably be totally unaware of the 24kHz tone even if every other sound was reduced to zero amplitude, in which case the 30 year old might only be aware of total silence.