Name the subjective property of sound related to its frequency.

The frequencies of notes given by flute, guitar and trumpet are respectively 400 Hz, 200 Hz and 500 Hz. Which one of these has the highest pitch?

Complete the following sentences :

If the amplitude of the sound is halved, it's loudness becomes …….. .

Name the characteristic which enables one to distinguish the sound of two musical instruments even if they are of the same pitch and same loudness.