The part of a. soundwave that we hear as loudness is

Explanation:

For most humans, zero dB marks the threshold for perception of sound, although loudness ultimately depends on both amplitude and frequency. The human ear is most sensitive to sounds between 1000 and 5000 Hz. The amplitude of a soft whisper is approximately 30 dB.

the right answer is it connects amino acids

not sure if this is what you'r looking for eubacteria and archaebacteria