In my reading, I noticed the descriptions of auditory imagery (or lack there of). In particular, whenever a situation is frightening Marlow describes the silence. As I pondered this in my reading, I noticed how silence paralleled to nature, in the fact that 
they are both uncontrollable. In nature, things are uncontrollable because of all of the different ecosystems, biomes, and constant energy. With silence, is it uncontrollable because of the lack of sound, or silence taking over as a presence?
–Steph
onlyfriendsstealyourbooks 
I have also been tracking the importance of silence and the role it plays in Heart of Darkness. I think the repeated lack of silence emphasizes the lack of information the readers recieve from Conrad throughout the story.
-Melvyna-
You question is so intriguing!The world silence itself has ominous and mysterious connotations.There is silence when you honor someone who has died, and also a weighty silence when you abstain from speaking (especially against something that is wrong). Conrad frames the story so that silence represents the contrast between the West and Africa. In the beginning of the Heart of Darkness, the narrator and his crew sit in silence until Marlow begins his story. To westerners silence is something that needs to be penetrated and filled. If language is so vital to life in the West, silence could even refer to death. The disturbance of silence parallels imperialism in a way– noisy steamers pierce the silence of nature in the Congo “always mute with an air of whispering, ‘Come and find out’” (19).
Lizzy