The bug
When silverfish (or endermites) move around, they don't make any footstep sounds or subtitles. There are sound events for footsteps (entity.silverfish.step, entity.endermite.step), but the game doesn't use them, nor does it use the default footstep sounds.
All other mobs (including blazes and withers on the ground) make footstep sounds, so this seems inconsistent.
Code analysis
Based on 1.11.2 decompiled using MCP 9.35 rc1
Silverfish and endermites override the method net.minecraft.entity.Entity.canTriggerWalking() to return false. This causes them to not make walking / swimming sounds and does not slow them down on slime blocks or causes magma block damage (see also MC-102267).
Additional updated code analysis can be found in this comment.
Linked issues
is duplicated by 3
relates to 2
Attachments
Comments 33
Can confirm for 20w26a, it's not just OP. They don't use the sounds in my game, and the wiki mentions that these sounds are unused in Java, but are used in Bedrock.
Can confirm in 21w03a. Relates to MC-210282.
When I have played in 1.13.1 I did hear them make sounds. So this may be a problem solely on your device.