Do silent farts smell worse?

The short answer is ‘yes’.

As this short animation from AsapScience explains, intestinal gases comprise mostly odourless gases such as oxygen, nitrogen and carbon dioxide. However sulphur compounds from the breakdown of food in the gut also escape during flatulence, and these are definitely not odourless.

Louder farts have a higher volume, and while they can contain sulphur compounds they are mostly odourless gas. Silent farts, on the other hand, have a lower volume and a higher sulphur concentration, and therefore tend to smell worse.