Auditory suppression

Auditory suppression is a reduction in the perceived loudness and clarity of external sounds.

As a drug effect it is acute and dose-proportional, fading as the substance wears off; this distinguishes it from clinical hearing loss or deafness. It ranges from a mild muffling of background noise to a near-complete absence of auditory input at high doses.

Auditory suppression is commonly reported across several pharmacological classes. It is most consistently induced at moderate to high doses under dissociatives such as ketamine, dextromethorphan, and 3-MeO-PCP, and under deliriants such as diphenhydramine and grayanotoxin. It also appears under opioids such as heroin and depressants such as clonidine.

Auditory suppression is felt as a receding of the sonic environment: sounds that would normally register clearly arrive muffled, distant, or stripped of detail, as though heard through thick walls or under water. Speech becomes difficult to follow; ambient sound loses its texture and presence.

The effect is largely passive — sounds are perceived as existing but cannot be fully resolved. At high doses, particularly under dissociatives, the auditory field can narrow to near-silence, with only the loudest sounds breaking through.

Auditory suppression arises through different pathways depending on the drug class:

• Dissociatives — block NMDA receptors, interrupting thalamocortical sensory relay and muffling the brain's processing of auditory input.
• Deliriants — antagonize muscarinic acetylcholine receptors, impairing the cholinergic circuits that govern sensory gating.
• Opioids — act at opioid receptors in brainstem nuclei that modulate ascending sensory signals, attenuating auditory throughput.
• Depressants — enhance central inhibitory tone, reducing overall sensory responsiveness.

How much each pathway contributes in a given case is not fully understood.

Who experiences it, and how strongly, varies widely. Dose is the primary driver — suppression is minimal at low doses and deepens markedly at higher ones. The drug class matters: dissociatives tend to produce the deepest suppression, while depressants and opioids produce a subtler form.

Individual differences in auditory sensitivity and prior exposure also shape the experience. Unlike more affect-laden effects, auditory suppression is not strongly expectation-driven; a person who attends closely to the muffling may notice it more, but the effect follows dose more reliably than mindset.