Phonophobia, also called ligyrophobia or sonophobia, is a fear of or aversion to specific sounds—a type of specific phobia. Occasionally it is called acousticophobia. Although some sounds could be feared by most people, such as certain loud sounds or sounds that signal threats, fears of these sounds would not be considered phonophobia unless the amount of fear and anxiety was disproportionate. In phonophobia, the feared sounds may be ones that are soft and non-damaging, such as kitchen sounds or a door closing. Another example is watching someone blow up a balloon beyond its normal capacity. This is often an unsettling, even disturbing thing for a person with phonophobia to observe, as they anticipate a loud sound when the balloon pops.

Phonophobia generally leads to anxiety around and avoidance of contexts where individuals might be exposed to feared sounds. Such avoidance could risk making the auditory system more sensitive.

The term phonophobia comes from Greek φωνή - phōnē, "voice" or "sound" and φόβος - phobos, "fear".

The word phonophobia is also sometimes used in neurology to refer to sound intolerance observed in people who experience migraine headaches, especially during migraines. The presence of such sound intolerance may be used to support the diagnosis of migraine. Definitions and measures of the sound intolerance that can accompany migraines emphasise that it involves feelings of discomfort and auditory pain, implying that the type of sound intolerance described would actually be hyperacusis and not phonophobia. At the very least, the concept of phonophobia as used in relation to migraine is different from the concept of phonophobia as a specific phobia of certain sounds.

Although phonophobia can arise as a secondary consequence of other sound tolerance conditions, this does not make it synonymous with them. As phonophobia refers specifically to irrational fears of sounds, not rational ones, phonophobic fear, anxiety, and avoidance would need to exceed the level expected due to the discomfort or pain caused by any other sound tolerance conditions.

One other sound tolerance condition that can sometimes be observed alongside phonophobia is hyperacusis, or discomfort or even pain caused by sounds that most people would not consider uncomfortably loud. Indeed, phonophobia is sometimes referred to as a specific type of hyperacusis, fear hyperacusis, although other authors regard hyperacusis and phonophobia as distinct conditions, insofar as hyperacusis involves discomfort caused by a physical sound whereas phonophobia does not.

Another type of sound intolerance that can co-occur with phonophobia is misophonia, or emotional reactions to specific trigger sounds that need not be loud (e.g., anger in response to chewing sounds). Indeed, phonophobia has even been conceptualised as a type of misophonia. However, other sources regard the specific phobia of phonophobia as being distinct from the emotional reactions characteristic of misophonia.

Moreover, phonophobia may co-occur with tinnitus (perception of sounds, especially ringing sounds, without an external source) or with generic noise sensitivity (sensory processing sensitivity towards sounds).