Internal auditory hallucination
At the lowest level, internal auditory hallucinations generally consist of ill-defined, distant, and subtle sounds that stop as soon the person notices them. For example, a person may hear vague voices, music, and tones within their own head but find that they are not remotely discernable in terms of their given details.
Partially defined hallucinations
At this level, the hallucinations can be directly noticed without them immediately stopping, but are not fully defined in terms of their detail. This means that, although fully audible, they will still sound partially muffled and distant. For example, a person may hear voices or music within their own head but find that they do not sound quite as crisp and detailed as similar sounds that can be heard in real life.
Fully defined hallucinations
At this level, the hallucinations have become completely realistic and lifelike in terms of the detail of their sound. For example, a person may hear fully defined voices, music, or other sounds within their own head that are complex and fully defined in terms of their details.
External auditory hallucination
Partially defined embedded hallucinations
At the lowest level, the hallucinated sounds lack clarity and may be indistinct, muffled, and difficult to make out. They are also only heard embedded within real sounds occurring within the external environment. For example, a person may hear subtle music or voices embedded within the sound of the wind, cars, or rain. These hallucinations sound as if they are coming from an unspecifiable direction somewhere within the external environment.
Partially defined separate hallucinations
At this level, the sounds remain only partially defined, but are heard on a separate layer of their own instead of manifesting themselves as embedded within other noises. They will also begin to sound as if they are occurring from a vaguely specifiable direction or source within the external environment.
Fully defined separate hallucinations
At this level, the sounds become fully defined in their clarity, meaning that the content of the hallucinations can be recognized and heard perfectly as if they were physically present. They will also sound as if they originate from a specific location within the external environment in a manner so lifelike that it will often confuse the person into believing it was a real sound.
- Auditory hallucinations: a review of psychological treatments | https://www.schres-journal.com/article/S0920-9964(98)00052-8/abstract
- Paracusia (Medical dictionary) | http://medical-dictionary.thefreedictionary.com/paracusia
- The clinical spectrum of musical hallucinations (ncbi) | https://www.ncbi.nlm.nih.gov/pubmed/15546592
- The Omnipotence of Voices: A Cognitive Approach to Auditory Hallucinations (The British Journal of Psychiatry) | https://www.cambridge.org/core/journals/the-british-journal-of-psychiatry/article/omnipotence-of-voices/BF121CBA135062075365F28B5AA0ED94
-  N Stanciu, C., & M Penders, T. (2016). Hallucinogen Persistent Perception Disorder Induced by New Psychoactive Substituted Phenethylamines; A Review with Illustrative Case. Current Psychiatry Reviews, 12(2), 221-223. | http://www.ingentaconnect.com/contentone/ben/cpsr/2016/00000012/00000002/art00013#expand/collapse
- Al-Assmar, S. E. (1999). The seeds of the Hawaiian baby woodrose are a powerful hallucinogen. Archives of internal medicine, 159(17), 2090-2090. | https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/521620
- Nichols, D. E. (2016). Psychedelics. Pharmacological reviews, 68(2), 264-355. | https://dx.doi.org/10.1124%2Fpr.115.011478
- Lu, B. Y., Woofter, C., & Escalona, R. (2004). A case of prolonged peyote-induced psychosis resolved by sleep. The Journal of clinical psychiatry, 65(10), 1433. | https://www.ncbi.nlm.nih.gov/pubmed/15491253