Theres a trend of internalization of external perceptions, which means patients will locate the source of their hallucination from external objects to internal subjectivity over time. Phenomenological study
According to the study conducted by Tony Nayani and Anthony David in 1996, about half of the patients(46%) with audible thoughts claimed that the hallucination has somehow taken the place of their conscience in making decisions and judgement. They tend to follow the voices instructions when confronting dilemmas in their daily lives. The study also suggests that a majority of the patients, both male and female, labeled the sounds they heard as male voices. However, younger patients tend to hear younger voices, which suggests that the voices in the hallucination may share age with the patients but not gender. Whats more, voices in the hallucination usually differ from the patients own voices in accents. They reported the voices they heard as coming from different regions or social classes with them.Some patients may develop skills to control their hallucinations to a certain extent through some kind of cognitive focusing. They cant eliminate the voices, but through cognitive focusing or suggestive behaviours (e.g. swallowing), they can control the onset and offset of their hallucination. Pathophysiology
Studies have suggested that damage to specific brain areas may relate to the formation of audible thought. Patients who attribute the hallucination to an external locus are more likely to report the voice coming from the right. This unilateral characteristic can be explained by either contralateral temporal lobe disease or ipsilateral ear disease.
This should be distinguished from the commonly experienced phenomenon of getting a song stuck in ones head. Reports have also mentioned that it is also possible to get musical hallucinations from listening to music for long periods of time. Other causes include hearing loss and epileptic activity.In the past, the cause of auditory hallucinations was attributed to cognitive suppression by way of executive function failure of the frontoparietal sulcus. Newer research has found that they coincide with the left superior temporal gyrus, suggesting that they are better attributed to speech misrepresentations. It is assumed through research that the neural pathways involved in normal speech perception and production, which are lateralized to the left temporal lobe, also underlie auditory hallucinations. Auditory hallucinations correspond with spontaneous neural activity of the left temporal lobe, and the subsequent primary auditory cortex. The perception of auditory hallucinations corresponds to the experience of actual external hearing, despite the absence of any sound itself. Causes
In 2015 a small survey reported voice hearing in persons with a wide variety of DSM-5 diagnoses, including:

Bipolar disorder
Borderline personality disorder
Depression (mixed)
Dissociative identity disorder
Generalized anxiety disorder
Major depression
Obsessive compulsive disorder
Post-traumatic stress disorder
Psychosis (NOS)
Schizoaffective disorder
Schizophrenia
Substance-induced psychosisHowever, numerous persons surveyed reported no diagnosis. In his popular 2012 book Hallucinations, neurologist Oliver Sacks describes voice hearing in patients with a wide variety of medical conditions, as well as his own personal experience of hearing voices. Genetic correlations have been identified with auditory hallucinations, but most work with non-psychotic causes of auditory hallucinations is still ongoing.