The afferent auditory pathway transmits acoustic information from the inner ear via the auditory nerve to various brainstem nuclei up to the auditory cortex. It includes the vestibulocochlear nerve (VIII cranial nerve), the cochlear nucleus and higher central structures. Disorders in this pathway lead to sensorineural hearing loss and central auditory processing disorders. Objective measurement methods such as the brainstem response (ABR) test the integrity of the afferent auditory pathway. An intact afferent auditory pathway is a prerequisite for understanding speech and localizing sound sources.

Ageusia refers to the complete loss of the sense of taste and occasionally occurs in combination with hearing and balance disorders. It can be caused by damage to the chorda tympani nerve, which transmits taste signals from the tongue to the brain. Patients also complain of reduced saliva production and loss of appetite. In ENT diagnostics, ageusia is often examined together with olfactory tests. Treatment depends on the underlying cause, such as infection or trauma.

Air conduction describes the transmission of sound waves via the air through the outer ear and middle ear to the inner ear. It is the primary auditory pathway for normal everyday sounds and is shown on audiograms as an air conduction curve. Deviations between air and bone conduction indicate conductive hearing loss. Measurements of air conduction make it possible to differentiate between middle ear and inner ear disorders. Clinically, air conduction is measured using headphone audiometry.

In an auditory context, accommodation refers to the adaptation of the auditory system to changing sound pressure levels through muscular tension of the auditory ossicles. This mechanism protects the inner ear from loud stimuli and optimizes sensitivity to quiet signals. Accommodation takes place within milliseconds and is controlled by the stapedius and tensor muscles. If the muscles or nerves are damaged, the protective reflex can fail, which increases the risk of noise damage. Audiometrically, impaired accommodation is reflected in altered reflex thresholds.

Active listening training includes targeted exercises to improve auditory perception and speech intelligibility, especially in difficult listening situations. Various sound patterns and speech signals are presented in order to strengthen central processing skills. Studies show that regular training promotes neuronal plasticity in the auditory cortex. Areas of application include tinnitus therapy, rehabilitation after sudden hearing loss and support for central hearing disorders. Modern programs use computer-assisted tasks and biofeedback.

Acoustics is the study of the generation, propagation and perception of sound. It forms the basis for all audiological measurement methods and the development of hearing aids. Within acoustics, a distinction is made between airborne, bone and structure-borne sound. Applied acoustics deals with room acoustics, noise protection and soundproofing measures. In hearing aid technology, acoustic principles are incorporated into filter design and amplifier technology.

Auditory hallucinations are the perception of voices or sounds without an external sound source. They can have psychological causes (e.g. schizophrenia) or neurological lesions. In audiology, they are distinguished from tinnitus, as hallucinations can carry linguistic content. Neuropsychological tests and imaging procedures are used for diagnosis. Psychotherapy and medication are used therapeutically.

The acoustic reflex test measures the stapedius reflex, which reacts to loud sounds by contracting the stapedius muscle. This reflex protects the inner ear from overloading and can indicate middle ear or brain stem lesions. Reflex failures on one or both sides provide a differentiated diagnosis of conductive and sensorineural hearing loss. The test is carried out using tympanometry devices that record reflex thresholds and latencies. It is clinically important for neural hearing disorders and otosclerosis.

In hearing aids, acoustic signal processing refers to the conversion of microphone signals into optimized sound signals for the wearer. Digital chips filter out background noise, amplify speech and dynamically adapt to the environment. Techniques such as feedback suppression and adaptive directional microphones improve hearing quality in noisy environments. Advanced systems use AI to learn hearing preferences and automatically recognize scenes. Signal processing is crucial for natural hearing with hearing systems.

The stapedius reflex is an involuntary contraction of the stapedius muscle in response to an intense sound stimulus. Lifting the stapes footplate reduces the transmission of sound to the inner ear and protects it. Reflex measurements provide information about the function of the middle ear, facial nerve and brain stem. A missing or asymmetrical reflex response can indicate otosclerosis or cranial nerve damage. The reflex is part of the standard tympanometry in audiological diagnostics.

Acoustic trauma is caused by sudden, extremely loud sound events such as explosions or blasts. It leads to hair cell damage in the inner ear, which is often accompanied by tinnitus and permanent hearing loss. Immediate measures include corticosteroids to reduce inflammation and high-pressure oxygenation. Long-term consequences can include impaired speech intelligibility and hyperacusis. Prevention through hearing protection is crucial to avoid acoustic trauma.

Presbyacusis is the gradual, physiological loss of hearing in old age. Hair cells in the inner ear and neuronal connections are mainly affected, which leads to reduced speech comprehension. Symptoms are particularly noticeable in the high frequency range and with background noise. Hearing aids and hearing training can significantly improve quality of life and communication. Preventive measures such as noise protection and nutrition play a supporting role.

The alveolar membrane in the inner ear is a fine layer that carries hair cells in the organ of Corti and converts vibrations into neuronal signals. It ensures precise frequency separation along the cochlea. Changes or damage to the membrane impair pitch recognition and volume perception. Histological studies show that age and exposure to noise reduce the elasticity of the membrane. Biological research aims at regenerative therapies to restore this membrane.

The anvil is the middle of the three auditory ossicles in the middle ear and transmits vibrations from the malleus to the stapes. It acts as a lever that increases the sound pressure before the vibrations are transmitted to the inner ear. Through this amplification, the anvil ensures efficient conversion of airborne sound into bone sound. Functional disorders such as ossification (otosclerosis) can cause conductive hearing loss. For detailed information on the sound conduction chain and test procedures, see the Rinne and Weber test.

The amplitude describes the deflection of a sound wave and determines the perceived volume. It is measured as the sound pressure level in decibels and correlates directly with the perception of hearing. High amplitudes can lead to hair cell damage, while low amplitudes are close to the hearing threshold. In audiometry, the amplitude indicates the dynamic bandwidth of hearing. Technical applications regulate amplitudes to minimize distortion in hearing aids.

Amplitude modulation (AM) refers to the change in sound amplitude following a modulation signal, such as speech or music signals. In hearing tests, AM is used to test the ear's sensitivity to modulation. A reduced perception of AM can indicate central auditory processing disorders. In hearing aids, AM detection helps to separate speech from background noise. Psychoacoustic experiments with AM provide insights into neuronal coding mechanisms in the auditory system.

Anacusis refers to the complete loss of hearing in which neither air nor bone conduction nor the slightest acoustic stimuli can be perceived. It can be congenital or caused by severe damage to the inner ear, auditory nerve or central auditory pathways. Those affected are completely dependent on visual and tactile aids such as sign language or vibro-alerts to communicate. Medically, anacusis is tested using sound and speech audiometry as well as otoacoustic emissions and evoked potentials to determine the extent and origin of the damage.

Analog hearing aids amplify acoustic signals continuously without digital signal processing. They work with simple amplifier stages and filters, are inexpensive but less flexible than digital models. Adjustments are made mechanically or via potentiometers, which makes fine-tuning difficult. Today, analog devices are rarely used, mainly in simple applications or as a backup. Their sound quality is considered less natural than digital systems.

Anisoacusis describes a different hearing threshold in both ears, often caused by unilateral middle ear or inner ear damage. Audiometrically, there is an asymmetry between the air and bone conduction curves. Clinically, anisoacusis may indicate otosclerosis, Meniere's disease or neural lesions. Treatment depends on the cause, such as surgical intervention or hearing aid fitting. Monitoring of anisoacusis helps to assess the course of the disease and the success of therapy.

Antiemetics relieve nausea and vomiting that occur in vestibular disorders such as inner ear inflammation. They usually act on histamine or dopamine receptors in the vomiting center. By reducing accompanying symptoms, they improve the therapeutic tolerance of vestibular training. Long-term use requires monitoring, as side effects such as fatigue can occur. In ENT practice, antiemetics are combined with vestibular rehabilitation for optimal results.

Vestibular dysfunctions affect areas of the brain that control appetite and nausea. Disorders of vestibular perception often lead to eating disorders and weight loss. Therapies include vestibular training and pharmacological support to normalize eating behavior. Dietary recommendations with easily digestible foods reduce accompanying symptoms. Interdisciplinary care by ENT, neurology and nutritional therapists improves quality of life.

Arbitrary sound sources are unpredictable, random sounds in the environment that do not belong to speech patterns. They make it difficult to understand speech and increase the cognitive load when listening. Hearing aid algorithms must recognize and filter out such noise. Laboratory tests with arbitrary signals test the robustness of hearing systems. Psychoacoustic studies investigate how the brain separates arbitrary sounds from relevant signals.

The arterial pressure in the inner ear ensures sufficient blood supply to the hair cells and neuronal structures. If the pressure drops, this can lead to ischemia and hearing loss. Vascular examinations measure blood flow parameters in order to detect vascular bottlenecks. Treatment options range from drug treatment to microsurgery. Stable perfusion is crucial for hearing health and the regeneration of sensory cells.

The articulation index (AI) indicates the proportion of speech sounds that are correctly reproduced by a hearing aid user. It is measured in speech audiometry and presented as a value between 0 and 1. A high AI (> 0.7) means good speech intelligibility, low values indicate a need for adaptation. AI measurements help to optimize hearing aid programs and document rehabilitation progress. The index correlates closely with subjective hearing comfort in everyday life.

In ear canal atresia, the external auditory canal is congenitally missing, which leads to complete conductive blockage. Those affected suffer unilateral or bilateral conductive hearing loss. Surgical opening (atresieplasty) can partially restore hearing. Audiological care includes bone conduction hearing systems until the operation. Long-term follow-up checks scarring and hearing gain.

An audiogram is a graph that shows hearing thresholds across different frequencies. Air and bone conduction are measured separately to distinguish conductive from sensorineural hearing loss. Normal values are 0-20 dB; deviations indicate degrees of loss. Audiograms are the basis of every hearing medical diagnosis and treatment planning. Modern digital audiometers automatically save and compare curves.

An audiologist is a medical specialist or scientist who specializes in the diagnosis and treatment of hearing and balance disorders. They carry out complex tests such as AEP, OAE and speech audiometry. Audiologists work on an interdisciplinary basis with ENT doctors, neurologists and hearing aid acousticians. They develop individual rehabilitation plans and provide long-term support for patients. Their training encompasses medicine, neuroscience and technology.

Audiology is the interdisciplinary field that deals with hearing, balance and auditory processing. It combines aspects of medicine, physics, psychology and technology. Audiologists research hearing mechanisms, develop diagnostic procedures and optimize hearing aids. Clinical audiology includes screening, differential diagnostics and therapy. The aim is to maintain and improve the ability to hear and communicate.

Audiometry refers to all measurement methods for determining hearing thresholds and speech intelligibility. This includes sound, speech and objective measurements such as OAE and AEP. The results are used in hearing aid fitting and therapy monitoring. Modern audiometry devices use computer-aided procedures and automated protocols. Regular audiometry is used to monitor the progress of noise work or ototoxic medication.

Auditory evoked potentials are electrical signals in the brain that are measured in response to sound stimuli. They allow objective assessment of the auditory pathway from ear to cortex. AEPs are used for newborn screening, suspected brain stem lesions and neurological diseases. Different wave components provide information about individual stations of the auditory pathway. The examination is carried out using scalp electrodes, without the active cooperation of the patient.

Auditory feedback occurs when hearing aid microphones pick up the amplified sound from the listener again and enter a feedback loop. This manifests itself as whistling or humming and can severely impair the listening experience. Modern hearing systems use adaptive algorithms to detect and suppress feedback in real time. Acoustic adjustments such as tight earmolds further reduce the risk. An optimal microphone-hearer distance design already minimizes feedback mechanically.

Auditory processing comprises the central processes for analyzing and interpreting sound signals in the brain. It includes feature extraction, speech comprehension and sound localization. Auditory processing disorders manifest themselves in difficulties understanding speech in background noise. Neuropsychological tests and central audiometry procedures help with the diagnosis. Rehabilitation through auditory training aims at plasticity of the auditory cortex.

The auditory cortex in the upper temporal lobe is the central processing station for sound information. This is where the frequency, volume, rhythm and direction of sound are evaluated. Plastic changes in the cortex enable learning processes such as auditory training and tinnitus management. Lesions lead to central hearing disorders and speech comprehension deficits. Imaging techniques (fMRI, PET) examine activity patterns during acoustic stimuli.

The ABR measures waves of electrical activity along the auditory pathway in the brainstem following click stimuli. It is used for the objective diagnosis of hearing thresholds and neural conduction disorders. ABR is standard in newborn screening and in cases of suspected acoustic neuroma. Analysis of the wave latencies allows conclusions to be drawn about lesion locations from the ear to the brain stem. Examination is painless using scalp electrodes.

Auricular stimulation uses electrical or mechanical stimuli on the auricle to influence neuronal networks. It is used in pain therapy, tinnitus treatment and vestibular rehabilitation programs. Stimulation can promote blood circulation and stimulate neuronal plasticity. Clinical studies are investigating effects on chronic tinnitus and dizziness. Safety profile is considered good, side effects are rare.

Auriculotherapy is a form of ear acupuncture in which certain points on the auricle are treated in order to achieve systemic effects. It is also used to treat tinnitus, dizziness and stress. Its effectiveness is scientifically controversial, but patients report subjective improvement. Points that correspond to certain organs and nerve reflex zones are treated. Auriculotherapy is part of integrative ENT and pain therapy concepts.

The outer ear comprises the pinna and external auditory canal and conducts sound waves to the eardrum. The shape of the outer ear amplifies certain frequencies and supports directional perception. Diseases such as exostoses or otitis externa impair sound reception. Audiological examinations check the patency and resonance of the outer ear. Surgical interventions can restore form and function in the case of malformations.

Autophone refers to the perception of one's own voice via bone conduction, which leads to a muffled sound. This effect occurs because vibrations reach the inner ear directly via the bones of the skull. When we speak, we perceive our voice as louder and fuller than others. Autophony can occur more frequently in the case of tube dysfunction or after middle ear surgery. Audiometric tests separate air conduction from bone conduction in order to diagnose autophony.