The spiral ganglion is a nerve cell ganglion inside the cochlea in which the cell bodies of the auditory nerve fibers (bipolar neurons) are located. It receives electrochemical signals from the hair cells and transmits action potentials to the brain stem via the vestibulocochlear nerve. Damage or degeneration in the ganglion spirale, for example due to age or ototoxins, leads to sensorineural hearing loss. Researchers are investigating how electrical stimulation of the ganglion can improve the performance of cochlear implants. Histological studies show that residual cell populations are crucial for the success of an implantation.

In psychoacoustics, gating describes the modulation of a sound signal through an on-off window in order to examine the onset and decay of the signal. It is used to analyze how quickly the ear reacts to the onset or cessation of a sound and how precisely the listener recognizes the signal boundaries. These measurements provide insights into temporal resolution and neuronal processing speeds in the auditory system. Clinically, gating helps to diagnose central auditory processing disorders. Experiments show that gating abilities decrease with age and hearing loss.

Sign language is a fully-fledged visual-gestural language used by deaf and hard of hearing people to communicate. It has its own grammar rules, syntax and vocabulary, independent of spoken languages. It plays an important role in hearing rehabilitation as an alternative form of communication. Interpreters and subtitles complement media services for sign language users. Research into the neurolinguistics of sign language shows that the same areas of the brain are activated as with spoken languages.

Ear training includes systematic training to train musical and linguistic hearing, for example to recognize intervals, chords or speech sounds. It promotes neuronal plasticity in the auditory cortex and improves differentiation and discrimination skills. In audiotherapy, auditory training is used to treat central auditory processing disorders. Software-supported programs offer adaptive exercises and feedback. Long-term training increases speech intelligibility, especially in noisy environments.

The external auditory canal conducts sound to the eardrum and, due to its shape, creates resonances in the frequency range of 2-4 kHz, which favors speech comprehension. It is lined with skin and cerumen glands, which produce earwax and prevent infections. Exostoses or cerumen obstructions impair sound conduction and lead to hearing loss. Otoscopic examination and cleaning are standard in ENT practice. Surgical procedures on the ear canal require preservation of skin integrity to avoid scarring and stenosis.

The hammer, anvil and stirrup form the chain of ossicles in the middle ear, which mechanically amplify sound pressure from the eardrum to the oval window. Their leverage increases the sound pressure by about 1.3 times before vibrations are transmitted to the inner ear. Joints and muscles (stapedius, tensor tympani) regulate stiffness and protect against loud stimuli. Diseases such as otosclerosis ossify these structures and cause conductive hearing loss. In surgery, prostheses or stapes otoplasties are used to restore mobility to the chain.

Hearing protection prevents noise damage by attenuating harmful sound pressure levels and is available in various forms: Earplugs, earmuffs or customized earmoulds. Protection factors (SNR, HML) provide information about attenuation performance in different frequency ranges. Correct fit and wearing comfort are crucial for effectiveness and acceptance. Legal requirements for noise protection apply in industrial and leisure environments. Modern electronic hearing protectors allow speech to be understood while at the same time protecting against impulse and continuous sound.

The hearing threshold is the lowest sound pressure level that can just be perceived and varies with frequency. It is plotted on the audiogram as a function of frequency and defines normal hearing (0-20 dB HL). Shifts in the threshold indicate hearing loss and determine the need for care. Thresholds are determined by tone audiometry under standardized conditions. Long-term courses show progression of noise damage or therapy effects.

Hearing training includes exercises to improve sound and speech perception, e.g. pitch, rhythm or speech comprehension tasks. It uses neural plasticity to strengthen central auditory processing after hearing loss or CI implantation. Computer-based programs adapt difficulty levels and provide immediate feedback. Studies show significant improvements in dB thresholds and discrimination skills. Integration in rehabilitation increases suitability for everyday use and communication comfort.

Hearing loss describes a reduction in hearing ability, subdivided into conductive, sensorineural and combined forms. Causes range from cerumen obstruction to noise trauma and neuronal lesions. The degree and frequency range of the loss are documented in the audiogram. Treatment options include hearing aids, implants or surgery. Early detection and intervention significantly improve prognosis and quality of life.

Hearing amplification is usually provided by hearing aids or implants that increase sound pressure or provide electrical stimulation. Digital hearing systems offer frequency-selective amplification and compression to make soft sounds audible and loud sounds tolerable. Amplification profiles are individually adapted to the audiogram. Excessive amplification can cause feedback or discomfort. Fine adjustment by the acoustician optimizes speech intelligibility and sound quality.

Hearing delay refers to a delay in sound perception, for example due to central processing difficulties or hearing system latencies. Latencies of over 10 ms can impair speech comprehension and audio-video synchronization. In digital hearing aids, latency is minimized by fast signal processors. Diagnostically, evoked potentials and reaction times are measured in dichotic or latency tests. Rehabilitation aims to reduce central delays through training.

In the case of hypersensitivity or central processing disorders, normal background noise can lead to mental exhaustion. Those affected complain of concentration problems, headaches and stress. Therapy includes hearing training, cognitive behavioral therapy and the targeted use of hearing protection. Adaptation of the working environment and breaks reduces symptoms. Research investigates the neuronal correlates of auditory fatigue.

The gelatine membrane is the middle, connective tissue layer of the eardrum and gives it tensile strength and elasticity. It consists of collagen fibers in a radial and circular arrangement. Injuries or perforations to this layer impair the ability to vibrate and lead to conductive hearing loss. In tympanoplasty, the gelatin skin is replaced with grafts to restore integrity and function. Histological studies investigate healing processes and scarring.

General masking adds broadband noise to the test signal to prevent cross-hearing and unwanted co-reactions. In audiometry, it ensures valid threshold determinations on both sides. Masking level is based on interaural attenuation values. Incorrect masking can falsify test results, correct protocols are defined in standards.

Noise is a sound event with an irregular or complex frequency spectrum that is not perceived as a musical tone. It can be disturbing (noise) or pleasant (natural sounds), depending on the context and volume. In psychoacoustics, parameters such as loudness, masking and emotional response are investigated. Noise management in working and living areas serves health and comfort goals.

Sound sensitivity refers to the individual reaction to acoustic stimuli, ranging from normal hearing to hyperacusis. Patients with hyperacusis perceive moderate volumes as painful or stress-inducing. Comfort and discomfort thresholds are determined diagnostically. Therapy includes desensitization training and cognitive procedures. Targeted hearing protection prevents additional sensory overload.

A sound level meter measures sound pressure levels in dB (A) or dB (C) and is used in industry, environmental and health studies. Modern Class 1 meters offer high accuracy and frequency weighting according to standards. Mobile apps use smartphone microphones, but are less accurate. Calibration and correct placement are a prerequisite for reliable data.

The organ of balance in the inner ear consists of the semicircular canals and the otolith organs (sacculus, utriculus). It registers rotational and linear accelerations and sends information about head position and movement to the brain. Disturbances lead to dizziness, nausea and unsteadiness when walking. Diagnostic tests include caloric testing, VEMP and videonystagmography. Rehabilitation includes vestibular training to compensate.

A bell filter (peak filter) emphasizes or attenuates a narrow frequency band around a mid-frequency and is used in hearing aids for fine-tuning. The filter has two transition slopes whose steepness is defined by a Q factor. Bell filters can be used to correct specific resonances or interfering frequencies. They are part of multi-band equalizers and compression systems.

Glutamate is the primary neurotransmitter released by inner hair cells at the synaptic cleft to transmit auditory signals to afferent neurons. The amount and speed of glutamate release influences the temporal precision of signal transmission. Dysregulation can lead to synaptic deterioration and hidden hearing loss. Research is investigating glutamatergic modulators to protect synapses in noise trauma.

Goodness of fit evaluates how well a hearing aid signal corresponds to the target frequency response specified by the audiogram. It is measured as a curve deviation in dB over frequencies. A high goodness of fit correlates with better speech understanding and user satisfaction. Fitting software shows fit diagrams in real time and allows fine-tuning. Regular checks ensure long-term accuracy of fit.

In group audiometry, several test subjects are tested at the same time, usually during preventive hearing checks in companies. Standardized signals are presented via loudspeakers in an open field and individual reactions are recorded by hand signals. This method is efficient, but less precise than single-tone audiometry. Deviating results are checked in individual tests.

A rubber membrane in the earmold ensures a tight fit and optimizes sound transmission in hearing aids. It prevents feedback and filters out ambient noise. The choice of material influences comfort and durability; medical silicone is standard. Regular replacement prevents cracking and leaks.