Reverberation refers to the delayed echo of sound in a room caused by reflections from walls, ceilings, and furnishings. The reverberation time (RT60) is the time it takes for the sound pressure to decrease by 60 dB and influences speech intelligibility and sound quality in rooms. Excessively long reverberation times obscure speech signals and make understanding difficult, while excessively short reverberation times create a "dead" sound. In sound reinforcement and room acoustics planning, materials and geometries are selected to create balanced reverberation behavior. Hearing aid users benefit from optimized reverberation control, as it reduces the burden on central speech processing.

Post-amplification is an adaptive amplification measure in hearing aids that reacts to recognized speech signals with a time delay in order to emphasize quiet passages. Unlike real-time compression, it intervenes retrospectively when speech energy falls below the comfort threshold. This improves speech comprehension in dynamic situations without unintentionally amplifying loud impulses. Parameters such as delay time and amplification strength are individually adjusted to the hearing profile. Clinical studies show that post-amplification is particularly beneficial in situations where volume changes occur rapidly.

Proximity hearing loss describes the decreasing ability to hear soft sounds as the distance from the sound source increases. It is based on the free sound propagation law (distance law), which states that sound pressure decreases by 6 dB for every doubling of distance. People with hearing loss are more affected by this effect because their need for amplification of soft signals increases. In audiology, proximity hearing loss is used to calibrate hearing aid amplification for different distances. Room acoustic measures and near-field microphones can compensate for the effect.

Near-field communication (NFC) is a wireless radio technology in the high-frequency range (13.56 MHz) that operates over short distances of a few centimeters. In hearing care, NFC is used to configure hearing aids via smartphone or tablet and to switch programs. The technology enables secure pairing without visible cables and saves battery power thanks to short transmission distances. Fitting apps use NFC to transfer real data from audiograms and filter settings. NFC increases user-friendliness and autonomy in hearing aid management.

Nerve fiber latency refers to the time it takes for an action potential to travel along an afferent auditory pathway from the inner ear to the brainstem. It depends on fiber diameter, myelination, and temperature. Delays in the millisecond range are normal and are documented in ABR measurements. Prolonged latencies indicate demyelination, inflammation, or tumors along the auditory pathway. Accurate measurement of nerve fiber delay helps to locate lesions and monitor the course of therapy.

Neural hearing refers to the central processing of acoustic signals in the brainstem and cortex, beyond the peripheral hair cell function. It includes functions such as time and level difference evaluation, pattern recognition, and speech interpretation. Even with an intact ear, neural hearing can be impaired (e.g., central auditory processing disorder), which manifests itself in a normal audiogram but poor speech comprehension. Test procedures such as dichotic listening and evoked potentials examine neural processing levels. Rehabilitation aims at neural plasticity through auditory training and cognitive therapies.

Vestibular neuritis is an inflammatory lesion of the vestibular part of the VIII cranial nerve, usually caused by a virus. It causes sudden onset of severe vertigo, nausea, and unsteadiness, without primary hearing loss. Vestibular function tests (caloric, VEMP) show ipsilateral deficits. Treatment includes corticosteroids, vestibular rehabilitation, and symptomatic medication. The prognosis is usually favorable, as central compensation mechanisms restore balance in the long term.

A neurinoma is a tumorous growth of nerve cells in the brain or nerve tissue, rarely in the auditory system. In the cerebellopontine angle, neurinomas of the VIII cranial nerve (acoustic neuroma) can be referred to as neurinomas. They compress the auditory and vestibular nerves and lead to unilateral hearing loss, tinnitus, and vertigo. Diagnosis is made by MRI with contrast medium, and treatment is by microsurgical resection or stereotactic radiotherapy. Early detection improves preservation of nerve function and quality of life.

Neuroplasticity is the ability of the nervous system to adapt structurally and functionally to changed stimuli or damage. In the auditory system, it manifests itself after hearing loss or cochlear implantation through the reorganization of cortical areas. Targeted auditory training and rehabilitation promote plastic processes and improve speech comprehension. Plastic changes can be documented using imaging techniques (fMRI). Plasticity is a prerequisite for successful auditory rehabilitation, but it decreases with age.

Neurotoxicity refers to damage to nerve tissue caused by chemical substances, including ototoxins such as aminoglycosides, cisplatin, or solvents. In the ear, these substances cause damage to hair cells, synapse loss, and neuronal degeneration. Early detection is achieved through otoacoustic emissions and ABR monitoring during therapy. Protective strategies include dose reduction, ototoxicity-protective adjuvants, and regular hearing checks. Long-term effects range from tinnitus to irreversible sensorineural hearing loss.

Nonlinear distortions occur when a system processes sound signals disproportionately to the input signal, generating harmonics and intermodulation products. In hearing aids, they can impair sound fidelity and speech comprehension if amplifier stages or transducers are not operating optimally. Total harmonic distortion measurements quantify the degree of nonlinear distortion and assist in the selection and calibration of hearing systems. Digital signal processors use linear pre-equalization and feedback suppression to minimize distortion. Severe distortion can also increase neurological processing effort and promote listener fatigue.

Noise cancellation is an active technique for suppressing ambient noise, in which a microphone picks up the interference signal, inverts it in real time, and mixes it with the useful signal. The result is that annoying low-frequency and constant noises—such as aircraft noise or air conditioning hum—are effectively reduced. In hearing aids and headphones, noise cancellation improves speech comprehension in noisy environments and reduces listening effort. Adaptive algorithms continuously adjust the filter settings to changing noise levels. Disadvantages may include a slightly reduced spatial hearing impression and battery consumption.

A noiser is an integrated tinnitus masker in modern hearing aids that emits a soft noise signal to mask ear noises and promote habituation. The spectrum and volume of the noiser can be individually adjusted to the wearer's tinnitus characteristics. Continuous, pleasant noise reduces the focus on tinnitus and alleviates cognitive stress. Noiser programs can be activated manually or controlled automatically by sound detection. Clinical studies show that integrated noiser functions significantly improve sleep quality and quality of life for tinnitus patients.

The nomenclature of audiological tests includes standardized terms for procedures such as tone, speech, otoacoustic emissions (OAE), and evoked potentials (ABR, CAEP). Uniform terminology facilitates communication between audiologists, ENT doctors, and researchers. It clearly defines test parameters such as frequency range, level, masking, and stimulus type. International standards (ISO, IEC) and professional associations publish guidelines on correct nomenclature. Consistent naming ensures the reproducibility and comparability of test results.

Normal hearing refers to hearing thresholds within the reference limits of 0 to 20 dB HL across the frequency spectrum from 125 Hz to 8 kHz. People with normal hearing can reliably perceive speech and everyday sounds without technical aids. Audiometric tests confirm normal hearing through symmetrical air and bone conduction curves without significant threshold deviations. Even with normal hearing, subtle central auditory processing problems (e.g., hidden hearing loss) can occur. The term serves as a starting point for classifying degrees of hearing loss and making decisions about treatment.

The norm curve in the audiogram is the standardized line that represents the normal hearing threshold across frequencies and serves as a comparative reference. Deviations of the measured threshold curve from this line indicate the degree and pattern of hearing loss. Norm curves are based on population surveys and reference levels according to ISO and ANSI standards. In the fitting software, the norm curve visualizes target amplification profiles for hearing aids. Audiologists use the deviations to determine individual audiogram comparisons and fitting goals.

The standard threshold is the reference level (0 dB HL) defined in audiology for the minimum audible sound pressure amplitude under standard conditions. It varies slightly with test frequency, but is internationally standardized to ensure comparability of test results. Values above the standard threshold define the degrees of hearing loss. The normal threshold is the basis for calibrating audiometers and hearing system parameters. It also serves as a reference value in otoacoustic emission tests and evoked potentials.

The cochlear nucleus is the first central switching station of the auditory pathway in the brainstem, where fibers of the vestibulocochlear nerve terminate. It is divided into ventral and dorsal nucleus complexes, which handle different aspects of acoustic signal processing, such as temporal fine structure and spectral information. From here, neurons travel on to the superior olive complex, lateral lemniscus, and subsequent auditory centers. Lesions in the cochlear nucleus lead to central auditory processing disorders despite intact peripheral function. Intraoperative evoked potentials (BERA) measure the integrity of the cochlear nucleus and its connections.

The frequency of hearing aid use describes how often and in what situations wearers use their hearing systems. Optimal use (daily, several hours) correlates strongly with treatment success, speech comprehension, and quality of life. Audiologists record usage patterns using questionnaires, wear time tracking in the device, and smart app statistics. Common barriers include stigma, handling problems, and limited comfort. Interventions such as training programs and individualized adjustments significantly increase acceptance of use.

Nystagmus is an involuntary, rhythmic eye movement pattern, often in response to vestibular stimuli or neural lesions. It can be spontaneous, positional, or caloric, and can vary in direction and speed. The analysis of nystagmus characteristics (e.g., direction, latency, decay time) provides differentiated information about peripheral and central vestibular pathologies. Video nystagmography (VNG) and Frenzel glasses are standard diagnostic tools. Therapeutically, vestibular rehabilitation and pharmacological interventions aim to reduce pathological nystagmus patterns.