The caloric test tests the function of the horizontal semicircular canal by introducing warm or cold water or air into the ear canal. Temperature differences generate endolymphatic currents that trigger a typical nystagmus (eye jerking movements). The intensity and direction of the nystagmus provide information about vestibular functional asymmetries and central-vestibular integrity. It is standard in the diagnosis of vertigo and helps to localize vestibular deficits on one side. As the irritation can be unpleasant, the examination is carried out under continuous monitoring of eye movements.

Canal audiometry measures the sound conduction properties of individual frequency bands ("canals") in the ear canal or hearing aid. It uses narrow filter bands to determine thresholds and amplification requirements for each channel. The results help to precisely set multi-band compression parameters and ensure clear speech understanding. In research, channel audiometry is used to investigate frequency selectivity and masking effects. Modern hearing aid fitting software visualizes canal audiograms in real time for fine calibration.

A channel compressor is a dynamic processor that controls the level compression separately in each frequency channel of a hearing aid. It reduces loud signals above the comfort threshold more than quiet signals in order to adapt the dynamic range to the residual hearing. Parameters such as ratio, attack and release time are optimized individually for each channel. Multi-channel compression makes it possible to emphasize speech components in critical bands and at the same time attenuate impulse-like noise. However, incorrectly set compressors can cause sound artifacts and discomfort.

Channel separation refers to the division of the audio spectrum into separate frequency bands for independent processing. It forms the basis for multi-band compression, filtering and noise suppression in hearing aids. Good channel separation minimizes crosstalk between adjacent bands and prevents phase problems. The number and bandwidth of the channels are adapted to the hearing loss profile and the processing power of the processor. Adaptive systems change channel boundaries according to the situation to ensure optimum sound quality in changing environments.

The number of channels indicates how many frequency bands a hearing aid divides the audio signal into. Typical values are between 4 and 16 channels; more channels allow finer adjustment, but require more computing power. A higher number of channels supports precise masking management and individual amplification profiles. However, too many channels can lead to over-matching and increased noise. The ideal number of channels depends on the hearing loss pattern and the wearer's processing capabilities.

Capsulotitis is an inflammation of the bony capsule of the inner ear, usually the result of otitis media or skull base injury. It causes severe ear pain, dizziness and often sensorineural hearing loss. CT/MRI and laboratory values are used for diagnosis to determine the extent and pathogen. Treatment includes systemic antibiotics, pain management and surgical drainage if necessary. Early treatment is essential to prevent permanent inner ear damage.

Cascade amplification refers to a multi-stage amplification architecture in which several amplifier stages are connected in series. Each stage increases the level slightly, resulting in overall amplification without strong distortion. This technique improves noise performance and linearization compared to single stages with high gain. In digital hearing aids, cascade amplification is found in both analog-to-digital converters and output amplifiers. It contributes to low inherent noise and high sound fidelity.

Sound compression reduces the dynamics of audio signals by attenuating loud sections more than quiet ones. It is indispensable in hearing aids to protect residual hearing from overmodulation and at the same time make weak signals audible. Compression parameters such as ratio, knee point and release time determine the response behavior. Adaptive compression automatically adapts to speech and ambient noise. However, incorrectly set compression can make the sound "flat" or unnatural.

The cerebellopontine angle is the anatomical space between the cerebellum and the pons through which the VIII cranial nerve passes. cranial nerve passes through. Acoustic neuromas, benign tumors that lead to hearing loss, tinnitus and dizziness, often develop here. Microsurgical resection requires access through this angle, whereby the brain stem and vessels must be spared. Intra-operative monitoring of the auditory brainstem outlets protects nerve function. Postoperative imaging monitors resection completion and complications.

Der Klirrfaktor gibt das Verhältnis der Summe aller harmonischen Obertöne zur Grundschwingung an und quantifiziert Verzerrungen in einem System. In Hörgeräten beschreibt er, wie stark das Ausgangssignal vom Eingangssignal abweicht. Niedrige Klirrfaktoren (<1 %) sind wünschenswert für unverfälschten Klang. Messungen erfolgen mit Sinus‑Sweeps und Spektralanalyse. Hoher Klirrfaktor kann Sprachverständnis und Klangqualität erheblich verschlechtern.

A blast trauma is caused by extremely short, high-intensity sound explosions that can immediately destroy hair cells and synaptic connections in the inner ear. Symptoms include sudden hearing loss, tinnitus and dizziness. Emergency treatment with high-dose corticosteroids and hyperbaric oxygenation can reduce damage, but must be given immediately. Long-term consequences include permanent hearing loss and psychological stress. Prevention through hearing protection in the event of gunshot noise or explosions is essential.

Bone conduction transmits sound directly to the cochlea by vibrating the skull, bypassing the outer ear and middle ear. It is used in audiometry to differentiate between conductive and sensorineural hearing loss. Bone conduction hearing systems are used for patients with middle ear problems. Implantable bone conduction devices (BAHS, Bonebridge) deliver higher sound quality than traditional bone conduction hearing aids. Bone conduction also plays a role in autophony.

The cochlea is the snail-shaped inner ear organ in which sound waves are converted into electrical nerve impulses. Inner and outer hair cells are located on the basilar membrane, which encode sounds of different frequencies through mechano-electrical transduction. Tonotopy ensures that high frequencies are detected at the base and low frequencies at the apex of the cochlea. Damage to the cochlea, for example through noise or ototoxins, leads to permanent sensorineural hearing loss. Research into cell regeneration and cochlear implants aims to restore function.

Communicative accessibility means that people with hearing loss have unrestricted access to linguistic content, for example through sign language, subtitles, inductive hearing systems or real-time transcription. It includes technical, architectural and organizational measures in public spaces, media and digital offerings. The aim is equal participation in education, culture and everyday life. Legal requirements demand accessibility in public facilities and online services. Audiologists and acousticians advise on suitable aids and installations.

Compensation procedures are used to compensate for hearing loss by technical or therapeutic means. They range from hearing aids and implants to hearing training and environmental adaptations. Digital signal processors use multi-band compression, noise reduction and directional microphones to amplify speech. Therapeutic compensation includes central auditory processing training to promote neural plasticity. Combination of technical and rehabilitative compensation achieves best results for speech understanding.

The compression dynamic range describes how a hearing aid reacts to different input levels: Quiet signals are amplified more than loud ones in order to make optimum use of the wearer's dynamic range. Important parameters are compression ratio, knee point and attack/release time. A fast attack time protects against impulse noise, while a slow release time preserves natural sound characteristics. Individual fine-tuning adapts dynamics to hearing loss profile and hearing preferences. Mismatching can impair speech intelligibility and sound quality.

In conductive hearing loss, the transmission of sound through the outer ear or middle ear is impaired, for example due to a cerumen plug, eardrum perforation or otosclerosis. Those affected have normal bone conduction but increased air conduction thresholds in the audiogram. Treatment options include surgical reconstruction, removal of obstructions or bone conduction hearing systems. Tympanometry and the Rinne test help to differentiate between conductive and sensorineural losses. Prognosis is usually very good with successful treatment.

The head-related transfer function (HRTF) describes how the head, auricles and torso filter sound depending on frequency and thus generate directional cues. It is essential for spatial hearing and virtual reality audio. Individual HRTFs are recorded or calculated with microphones on the ear to create realistic 3D audio effects. In hearing aid development, HRTF models are used to achieve natural localization despite the device. Adaptive algorithms can adjust HRTFs to head movements in real time.

Headphones are sound transducers that are positioned directly on the ear and transmit sound to the eardrum in an isolated manner. They are used in audiometry (everyday testing and research) and as accessories for hearing aid streamers. Closed designs offer a high level of shielding against ambient noise, while open designs have a more natural sound. Calibrated measuring headphones guarantee standardized sound levels in threshold tests. Hygiene and seating comfort are important for precise and reliable measurements.

The hair cell power law describes the non-linear relationship between the deflection of the hair cell stereocilia and the electrical response triggered. Small deflections lead to proportionally larger receptor potentials, which explains the sensitivity of the cochlear amplifier. If certain deflection limits are exceeded, the characteristic curve tilts to provide protection against overstimulation. Changes to this law due to damage influence the dynamic range and frequency resolution. Biophysical models help to optimize hearing aid compression.

A crystal calibrator generates a defined sound pressure level (usually 94 dB SPL at 1 kHz) in a closed adapter in order to test microphone sensitivities. It uses piezoelectric crystals for stable frequency and amplitude. Calibration before each measurement run ensures accuracy in audiometry and room acoustics. Regular traceability to national standards ensures measurement consistency. Documentation of calibration is part of quality control in laboratories and clinics.

The auditory short-term memory stores acoustic information for seconds to minutes in order to process speech and sounds. It enables sentences to be understood by holding previous words in memory. Disruptions lead to difficulties with longer passages of speech and complex listening situations. Tests such as dichotic number span measure auditory memory performance. Auditory training and cognitive exercises can improve short-term memory functions.