Hypersensitivity in an acoustic context describes an increased perception of loudness in which even normal everyday noises are experienced as unpleasant or painful. It can be the result of hyperacusis, but can also occur temporarily after exposure to noise or stress-related central modifications. Discomfort thresholds (UCL) are determined to quantify the degree of hypersensitivity. Therapeutic approaches include gradual desensitization with controlled noise stimuli and cognitive behavioral therapy to reduce emotional distress. In hearing aid fitting, compression is carefully adjusted so as not to increase hypersensitivity.

A hearing transmission disorder refers to any functional impairment in which sound does not reach the inner ear efficiently through air conduction or bone conduction. Causes include cerumen plugs, eardrum perforations or ossicular fixations such as otosclerosis. Clinically, the audiogram shows a spread between normal bone and increased air conduction thresholds. Treatment depends on the cause: surgical reconstruction, removal of obstructions or use of bone conduction hearing systems. Regular tympanometry and otoscopy monitor the success of the treatment.

Auditory adaptation is the decrease in the perception of loudness with continuous or repeated sound stimulation in order to protect the auditory system from continuous overstimulation. It manifests itself as an increase in the hearing threshold for continued continuous tones or noise over time. Adaptation mechanisms take place in hair cells, cochlear synapses and central auditory pathways. In hearing aid technology, adaptive compression algorithms are developed to mimic these natural processes in order to maintain sound constancy. Missing or slowed adaptation can lead to fatigue and discomfort.

Uditoric fatigue refers to the temporary reduction in the perception of loudness and hearing acuity after prolonged exposure to sound, particularly at high levels. It manifests itself in increased hearing thresholds and reduced discrimination ability, which recover after periods of rest. The mechanisms lie in hair cell fatigue, synaptic exhaustion and central adaptation processes. Audiologically, fatigue is quantified with tests before and after noise exposure in order to determine risk limits for hearing protection. Rehabilitation through staggered hearing breaks and programmed "recovery noise" supports regeneration.

Auditory filtering describes the ability of the auditory system to separate relevant sound components (e.g. speech) from background noise based on frequency, time and spatial cues. Basilar membrane, receptor and neuronal filters act in the cochlea to emphasize or attenuate certain frequency bands. Central filter mechanisms in the auditory pathway and cortex select signals according to meaning and context. In hearing aids, this is technically simulated by multi-band filters, noise suppression and directional microphones. Efficient filtering improves speech comprehension in noisy environments and reduces cognitive strain.

Uditoric localization is the ability to determine the direction and distance of a sound source. It is based on interaural time differences (ITD) and level differences (ILD), as well as spectral filter effects of the pinna and head-torso transfer functions. Central processing centers in the brainstem (olive complex) combine these cues to realize spatial hearing. Damage to binaural signal processing leads to localization restrictions and reduced situational awareness. Hearing systems with binaural networking support natural localization by receiving cues synchronously.

Uditoric masking describes the phenomenon that loud sounds cover quiet sounds of the same or neighboring frequencies and prevent their perception. Internally, this creates critical bands in which masking energy is particularly effective. Masking is used in audiometry as a diagnostic tool and in hearing aids for tinnitus masking or noise suppression. Adaptive masking filters take into account individual critical bandwidths for effective noise suppression. Psychoacoustic masking effects are fundamental to compression and noise management algorithms.

Uditoric plasticity is the ability of the auditory system to adapt structurally and functionally to changes in acoustic stimuli or hearing loss. It includes new synapse formation, cortex reorganization and altered auditory pathway connections. Plasticity enables recovery after hearing loss, adaptation to hearing aids and cochlear implants and learning new hearing strategies. Rehabilitation training and musical listening promote plastic processes and improve speech comprehension and sound perception. Plasticity decreases with age, which is why early intervention is recommended.

The auditory threshold is the minimum perceptible sound pressure level for a stimulus at a given frequency and duration. It is documented in the audiogram as the hearing threshold for sounds (dB HL) and forms the basic diagnosis for hearing loss. Shifts in the threshold by more than 20 dB from the norm indicate hearing loss. Different types of thresholds - absolute, terminal and discomfort thresholds - characterize the overall dynamic hearing experience. Repeated threshold measurements make it possible to monitor the progress of therapy or noise protection measures.

Auditory processing encompasses all central neural mechanisms that transform and interpret acoustic signals from the cochlea to the cortex. It includes temporal and spectral analysis, pattern recognition and speech comprehension. Processing disorders - such as central auditory processing disorders - lead to comprehension difficulties despite normal peripheral function. Diagnostic procedures such as evoked potentials and dichotic tests check the processing levels. Rehabilitation through auditory training uses plastic adaptation to strengthen deficient processing components.

Auditory perception refers to the conscious experience of sound characteristics such as volume, pitch, timbre and spatial location. It arises through the integration of peripheral stimuli and cognitive processes in the auditory cortex and associated areas. Perceptual phenomena such as gestalt formation (auditory scene analysis) and attention control determine which sound sources are in focus. Perception is measured psychophysically using threshold and discrimination tests. Impairments can be seen in tinnitus, hidden hearing loss or central disorders and require targeted training.

Ultra-high frequencies are sound frequencies above the human hearing range (>20 kHz). Although not consciously audible, they can generate resonances and non-linear effects in external and internal acoustics. In otoacoustics, ultra-high frequency emissions (up to 100 kHz) are used to test external hair cell functions with high resolution. Ultrasound in the hearing range is used in medicine (Doppler sonography) and materials testing, but not for conventional hearing tests. Research is investigating the possible biological effects of ultra-high frequencies in hearing aids and environmental noise.

Ambient noise refers to all acoustic signals in the environment that are not part of the target stimulus, such as traffic noise, conversations or machine operation. They influence speech comprehension, hearing fatigue and the performance of hearing aids. Audiologists measure signal-to-noise ratios (SNR) in typical everyday situations in order to optimize fitting concepts. Noise reduction algorithms and directional microphones in hearing systems reduce disturbing ambient noise. In spatial planning, noise maps and acoustic simulations are used to control ambient noise levels.

The uncomfortable level (UCL) is the sound pressure level above which a sound is perceived as unpleasant or painful. It is typically 80-100 dB HL above the hearing threshold and varies individually with frequency and hearing status. UCL measurements are important for setting the maximum output power of hearing aids in order to avoid over-amplification. Deviations may indicate hyperacusis or central auditory dysregulation. Progress checks of the UCL help to adjust comfort parameters according to the situation.

The just-noticeable difference (JND) is the smallest perceptible difference of an acoustic stimulus, e.g. in volume or frequency. It is determined using methods such as the two-way comparison method and is dependent on frequency and level. Typical loudness JNDs are around 1 dB, frequency JNDs are 0.2-1 % of the carrier frequency. In hearing aids, JND values are used to fine-tune compression and filter bandwidths. Increased JNDs indicate reduced resolution and can explain speech understanding problems.