The labyrinth in the inner ear consists of the bony and membranous parts and includes the cochlea, vestibule and semicircular canals. It is used for both sound transduction (cochlea) and balance perception (vestibular organ). The spaces filled with endolymph transmit mechanical stimuli to hair cells, which convert them into electrical signals. Diseases such as labyrinthitis or Menière's disease lead to dizziness, nausea and hearing loss. Imaging procedures and functional tests (caloric, VEMP) examine the integrity of the labyrinth.

Labyrinthitis is an inflammation of the inner ear, typically viral or bacterial, and affects both the hearing and vestibular organs. Symptoms include acute rotary vertigo, nausea, vomiting and often unilateral hearing loss or tinnitus. Diagnostics include audiometry, vestibular function tests and, if necessary, MRI to rule out other causes. Treatment combines antiviral or antibiotic medication with corticosteroids and vestibular rehabilitation training. Vestibular function usually recovers partially, residual damage can leave persistent dizziness or hearing loss.

Noise exposure refers to the exposure to harmful or disturbing sound levels in the environment and at work. It is measured in dB A and weighted over time (e.g. LEX,8h). Chronic noise exposure leads to stress, sleep disorders and occupational hearing loss. National and international guidelines set limits for industrial, traffic and leisure noise. Preventive measures include noise barriers, hearing protection and quiet zones in cities.

A noise indicator is a key figure that quantifies noise exposure, e.g. Lden (day-evening-night), Lnight or Lday. It integrates levels and time components in order to estimate health risks. Municipal noise maps use indicators to depict pollution hotspots and plan protective measures. Specific indicators such as LEX,8h apply to workplaces. Indicators are the basis for noise action plans and environmental reporting.

A noise level meter is a measuring device that records sound pressure levels in real time and evaluates them in dB. Professional Class 1 and Class 2 meters meet standards (IEC 61672) for precision and frequency weighting (A and C filters). They are used in occupational safety, environmental monitoring and room acoustics. Calibration with external calibrators ensures measurement accuracy. Mobile versions and apps offer simple indicators, but do not achieve laboratory quality.

Noise protection includes technical, structural and organizational measures to dampen sound sources or minimize sound propagation. Examples include noise barriers, absorbent materials and traffic calming. Personal hearing protection (earplugs, earmuffs) supplements structural protection. In buildings, standards regulate minimum requirements for sound insulation. Effective noise protection improves the quality of living and working conditions and prevents hearing damage.

Noise protection ordinances are legal regulations at national or EU level that define limit values and procedures for noise monitoring. They define permissible levels in industrial, traffic and residential areas as well as night and day times. Residents can file noise complaints and enforce measures such as speed limits or noise barriers. Local authorities draw up noise action plans based on ordinances. Violations are punished with fines.

Noise-induced hearing loss is an occupational disease caused by chronic exposure to noise, which leads to sensorineural hearing loss, particularly in the high frequency range. It manifests itself as "cracking" and a falling audiogram curve from 3 kHz. Prevention through hearing protection and regular preventive audiometry is required by law. The patient is fitted with hearing aids that specifically compensate for high-frequency loss. Rehabilitation includes hearing training and workplace-related adjustments.

Noise prevention aims to minimize noise pollution before it causes damage to health. It includes risk assessment, planning protective measures and informing those affected. Technical precautions include quieter machines, structural insulation and traffic control. Personal precautions include hearing protection and rules of conduct. Monitoring and regular measurements ensure the effectiveness of the measures.

Auditory latency is the time span between sound stimulus and measurable reaction in the auditory system, e.g. evoked potentials or conscious perception. Latencies provide information about the functional state of peripheral and central auditory pathways. Prolonged latencies indicate demyelination, tumours or neuropathic damage. In hearing aids, signal processing latency is minimized to ensure audio-video synchrony. Standard values exist for ABR, MLR and CAEP components.

Lateral inhibition is a neural principle in which activated neurons inhibit their neighbors to increase contrast and edge sharpness. In the auditory system, it improves frequency selectivity by attenuating neighboring frequency channels. This leads to clearer understanding of sound and speech, especially in complex sound environments. Disturbances in lateral inhibition can cause wider sound fields and poorer discrimination. Modeling of this effect is incorporated into hearing aid filter designs.

Laterization is the apparent perception that a sound source is to the left or right of the center of the body, based on interaural time differences (ITD) and interaural level differences (ILD). The brain compares minimal time differences and volume differences between the two ears to determine direction. Laterization is essential for spatial hearing and situational orientation, for example in road traffic. When fitting hearing aids, it is ensured that binaural synchronization is maintained so that laterization is not distorted. Tests in the sound field measure laterization accuracy and help to detect processing disorders.

Loudness is the subjective auditory perception of the strength of a sound, which does not correlate linearly with the sound pressure level (dB SPL). Psychoacoustic models such as the Zwicker model describe how frequency and level together determine the perceived loudness in sone. Loudness scales (see below) standardize this perception for technical applications and hearing aid fitting. Loudness depends on context, duration and frequency spectrum; different loudnesses can be perceived at the same level. Hearing aid compression optimizes the perception of loudness by amplifying soft sounds and attenuating loud ones.

In loudness scaling, test subjects subjectively rate the perceived loudness of test signals on a numerical or verbal scale. Methods such as category scaling or magnitude estimation provide functions that convert sound pressure into loudness (sone). These functions are used to calibrate hearing aids to ensure the desired loudness experience. Differences in scaling indicate individual loudness sensitivity and hyperacusis tendencies. Standardized scales (DIN 45631) ensure comparability between examinations.

Loudspeakers convert electrical audio signals into sound waves and are central components in free-field audiometry and sound reinforcement systems. Important parameters are frequency response, distortion factor and directivity. Calibrated studio monitors deliver precise levels for listening tests, while consumer loudspeakers are optimized for sound aesthetics. In listening studies, coaxial or dipole loudspeakers are often used to minimize reflections. Speaker placement in the room influences reverberation and listening comfort and is planned acoustically.

Quality of life with hearing loss encompasses physical, psychological and social dimensions, including communication skills, self-esteem and social participation. Hearing loss increases the risk of isolation, depression and cognitive impairment. Instruments such as HHIE ("Hearing Handicap Inventory for the Elderly") quantify subjective burden. Interventions (hearing aids, rehabilitation, psychosocial support) aim to improve all areas of quality of life. Long-term studies show that early care significantly improves quality of life.

The line impedance is the complex resistance of an acoustic path, e.g. middle ear or audio cable, to sound or signal transmission. It is made up of resistive and reactive components and varies depending on the frequency. In tympanometry, middle ear impedance is measured in order to assess the ability to vibrate and the ossicular chain. Deviations indicate stiffening (otosclerosis) or fluid accumulation. In hearing aid technology, impedance matching is used to ensure maximum performance and minimum reflections.

An auditory lexicon is the mental representation of sound patterns, words and their meanings stored in the brain. It enables rapid word recognition and speech comprehension by comparing acoustic input with stored entries. Models of language processing differentiate between the phonological and semantic lexicon. Disorders, such as aphasia or central auditory processing disorders, impair access to the lexicon. In rehabilitation, lexicon access is trained through speech exercises and auditory training.

Lip reading is the technique of visually decoding spoken sounds and words based on the movement of the lips, jaw and facial muscles. It helps people with hearing impairments to improve their understanding of speech in quiet and noisy environments. In addition to visual training, successful lipreading also requires knowledge of phonetics and speech rhythms. In practice, those affected combine lip reading with hearing aids or cochlear implants to achieve maximum communication skills. Speech therapists offer systematic exercises to synchronize visual and auditory impressions.

Lip-synchronization refers to the adjustment of audio and video tracks so that lip movements and spoken sound match exactly in time. A lack of synchronization (lip sync error) disturbs speech comprehension and can lead to cognitive overload. In subtitling and for hearing aids with video streaming, precise lip synchronization is essential in order to correctly assign speech sources. Technically, the delay is measured digitally and compensated for in milliseconds. Good synchronization improves the perceived naturalness and acceptance of audiovisual content.

The logarithmic scale represents values in exponential steps so that large data ranges can be represented compactly. In audiology, the sound pressure level is measured logarithmically in decibels (dB) to represent linear hearing perception. A doubling of loudness corresponds to approximately +10 dB, which is plausible and manageable on a logarithmic scale. Audiograms and frequency responses of hearing aids use this scaling to clearly visualize hearing thresholds and amplification profiles. Logarithmic representations make it easier to compare different levels and frequency ranges.

Speech therapy in aural rehabilitation focuses on the language and communication skills of people with hearing loss. Speech therapists train articulation, pronunciation and sound comprehension using auditory-visual methods, including lip reading and sound therapy. They develop individual therapy plans to promote speech comprehension in everyday situations. They also use auditory training and cognitive strategies to compensate for central processing disorders. Close collaboration with audiologists and psychologists ensures a holistic approach to treatment.

Air conduction is the main auditory pathway in which sound waves pass through the ear canal, vibrate the eardrum and are transmitted to the inner ear via the ossicular chain. Sound and speech audiometry measure air conduction thresholds via headphones to determine the extent of hearing loss. Deviations between air and bone conduction indicate sound conduction problems or middle ear diseases. The air conduction curve in the audiogram forms the basis of every hearing diagnosis. Pathologies such as otoscopy findings are correlated with air conduction data.

An air conduction audiogram is a graphical representation of hearing thresholds over frequencies, measured by an air conduction test. It shows individual hearing curves and defines the degree of hearing loss, e.g. mild, moderate or profound. The curve distinguishes between air conduction and bone conduction to differentiate between causes of hearing loss. Standardized test frequencies range from 125 Hz to 8 kHz, and up to 16 kHz for high-frequency audiometry. Audiograms are essential for the selection and adjustment of hearing aids.

Airborne sound is sound that propagates through the air as a pressure wave and leads to hearing via the outer ear. It differs from structure-borne sound as the sound source consists of air molecule pressure fluctuations. In room acoustics, airborne sound levels, reflection and absorption are analyzed in order to optimize reverberation and reverberation. Hearing tests and noise measurements are based on airborne sound measurements with microphones. Hearing protection aims to reduce airborne sound levels to below the limits that are harmless to health.