Glossary on hearing and hearing loss

Echolocation is the active detection of objects by emitting sound pulses and evaluating the returning echoes. Bats and some marine mammals use this method to navigate in the dark or in murky water and to find prey. Humans can train themselves to use echolocation, for example blind people who use it to derive spatial information acoustically. Neurobiological studies show that this involves a plastic reorganization of the auditory areas of the brain. Technical applications adapt this principle for sonar and ultrasound devices in medicine and industry.

Intrinsic sensitivity refers to the minimum signal that a measuring device or hearing system can reliably detect from its own noise. In hearing aids, it corresponds to the internal microphone and amplification noise, which is considered the lower limit for amplification. A low value is important so that quiet environmental sounds are not masked by inherent noise. Manufacturers optimize electronic components and filter algorithms to reduce inherent sensitivity. In measurement technology, the noise floor is reported as a key figure.

Intrinsic noise is the continuous background noise of electronic systems in the absence of an input signal. In hearing aids, it can impair the perception of very soft sounds and reduce wearing comfort. The level of intrinsic noise depends on circuit topology, component quality, and filter design. Modern digital hearing aids use noise reduction algorithms to actively minimize self-noise. Regular maintenance and cleaning of the microphones also help to prevent extraneous noise.

Acoustic sleep aids such as white noise, ocean sounds, or soft piano music promote falling asleep and staying asleep by masking disturbing ambient noises. People with tinnitus in particular benefit from continuous sound patterns that divert attention away from the noise in their ears. Studies show that such sounds shorten sleep latency and improve sleep quality. Apps and hearing aid programs offer customizable sound profiles and timer functions. It is important to keep the volume below 40 dB so as not to put additional strain on the ears.

The transient response describes the initial reaction of an oscillating system to a sudden sound stimulus before a steady state is reached. In the ear, this affects the eardrum and ossicular chain, which initially oscillate excessively before reaching stable amplitudes. Audiometric impedance measurements use the transient response to detect middle ear pathologies such as otosclerosis or tube closure. Abnormal transient times indicate changes in the stiffness or mass of the structures. In hearing aid technology, the transient response of filters is optimized to minimize distortion during rapid level changes.

The adjustment range of a hearing aid defines the level range that the device can process and amplify without distortion. It ranges from the minimum input volume at which amplification still occurs to the maximum volume at which compression begins. A large adjustment range allows very quiet and loud signals to be heard without clipping or discomfort. Audiologists select a device with a suitable range based on the individual's hearing loss profile. Technical data sheets specify the adjustment range together with the compression ratio and amplification factors.

Single-frequency analysis breaks down complex sound signals into their individual frequency components using Fourier transformation. It provides amplitude- and phase-specific information on each frequency component and forms the basis for spectral analysis in audiology. Applications include the analysis of otoacoustic emissions, room acoustics measurements, and hearing aid fine-tuning. Diagrams show level curves across the frequency spectrum and allow conclusions to be drawn about filter behavior and cochlear function. In research, single frequency analysis is used to investigate neural response patterns in the auditory system.

In pure tone audiometry, tones of individual frequencies and levels are presented one after the other to determine the hearing threshold for each frequency. The results are visualized in the audiogram as air conduction and bone conduction curves. This procedure is standard in the diagnosis of conductive and sensorineural hearing loss. Modern audiometers offer automated test protocols and adaptive procedures for faster, more reliable measurements. Validity depends on the cooperation and reaction time of the test subject.

Electrocochleography measures electrical potentials in the inner ear and auditory nerve in response to acoustic stimuli. A needle electrode on the eardrum or an ear canal electrode is used to record the summation potential and endolymphatic pressure. ECochG is used to diagnose Meniere's disease, endolymphatic hydrops, and acoustic trauma. Peak pressure amplitudes correlate with the severity of the hydrops. The examination is minimally invasive and provides important data on the inner ear mechanics.

The sensitivity range refers to the level range in which the human ear or a hearing system can process acoustic stimuli without distortion. For the human ear, this range lies between the hearing threshold (0 dB HL) and the pain threshold (~120 dB SPL). Hearing aids use compression to adapt this range to the residual hearing in order to soften loud noises and make quiet ones audible. Measurement systems calibrate the sensitivity range to ensure linear response within this window.

The perception threshold is the lowest sound pressure level that can just be perceived by the ear. It is determined separately for each test frequency in audiometry and documented in the audiogram. Deviations from standard values define the degree of hearing loss. Together with the pain threshold, the perception threshold forms the dynamic range of hearing. Clinically, it helps to distinguish between sound conduction and sound perception disorders.

Endolymph is the potassium-rich fluid in the cochlear duct and the membranous semicircular canals. It transmits mechanical vibrations to hair cells and generates electrochemical signals. A pressure disturbance in the endolymph, as in endolymphatic hydrops, leads to vertigo and hearing loss. Laboratory measurements and clinical tests of endolymph function support the diagnosis of Meniere's disease. Research focuses on regulating endolymph volume for the treatment of vestibular disorders.

Energy measurement integrates sound levels over time and frequency to assess cumulative noise exposure. It forms the basis for occupational noise protection guidelines that define maximum daily doses. Devices continuously record level values and calculate daily exposure values (LEX,8h). Epidemiological studies correlate energy exposure with the risk of hearing loss. Preventive measures are based on energy measurements to reduce noise damage.

Relaxing sounds such as white noise, ocean waves, or gentle melodies mask disturbing noises in the ear and promote sleep and stress reduction. For tinnitus patients, they reduce focus on the noise in the ear and improve quality of life. Clinical studies show that controlled sound exposure reduces anxiety and sleep latency. Apps and hearing aid programs offer personalized sound libraries. It is important to keep levels below 40 dB to avoid additional hearing stress.

The extended high-frequency range covers frequencies above 8 kHz to around 16 kHz and contributes to timbre and music perception. Early detection of high-frequency loss serves as an early indicator of noise-induced hearing loss. High-frequency audiometry tests this range to detect subtle deficits. Hearing aids with high-frequency amplification improve music and speech intelligibility in complex sound environments.

The Eustachian tube connects the middle ear and nasopharynx, regulates pressure equalization, and protects against nasal secretions. It opens when swallowing or yawning and closes passively to ensure middle ear ventilation. Dysfunctions lead to pressure sensations, hearing loss, and effusions. Balloon dilation and nasal corticosteroids are established therapies. Functional tests measure opening pressure and duration.

Evoked potentials are electrical responses of the auditory system to sound stimuli, measured using scalp electrodes. They are divided into ABR (brainstem), MLR (mid-latency), and CAEP (cortical). These objective tests check the integrity of the auditory pathway without active participation. Used in newborn screening, neurological diagnostics, and CI fitting. Analysis of latency and amplitude provides information about the location of lesions.

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