The damping factor is the ratio of coupled energy to emitted energy in an oscillating system. In the middle ear, it provides information about how elastically the ossicular chain vibrates and how much vibration energy it absorbs. Low damping factors indicate excessive reflections, while high damping factors indicate significant energy losses. Audiometrically, a change in damping can indicate otosclerosis or loosening of implants.

The damping coefficient quantifies how quickly sound waves lose amplitude in a material or medium. In the cochlea, it influences how vibrations decay along the basilar membrane, thus shaping the frequency resolution. In building and room acoustics, it defines how much sound is absorbed by walls or ceilings. Hearing aid manufacturers take material damping into account in earmolds to minimize resonance.

Dehiscence of the semicircular canal is a bony gap in the roof of a semicircular canal, usually in the superior canal. This opening leads to abnormal irritation of the cupula and causes symptoms such as autophonic noise, dizziness when pressure changes, and hearing loss. The diagnosis is made by CT scan and vestibular function tests. Surgical closure of the dehiscence can significantly alleviate symptoms.

Decompensation refers to the failure of hearing aids or central processing processes when hearing loss is so severe that compensatory mechanisms are no longer sufficient. Those affected suddenly find that their usual hearing aid programs are no longer adequate and report significant difficulties in understanding. This condition requires a reassessment of the treatment, often with stronger amplification or a cochlear implant. Rapid adjustment reduces stress and social isolation.

Auditory deprivation occurs when the brain receives no or only greatly reduced acoustic stimuli over a long period of time. This leads to the degeneration of central auditory networks and impaired speech comprehension, even if peripheral hearing is later restored. Early hearing care for children is essential to prevent deprivation and ensure normal speech development. Rehabilitation includes intensive hearing training to promote neural plasticity.

Desensitization aims to reduce hypersensitivity to tinnitus noises by exposing sufferers to controlled noise or music stimuli. Through regular, controlled exposure, the brain becomes accustomed to the noise and increasingly filters it out. Psychological methods such as cognitive behavioral therapy complement auditory training. Long-term studies show a sustained reduction in tinnitus stress and an improved quality of life.

Detection refers to the process by which the ear can just about perceive a sound at a certain sound pressure level. The detection threshold is determined in a quiet room using tone audiometry and forms the hearing curve in the audiogram. It serves as the basis for defining normal hearing and degrees of hearing loss. Variations in detection performance provide information about peripheral and central hearing disorders.

The decibel (dB) is a logarithmic unit used to indicate level ratios, often sound pressure or sound intensity. An increase of 10 dB corresponds to approximately a doubling of the perceived volume. In audiology, hearing thresholds are specified relative to a standard (0 dB HL). Decibel values help to define noise exposure limits and calibrate hearing aid amplifications.

Diagnostic audiometry encompasses all tests that determine the type and extent of hearing loss, including tone, speech, and impedance measurements. It differentiates between conductive and sensorineural hearing loss as well as central disorders. The results serve as the basis for treatment decisions such as hearing aid fitting or surgical intervention. Modern computer-assisted audiometers deliver precise, reproducible findings.

In dichotic listening, different acoustic signals are fed to each ear simultaneously to test central processing and lateralization. Typical tests present competing speech or tone sequences to assess attention and filtering ability. Disturbances are evident in central auditory processing disorders or after strokes. Dichotic paradigms are used in pediatric audiology diagnostics and neurorehabilitation.

Differential tone audiometry measures the ability to detect very small frequency differences between two tones. Test subjects indicate which tone sounds higher or lower, allowing the frequency resolution of the ear to be quantified. Reduced differentiation ability indicates central or cochlear disorders. The method provides insights into neural sharpening and plasticity of the auditory system.

Digital hearing aids convert acoustic signals into digital data, process them using algorithms, and convert them back into sound. They offer adaptive noise reduction, feedback management, and multi-channel compression. Software-based fine-tuning allows for individual sound profiles for different listening situations. Compared to analog devices, they provide better speech comprehension and greater flexibility.

Discrimination refers to the ability to perceive two similar acoustic stimuli as different, such as differences in pitch or volume. It is tested in speech and tone audiometry and is crucial for speech comprehension. Impaired discrimination is found in cochlear dead zones and central processing disorders. Training programs aim to improve discrimination thresholds.

Distance hearing describes the perception of sound sources that are far away from the listener. Sound pressure levels decrease with increasing distance, which is why the ear and hearing systems must be sensitive to quiet signals. In room acoustics and sound reinforcement technology, loudspeaker positions and reverberation time are optimized to facilitate distance hearing. In cases of hearing loss, distance hearing deteriorates more than near hearing, which requires special amplification strategies.

A distortion product OAE is a feedback emission generated by the cochlea when two tones are present simultaneously and the nonlinear properties of the hair cells produce distortion products. These emissions are measured in the ear canal and provide information about the function of the outer hair cells. The presence of DPOAE indicates intact cochlear amplifiers, while their absence indicates damage. DPOAE tests are quick, objective, and are also used on newborns.

Distortion products arise in nonlinear systems when two or more frequencies are mixed and generate new frequencies (sum/difference). In the ear, they are produced by the active amplification of the outer hair cells. They can be used diagnostically as otoacoustic emissions and indicate cochlear health. In electrobiology, they are used as an indicator of system linearity and filter quality.

DPOAE refers to the measurement of specific distortion products generated by the cochlea in response to two test tones. It allows non-invasive assessment of outer hair cell function without active participation by the patient. DPOAE is considered the standard in newborn hearing screening and early ototoxicity diagnostics. Absent DPOAE with a normal tympanogram indicates sensorineural hearing loss.

Pressure equalization between the middle ear and the surrounding environment occurs via the Eustachian tube, ensuring that the eardrum can vibrate freely. Malfunctions lead to underpressure or overpressure, causing pain and hearing loss. Techniques such as the Valsalva maneuver or tube catheters are used to treat tubal dysfunction. Tympanometry documents the pressure curve and helps in the decision-making process for ear tubes.

A feeling of pressure occurs when the pressure in the middle ear differs from the external and internal pressure, usually during air travel or when you have a cold. The eardrum tightens and mechanical sound conduction deteriorates. Repeated ventilation exercises activate the Eustachian tube and equalize the pressure. A persistent feeling of pressure may indicate Eustachian tube dysfunction or middle ear effusion.

Pressure pain in the ear indicates inflammatory processes such as otitis media or exostoses. Palpation of the tragus and percussion of the mastoid area cause pain in the event of pathological changes. The severity of pain often correlates with the degree of inflammation and the amount of effusion. Pain therapy combines analgesics with targeted treatment of the underlying disease.

The dynamic range refers to the difference between the hearing threshold and the pain threshold of the ear. It typically ranges from 0 dB HL to approximately 120 dB SPL. Hearing aids must cover this range without producing distortion. A reduced dynamic range due to hearing loss requires compression to attenuate loud sounds and make soft sounds audible.

Dynamic compression in hearing aids reduces the difference in volume between quiet and loud signals by attenuating loud sounds more strongly. This makes ambient noise tolerable and quiet speech audible. Compression parameters such as ratio and attack and release times are set individually. However, excessive compression can impair sound quality and speech intelligibility.

Dysacusis describes impaired sound quality despite preserved hearing ability, such as distortion or blurring in the speech signal. Those affected hear sounds but cannot distinguish them clearly. The causes are usually cochlear nonlinearities or central processing deficits. Treatment includes targeted hearing training and adjustment of signal processing in the hearing aid.

Eustachian tube dysfunction occurs when the Eustachian tube does not open and close properly, leading to pressure build-up and fluid accumulation in the middle ear. Symptoms include a feeling of pressure, hearing loss, and recurrent infections. Diagnosis is made using tympanometry and a tube function test. Treatment ranges from nasal drops and balloon dilation to ear tube implantation.