The damping factor is the ratio of coupled energy to emitted energy in a vibrating system. In the middle ear, it provides information on how elastically the ossicular chain vibrates and how strongly it absorbs vibration energy. Low attenuation factors indicate excessive reflections, high ones indicate strong energy losses. Audiometrically, a change in attenuation can indicate otosclerosis or loosening of implants.

The attenuation 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 strongly walls or ceilings absorb sound. Hearing aid manufacturers take material damping into account in earmoulds in order to minimize resonances.

Dehiscence of the semicircular canal is characterized by 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 with pressure changes and hearing loss. 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 when a hearing loss is so severe that compensation mechanisms are no longer sufficient. Those affected suddenly experience that familiar hearing aid programs are no longer sufficient and report considerable difficulties in understanding. This condition requires re-evaluation of the fitting, often with stronger amplification or cochlear implant. Rapid adaptation 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 regression 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 auditory training to promote neural plasticity.

Desensitization aims to reduce hypersensitivity to tinnitus sounds by confronting those affected with noise or music stimuli in a controlled manner. Through regular, controlled exposure, the brain becomes accustomed to the noise and increasingly blocks it out. Psychological methods such as cognitive behavioral therapy complement auditory training. Long-term studies show a lasting reduction in tinnitus stress and improved quality of life.

Detection describes the process from which sound pressure level the ear can just barely perceive a sound. The detection threshold is determined in a quiet room using sound 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 for specifying 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 amplification.

Diagnostic audiometry includes all tests that determine the type and extent of hearing loss, including sound, 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 interventions. Modern computer-aided audiometers provide precise, reproducible findings.

In dichotic listening, different acoustic signals are presented 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 seen 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 recognize very small frequency differences between two tones. Test subjects indicate which tone sounds higher or lower; this allows the frequency resolution of the ear to be quantified. Reduced differentiation ability indicates central or cochlear disorders. The method provides insights into neuronal sharpening and plasticity of the auditory system.

Digital hearing systems 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-supported fine adjustment allows individual sound profiles for different listening situations. Compared to analog devices, they provide better speech intelligibility 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. Limited discrimination is found in cochlear dead zones and central processing disorders. Training programs aim to improve discrimination thresholds.

Distance hearing describes the detection of sound sources that are far away from the listener. Sound pressure levels fall 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 times are optimized to facilitate distance hearing. With hearing loss, distance hearing deteriorates more than near hearing, which requires special amplification strategies.

A distortion product OAE is a back emission generated by the cochlea when two sounds are present at the same time and the non-linear properties of the hair cells generate distortion products. These emissions are measured in the ear canal and provide information about the function of the outer hair cells. The presence of DPOAEs indicates an intact cochlear amplifier, their absence indicates damage. DPOAE tests are fast, objective and are also used in newborns.

Distortion products arise in non-linear systems when two or more frequencies are mixed and generate new frequencies (sum/difference). In the ear, they are generated 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 the active cooperation of the patient. DPOAEs are considered standard in newborn hearing screening and early ototoxicity diagnostics. Absence of DPOAEs with a normal tympanogram indicates sensorineural hearing loss.

Pressure equalization between the middle ear and the environment takes place via the Eustachian tube and ensures that the eardrum can vibrate freely. Malfunctions lead to negative or positive pressure, which causes pain and hearing loss. Techniques such as Valsalva maneuvers or tube catheters treat tubal dysfunction. Tympanometry documents the pressure curve and helps in the decision making process for tympanostomy tubes.

A feeling of pressure occurs when the middle ear pressure differs from the external and internal pressure, usually when traveling by plane or having a cold. The eardrum stretches and mechanical sound conduction deteriorates. Repeated ventilation exercises activate the auditory tube and equalize the pressure. A persistent feeling of pressure may indicate tubal 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 relieve pain in case of pathological changes. Pain intensity 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 describes the difference between the hearing threshold and the pain threshold of the ear. It typically ranges from 0 dB HL to around 120 dB SPL. Hearing aids must cover this range without causing distortion. Reduced dynamic range in hearing loss requires compression to attenuate loud sounds and make soft sounds audible.

Dynamic compression in hearing aids reduces the difference in level between soft and loud signals by attenuating loud sounds to a greater extent. This means that ambient noise remains tolerable and quiet speech becomes audible. Compression parameters such as ratio and attack/release time are set individually. However, excessive compression can impair sound quality and speech intelligibility.

Dysacusis describes an impaired sound quality despite being able to hear, such as distortion or blurring of the speech signal. Those affected hear sounds but cannot distinguish them clearly. This is usually caused by cochlear non-linearities or central processing deficits. Therapy includes targeted hearing training and adaptation of the signal processing in the hearing aid.

Tubal dysfunction occurs when the Eustachian tube does not open and close properly, leading to pressure build-up and effusion in the middle ear. Symptoms include a feeling of pressure, hearing loss and recurring infections. Diagnosis is by tympanometry and tube function test. Treatment ranges from nasal drops and balloon dilatation to tympanostomy tube implantation.