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Audiometry: The testing of the acuity of the sense of hearing to determine the thresholds of the lowest intensity levels at which an individual can hear a set of tones. The frequencies between 125 and 8000 Hz are used to test air conduction thresholds and the frequencies between 250 and 4000 Hz are used to test bone conduction thresholds.Audiometry, Pure-Tone: Measurement of hearing based on the use of pure tones of various frequencies and intensities as auditory stimuli.Audiometry, Evoked Response: A form of electrophysiologic audiometry in which an analog computer is included in the circuit to average out ongoing or spontaneous brain wave activity. A characteristic pattern of response to a sound stimulus may then become evident. Evoked response audiometry is known also as electric response audiometry.Auditory Threshold: The audibility limit of discriminating sound intensity and pitch.Hearing Loss, High-Frequency: Hearing loss in frequencies above 1000 hertz.Hearing Disorders: Conditions that impair the transmission of auditory impulses and information from the level of the ear to the temporal cortices, including the sensorineural pathways.Acoustic Impedance Tests: Objective tests of middle ear function based on the difficulty (impedance) or ease (admittance) of sound flow through the middle ear. These include static impedance and dynamic impedance (i.e., tympanometry and impedance tests in conjunction with intra-aural muscle reflex elicitation). This term is used also for various components of impedance and admittance (e.g., compliance, conductance, reactance, resistance, susceptance).Hearing Loss, Noise-Induced: Hearing loss due to exposure to explosive loud noise or chronic exposure to sound level greater than 85 dB. The hearing loss is often in the frequency range 4000-6000 hertz.Hearing Loss: A general term for the complete or partial loss of the ability to hear from one or both ears.Hearing Tests: Part of an ear examination that measures the ability of sound to reach the brain.Noise, Occupational: Noise present in occupational, industrial, and factory situations.Hearing: The ability or act of sensing and transducing ACOUSTIC STIMULATION to the CENTRAL NERVOUS SYSTEM. It is also called audition.Tinnitus: A nonspecific symptom of hearing disorder characterized by the sensation of buzzing, ringing, clicking, pulsations, and other noises in the ear. Objective tinnitus refers to noises generated from within the ear or adjacent structures that can be heard by other individuals. The term subjective tinnitus is used when the sound is audible only to the affected individual. Tinnitus may occur as a manifestation of COCHLEAR DISEASES; VESTIBULOCOCHLEAR NERVE DISEASES; INTRACRANIAL HYPERTENSION; CRANIOCEREBRAL TRAUMA; and other conditions.Acoustic Stimulation: Use of sound to elicit a response in the nervous system.Otoacoustic Emissions, Spontaneous: Self-generated faint acoustic signals from the inner ear (COCHLEA) without external stimulation. These faint signals can be recorded in the EAR CANAL and are indications of active OUTER AUDITORY HAIR CELLS. Spontaneous otoacoustic emissions are found in all classes of land vertebrates.Hearing Loss, Sensorineural: Hearing loss resulting from damage to the COCHLEA and the sensorineural elements which lie internally beyond the oval and round windows. These elements include the AUDITORY NERVE and its connections in the BRAINSTEM.Ear Protective Devices: Personal devices for protection of the ears from loud or high intensity noise, water, or cold. These include earmuffs and earplugs.Evoked Potentials, Auditory, Brain Stem: Electrical waves in the CEREBRAL CORTEX generated by BRAIN STEM structures in response to auditory click stimuli. These are found to be abnormal in many patients with CEREBELLOPONTINE ANGLE lesions, MULTIPLE SCLEROSIS, or other DEMYELINATING DISEASES.Auditory Fatigue: Loss of sensitivity to sounds as a result of auditory stimulation, manifesting as a temporary shift in auditory threshold. The temporary threshold shift, TTS, is expressed in decibels.Pitch Discrimination: The ability to differentiate tones.Hearing Loss, Conductive: Hearing loss due to interference with the mechanical reception or amplification of sound to the COCHLEA. The interference is in the outer or middle ear involving the EAR CANAL; TYMPANIC MEMBRANE; or EAR OSSICLES.Audiometry, Speech: Measurement of the ability to hear speech under various conditions of intensity and noise interference using sound-field as well as earphones and bone oscillators.Noise: Any sound which is unwanted or interferes with HEARING other sounds.Pitch Perception: A dimension of auditory sensation varying with cycles per second of the sound stimulus.Bone Conduction: Transmission of sound waves through vibration of bones in the SKULL to the inner ear (COCHLEA). By using bone conduction stimulation and by bypassing any OUTER EAR or MIDDLE EAR abnormalities, hearing thresholds of the cochlea can be determined. Bone conduction hearing differs from normal hearing which is based on air conduction stimulation via the EAR CANAL and the TYMPANIC MEMBRANE.Evoked Potentials, Auditory: The electric response evoked in the CEREBRAL CORTEX by ACOUSTIC STIMULATION or stimulation of the AUDITORY PATHWAYS.Auditory Perception: The process whereby auditory stimuli are selected, organized, and interpreted by the organism.Auditory Cortex: The region of the cerebral cortex that receives the auditory radiation from the MEDIAL GENICULATE BODY.Psychoacoustics: The science pertaining to the interrelationship of psychologic phenomena and the individual's response to the physical properties of sound.Otoscopy: Examination of the EAR CANAL and eardrum with an OTOSCOPE.Auditory Diseases, Central: Disorders of hearing or auditory perception due to pathological processes of the AUDITORY PATHWAYS in the CENTRAL NERVOUS SYSTEM. These include CENTRAL HEARING LOSS and AUDITORY PERCEPTUAL DISORDERS.Sound: A type of non-ionizing radiation in which energy is transmitted through solid, liquid, or gas as compression waves. Sound (acoustic or sonic) radiation with frequencies above the audible range is classified as ultrasonic. Sound radiation below the audible range is classified as infrasonic.Reflex, Acoustic: Intra-aural contraction of tensor tympani and stapedius in response to sound.Tympanoplasty: Surgical reconstruction of the hearing mechanism of the middle ear, with restoration of the drum membrane to protect the round window from sound pressure, and establishment of ossicular continuity between the tympanic membrane and the oval window. (Dorland, 28th ed.)Auditory Pathways: NEURAL PATHWAYS and connections within the CENTRAL NERVOUS SYSTEM, beginning at the hair cells of the ORGAN OF CORTI, continuing along the eighth cranial nerve, and terminating at the AUDITORY CORTEX.Neural Analyzers: A term used in Eastern European research literature for the functional neural unit that provides the basis for differential sensitivity; the analyzer consists of receptor, afferent nerves, and their central connections. (From Campbell's Psychiatric Dictionary, 8th ed.)Music: Sound that expresses emotion through rhythm, melody, and harmony.Hearing Aids: Wearable sound-amplifying devices that are intended to compensate for impaired hearing. These generic devices include air-conduction hearing aids and bone-conduction hearing aids. (UMDNS, 1999)Auditory Perceptual Disorders: Acquired or developmental cognitive disorders of AUDITORY PERCEPTION characterized by a reduced ability to perceive information contained in auditory stimuli despite intact auditory pathways. Affected individuals have difficulty with speech perception, sound localization, and comprehending the meaning of inflections of speech.Ear Diseases: Pathological processes of the ear, the hearing, and the equilibrium system of the body.Vestibular Diseases: Pathological processes of the VESTIBULAR LABYRINTH which contains part of the balancing apparatus. Patients with vestibular diseases show instability and are at risk of frequent falls.Vertigo: An illusion of movement, either of the external world revolving around the individual or of the individual revolving in space. Vertigo may be associated with disorders of the inner ear (EAR, INNER); VESTIBULAR NERVE; BRAINSTEM; or CEREBRAL CORTEX. Lesions in the TEMPORAL LOBE and PARIETAL LOBE may be associated with FOCAL SEIZURES that may feature vertigo as an ictal manifestation. (From Adams et al., Principles of Neurology, 6th ed, pp300-1)Otosclerosis: Formation of spongy bone in the labyrinth capsule which can progress toward the STAPES (stapedial fixation) or anteriorly toward the COCHLEA leading to conductive, sensorineural, or mixed HEARING LOSS. Several genes are associated with familial otosclerosis with varied clinical signs.Cochlear Nerve: The cochlear part of the 8th cranial nerve (VESTIBULOCOCHLEAR NERVE). The cochlear nerve fibers originate from neurons of the SPIRAL GANGLION and project peripherally to cochlear hair cells and centrally to the cochlear nuclei (COCHLEAR NUCLEUS) of the BRAIN STEM. They mediate the sense of hearing.Stapes Surgery: Surgery performed in which part of the STAPES, a bone in the middle ear, is removed and a prosthesis is placed to help transmit sound between the middle ear and inner ear.Loudness Perception: The perceived attribute of a sound which corresponds to the physical attribute of intensity.Hearing Loss, Functional: Hearing loss without a physical basis. Often observed in patients with psychological or behavioral disorders.Speech Perception: The process whereby an utterance is decoded into a representation in terms of linguistic units (sequences of phonetic segments which combine to form lexical and grammatical morphemes).Hearing Loss, Bilateral: Partial hearing loss in both ears.Vestibular Function Tests: A number of tests used to determine if the brain or balance portion of the inner ear are causing dizziness.Sound Spectrography: The graphic registration of the frequency and intensity of sounds, such as speech, infant crying, and animal vocalizations.Muscle Tonus: The state of activity or tension of a muscle beyond that related to its physical properties, that is, its active resistance to stretch. In skeletal muscle, tonus is dependent upon efferent innervation. (Stedman, 25th ed)Tectum Mesencephali: The dorsal portion or roof of the midbrain which is composed of two pairs of bumps, the INFERIOR COLLICULI and the SUPERIOR COLLICULI. These four colliculi are also called the quadrigeminal bodies (TECTUM MESENCEPHALI). They are centers for visual sensorimotor integration.Cochlea: The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH.Electronystagmography: Recording of nystagmus based on changes in the electrical field surrounding the eye produced by the difference in potential between the cornea and the retina.Ear, Middle: The space and structures directly internal to the TYMPANIC MEMBRANE and external to the inner ear (LABYRINTH). Its major components include the AUDITORY OSSICLES and the EUSTACHIAN TUBE that connects the cavity of middle ear (tympanic cavity) to the upper part of the throat.Voice: The sounds produced by humans by the passage of air through the LARYNX and over the VOCAL CORDS, and then modified by the resonance organs, the NASOPHARYNX, and the MOUTH.Olivary Nucleus: A part of the MEDULLA OBLONGATA situated in the olivary body. It is involved with motor control and is a major source of sensory input to the CEREBELLUM.Ear: The hearing and equilibrium system of the body. It consists of three parts: the EXTERNAL EAR, the MIDDLE EAR, and the INNER EAR. Sound waves are transmitted through this organ where vibration is transduced to nerve signals that pass through the ACOUSTIC NERVE to the CENTRAL NERVOUS SYSTEM. The inner ear also contains the vestibular organ that maintains equilibrium by transducing signals to the VESTIBULAR NERVE.Textile Industry: The aggregate business enterprise of manufacturing textiles. (From Random House Unabridged Dictionary, 2d ed)Inferior Colliculi: The posterior pair of the quadrigeminal bodies which contain centers for auditory function.Perceptual Masking: The interference of one perceptual stimulus with another causing a decrease or lessening in perceptual effectiveness.Basilar Membrane: A basement membrane in the cochlea that supports the hair cells of the ORGAN OF CORTI, consisting keratin-like fibrils. It stretches from the SPIRAL LAMINA to the basilar crest. The movement of fluid in the cochlea, induced by sound, causes displacement of the basilar membrane and subsequent stimulation of the attached hair cells which transform the mechanical signal into neural activity.Echolocation: An auditory orientation mechanism involving the emission of high frequency sounds which are reflected back to the emitter (animal).Chiroptera: Order of mammals whose members are adapted for flight. It includes bats, flying foxes, and fruit bats.Semicircular Canals: Three long canals (anterior, posterior, and lateral) of the bony labyrinth. They are set at right angles to each other and are situated posterosuperior to the vestibule of the bony labyrinth (VESTIBULAR LABYRINTH). The semicircular canals have five openings into the vestibule with one shared by the anterior and the posterior canals. Within the canals are the SEMICIRCULAR DUCTS.Neuroma, Acoustic: A benign SCHWANNOMA of the eighth cranial nerve (VESTIBULOCOCHLEAR NERVE), mostly arising from the vestibular branch (VESTIBULAR NERVE) during the fifth or sixth decade of life. Clinical manifestations include HEARING LOSS; HEADACHE; VERTIGO; TINNITUS; and FACIAL PAIN. Bilateral acoustic neuromas are associated with NEUROFIBROMATOSIS 2. (From Adams et al., Principles of Neurology, 6th ed, p673)Signal Detection, Psychological: Psychophysical technique that permits the estimation of the bias of the observer as well as detectability of the signal (i.e., stimulus) in any sensory modality. (From APA, Thesaurus of Psychological Index Terms, 8th ed.)Vestibulocochlear Nerve Diseases: Pathological processes of the VESTIBULOCOCHLEAR NERVE, including the branches of COCHLEAR NERVE and VESTIBULAR NERVE. Common examples are VESTIBULAR NEURITIS, cochlear neuritis, and ACOUSTIC NEUROMA. Clinical signs are varying degree of HEARING LOSS; VERTIGO; and TINNITUS.Sound Localization: Ability to determine the specific location of a sound source.Reaction Time: The time from the onset of a stimulus until a response is observed.Occupational Exposure: The exposure to potentially harmful chemical, physical, or biological agents that occurs as a result of one's occupation.Magnetoencephalography: The measurement of magnetic fields over the head generated by electric currents in the brain. As in any electrical conductor, electric fields in the brain are accompanied by orthogonal magnetic fields. The measurement of these fields provides information about the localization of brain activity which is complementary to that provided by ELECTROENCEPHALOGRAPHY. Magnetoencephalography may be used alone or together with electroencephalography, for measurement of spontaneous or evoked activity, and for research or clinical purposes.Presbycusis: Gradual bilateral hearing loss associated with aging that is due to progressive degeneration of cochlear structures and central auditory pathways. Hearing loss usually begins with the high frequencies then progresses to sounds of middle and low frequencies.Cross-Sectional Studies: Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time.Occupational Diseases: Diseases caused by factors involved in one's employment.Cochlear Nucleus: The brain stem nucleus that receives the central input from the cochlear nerve. The cochlear nucleus is located lateral and dorsolateral to the inferior cerebellar peduncles and is functionally divided into dorsal and ventral parts. It is tonotopically organized, performs the first stage of central auditory processing, and projects (directly or indirectly) to higher auditory areas including the superior olivary nuclei, the medial geniculi, the inferior colliculi, and the auditory cortex.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Cochlear Implants: Electronic hearing devices typically used for patients with normal outer and middle ear function, but defective inner ear function. In the COCHLEA, the hair cells (HAIR CELLS, VESTIBULAR) may be absent or damaged but there are residual nerve fibers. The device electrically stimulates the COCHLEAR NERVE to create sound sensation.Vocalization, Animal: Sounds used in animal communication.Time Perception: The ability to estimate periods of time lapsed or duration of time.Hearing Loss, Sudden: Sensorineural hearing loss which develops suddenly over a period of hours or a few days. It varies in severity from mild to total deafness. Sudden deafness can be due to head trauma, vascular diseases, infections, or can appear without obvious cause or warning.Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Tympanic Membrane: An oval semitransparent membrane separating the external EAR CANAL from the tympanic cavity (EAR, MIDDLE). It contains three layers: the skin of the external ear canal; the core of radially and circularly arranged collagen fibers; and the MUCOSA of the middle ear.Gerbillinae: A subfamily of the Muridae consisting of several genera including Gerbillus, Rhombomys, Tatera, Meriones, and Psammomys.Electrodes, Implanted: Surgically placed electric conductors through which ELECTRIC STIMULATION is delivered to or electrical activity is recorded from a specific point inside the body.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.Discrimination (Psychology): Differential response to different stimuli.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Cochlear Implantation: Surgical insertion of an electronic hearing device (COCHLEAR IMPLANTS) with electrodes to the COCHLEAR NERVE in the inner ear to create sound sensation in patients with residual nerve fibers.Vibration: A continuing periodic change in displacement with respect to a fixed reference. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Callithrix: A genus of the subfamily CALLITRICHINAE occurring in forests of Brazil and Bolivia and containing seventeen species.Deafness: A general term for the complete loss of the ability to hear from both ears.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Echo-Planar Imaging: A type of MAGNETIC RESONANCE IMAGING that uses only one nuclear spin excitation per image and therefore can obtain images in a fraction of a second rather than the minutes required in traditional MRI techniques. It is used in a variety of medical and scientific applications.Hair Cells, Auditory: Sensory cells in the organ of Corti, characterized by their apical stereocilia (hair-like projections). The inner and outer hair cells, as defined by their proximity to the core of spongy bone (the modiolus), change morphologically along the COCHLEA. Towards the cochlear apex, the length of hair cell bodies and their apical STEREOCILIA increase, allowing differential responses to various frequencies of sound.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.