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What do hearing tests measure?

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Introduction

WHAT DO HEARING TESTS MEASURE? Intensity and Frequency Hearing tests measure loudness in decibels (intensity) and pitch in Hertz (frequency). The lowest number of decibels (dB) you can hear at different frequencies (Hz) is measured and plotted on a graph called an audiogram. Frequency: Frequency is the number of vibrations per second, expressed as Hertz (Hz). The sounds of speech are in the range of 250 Hz to 4000 Hz. These are commonly tested in a hearing test. Intensity: Sound waves made by something vibrating gently have little intensity (the sound is soft). If an object vibrates strongly, sound waves have greater intensity (the sound is loud). * When sound waves are made by something vibrating slowly, a foghorn or a drum, a low frequency sound occurs. * When sound waves are made by something vibrating quickly, a whistle or a small bell, a high frequency sound occurs. TYPES OF STANDARD HEARING TESTS Pure tone audiometry You listen to a range of beeps and whistles, called pure tones, and indicate when you can hear them. The loudness of each tone is reduced until you can just hear the tone. The softest sounds you can hear are your hearing thresholds marked on an audiogram. ...read more.

Middle

Others find it impossible. Types of hearing loss Conductive hearing loss This type of hearing loss is indicated on the audiogram by normal hearing thresholds obtained via bone conduction and a hearing loss obtained via air conduction (air/bone gap is present). This means that the cochlea is normal and healthy however the hearing loss is caused by blockage or damage in the outer and/or middle ear. Middle-ear infection is a common cause of a conductive hearing loss in young children. It leads to a reduction in the loudness of sounds. It may be possible to treated this type of hearing loss medically or surgically. Sensorineural hearing loss This type of hearing loss is indicated on the audiogram by the hearing thresholds obtained via air conduction and bone conduction being the same yet below normal levels (no air/bone gap). Results from damage or malfunction of the cochlea or the auditory nerve. It can be present at or soon after birth (congenital) or acquired later in life. Exposure to excessive noise and aging process can cause a sensorineural hearing loss. It leads to a loss of loudness as well as a lack of clarity. The quantity and the quality of sound are affected and, sometimes may limit the benefit of a hearing aid. ...read more.

Conclusion

. Oto-acoustic Emission Testing - OAE: It is possible to get an idea about how hair cells in the cochlea are working. A probe that produces a sound is inserted into the ear and measures the very soft sound (oto-acoustic emission) produced by the hair cells as a result. If the OAE is present it indicates normal cochlea function. Brainstem Evoked Response Audiometry - BSERA: This technique provides information on electrical activity generated in response to sound along the nerve pathway, also called brainstem, to the brain. It takes approximately one hour and is usually carried out while the baby is in natural sleep. If this is not possible occasionally it is performed while the person is under GA. Tympanometry and Acoustic Reflex: Tympanometry gives information about the middle ear. * Normal - Compliance: 30 to 150, Middle ear Pressure: -150 to 50 * Middle ear dysfunction - no peak compliance recorded (flat trace) * Eustachian tube dysfunction - Compliance: 30 to 150, Middle ear Pressure: < -150 or > 50 * Perforation/grommet: either no seal obtained or large cavity volume When a person has a normal tympanogram it may be possible to test for the presence of a muscle reflex - acoustic reflex - in the middle ear. ...read more.

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