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Chapter 3 Physics of the Senses
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
A measure of speech comprehension is the most desirable feature of a hearing test. Tests are used in which speech is presented to the subject at a range of intensities and their ability to understand is recorded. Speech audiometry is a valuable test of hearing, although the results depend not only on the hearing ability of the subject but also upon their ability to comprehend the language which is used. Sounds other than speech are also used: a tuning fork can be used by a trained person to assess hearing quite accurately. Sources of sound such as rattles are often used to test a child’s hearing: the sound level required to distract the child can be used as evidence of their having heard a sound. Two commonly used hearing tests are pure-tone audiometry and middle-ear impedance audiometry (tympanometry). Both of these tests use clinical electronic instruments, and they are discussed in detail in Chapter 15. Pure-tone audiometry relies on the co-operation of the subject to report on the audibility of sound over a range of frequencies and intensities to establish hearing threshold. Middle-ear impedance audiometry produces an objective measurement of the function of the middle ear.
Disorders of Hearing
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
Linda M. Luxon, Ronald Hinchcliffe
Pure-tone audiometry is the standard auditory test to document the threshold of hearing (British Society of Audiology, 1981). The technique, performed in a sound-proofed room according to standardized protocols, allows the severity, symmetry and configuration of any hearing loss to be defined across frequencies between 125 and 8,000 Hz in each ear. Electrically generated pure-tones are delivered by headphones, and the subject is required to respond to the quietest tone. Sound may be delivered by air conduction or by bone conduction via a bone vibrator on the mastoid process. In this latter condition, because the intra-aural attenuation for a bone-conducted sound is negligible, the ear which is not being tested must be masked with narrow-band noise centred on the test frequency. Bone-conduction thresholds, which are significantly better than air-conduction thresholds, indicate a disorder affecting the transmission of sound waves through the middle ear into the inner ear – that is, conductive hearing loss – whereas similar bone-conduction and air-conduction thresholds imply a sensorineural hearing loss (Figure 19.5). The determination of normal auditory thresholds was considered to be sufficiently important to aircrew to merit investigation. The results (Wheeler and Dickson, 1952) formed the basis for a standard (1954: British Standard 2497), and this evolved to the current International Organization Standards concerned with the effect of noise on auditory thresholds. These are dealt with in detail in Part 2 of this chapter.
DSP in Hearing Aids
Published in Francis F. Li, Trevor J. Cox, Digital Signal Processing in Audio and Acoustical Engineering, 2019
In audiology, audiometry is used to assess human hearing acuity and diagnose hearing losses. The audiometry procedure is typically undertaken using an audiometer. The result of the examination is plotted in a graph called an audiogram. The audiogram has a logarithmic frequency scale as its horizontal axis and a linear (in dB) vertical axis. Figure 10.2 shows an audiogram sheet. The vertical axis reading is dB hearing level (dBHL). A basic audiogram starts at a low frequency of 125 Hz and increases at octave intervals to a high frequency of 8 kHz. The dBHL is defined for audiometry with pure tone, and should be differentiated from other dB scales used in electronics and acoustics.
Obstructive sleep apnea risk and hearing impairment among occupational noise-exposed male workers
Published in Archives of Environmental & Occupational Health, 2023
Seunghyeon Cho, Won-Ju Park, Ji-Sung Ahn, Dae-Young Lim, Su-Hwan Kim, Jai-Dong Moon
All subjects underwent pure-tone audiometry while avoiding noise exposure for >14 hours. The avoidance of noise exposure was reconfirmed based on the work schedule provided by the company. Hearing thresholds at 1, 2, 3 and 4 kHz for each ear were determined. Pure-tone audiometry was performed by qualified audiometrists using a Madsen Itera II (Otometrics, Denmark) audiometer with TDH-39P headphones. An audiometric device was calibrated annually according to the KOSHA guidelines for audiometry.23 And it passed quality control of audiometric devices conducted by KOSHA every two years.