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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
The outer ear consists of the pinna and the ear canal, the inner boundary of which is the eardrum. The pinna (external auricle) of the human serves little useful purpose—apart from being somewhere to hang the spectacles and miscellaneous decorative devices. In some animals the shape is such that it funnels sound into the ear; in some, such as the elephant, a very large pinna provides a high surface area to serve as a heat exchanger. The ear canal (auditory canal, external canal) is roughly the shape of a tube, approximately 30 mm in length and 6 mm in diameter. The air in a tube will resonate at particular frequencies determined by the length of the tube and by the boundary conditions at the ends of the tube (see figure 3.13). The ear canal is closed at one end, by the eardrum, and open at the other.
Occupational Hearing Loss
Published in Ronald Scott, of Industrial Hygiene, 2018
Appearance of readings indicating loss of acuity on an audiogram does not establish industrial noise as the cause. Many programs add readings at 250 and 8000 Hz. Readings at 8000 Hz are important diagnostically. Observed deafness may be due to some cause other than industrial noise exposure if, rather than a notch at 4000 Hz and some recovery by 8000 Hz, the curve is flat or there is an increasing loss of acuity through higher frequencies (Figure 12.4C). A list of disease- or damage-related causes for hearing loss includes: Obstruction of the ear canal. This could be due to accumulated ear wax or a foreign object in the canal.Infection. Infection can cause swelling and obstruction of the ear canal. Infections of the middle ear, often secondary to infections elsewhere, cause temporary or permanent hearing impairment.Allergy. Allergic response to some agents may result in ringing in the ears. Continued exposure may lead to permanent damage.Trauma. An extreme sound such as an explosion can do physical damage to the eardrum or the middle ear.Brain damage. Anything that damages the auditory portion of the brain causes deafness. This could include stroke, hemorrhage, or meningitis.
Analyzing It
Published in Russ Hepworth-Sawyer, Craig Golding, What is Music Production?, 2012
Russ Hepworth-Sawyer, Craig Golding
At the end of the ear canal is the tympanic membrane (more commonly known as the ear drum) sealing off the outside world to our sensitive middle and inner ears. The membrane is flexible and has the important function of acting as though it were the diaphragm on the most precious microphone of all. This receives the sound waves brought down the ear canal and, just like a microphone, converts the movement of the compressions and rarefactions into mechanical movements handled in the middle ear.
Effect of ossicular chain deformity on reverse stimulation considering the overflow characteristics of third windows
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Houguang Liu, Lin Xue, Jianhua Yang, Gang Cheng, Lei Zhou, Xinsheng Huang
To simulate the structural abnormalities of the ossicular chain, we used our previously reported FE model including the ear canal and middle ear (Zhou et al. 2016). In brief, the geometric model of the ear canal and middle ear are based on a series of histological section images collected from a human temporal bone (male, 60 years old, right ear). The volume of the air in the ear canal is 952.18 mm3, and the average length is about 26.32 mm. The volume of the malleus, incus, and stapes are 13.53, 15.54, and 2.95 mm3, respectively. The corresponding mass can be calculated from the measured dimensions. The definition of fluid-structure interaction surface, boundary conditions, and material properties of components in the model are consistent with those reported by Zhou et al. (2016). Figure 2 indicates the FE model of the ear canal and the middle ear. Coupled structural–acoustic analysis of the FE model was conducted using Abaqus (Dassault Systèmes, Johnston, RI, USA).
Anthropometric analysis of 3D ear scans of Koreans and Caucasians for ear product design
Published in Ergonomics, 2018
Wonsup Lee, Xiaopeng Yang, Hayoung Jung, Ilgeun Bok, Chulwoo Kim, Ochae Kwon, Heecheon You
Understanding of the complex shape of the ear is needed for ergonomic design of wearable ear products. Most wearable ear products such as earphones, earmuffs, earplugs, and hearing aid devices interface with the outer ear, which comprises the pinna (auricle) and the ear canal (external acoustic meatus running from pinna to the middle ear). As shown in Figure 1, the concha located in the inner part of the pinna is separated into cymba concha and cavum concha by crus of the helix (Alvord and Farmer 1997), and the ear canal is curved with two bending points (Azernikov 2010; Pirzanski 2010; Sickel et al. 2011). The anatomical and anthropometric characteristics of the ear would be effectively utilised in designing ergonomic shapes of various ear products for fit and comfort (Jung and Jung 2003; Liu 2008).
Quantitative comparison of tympanic membrane displacements using two optical methods to recover the optical phase
Published in Journal of Modern Optics, 2018
Cynthia V. Santiago-Lona, María del Socorro Hernández-Montes, Fernando Mendoza-Santoyo, Jesús Esquivel-Tejeda
The shape, planar dimensions and thickness of the TM vary among various vertebrate species (45, 46). In this work, TMs from two adult healthy cats were used. After euthanizing the cat, the head is immediately removed. The ear canal is stripped off to expose the eardrum, and the temporal bone is kept in place. The membrane remains attached to the tympanic bulla and to the ossicular chain. The TMs had an area of approximately 7 × 5 mm that varies according to the animal’s physiology. The TMs present at least two important challenges that need to be taken into consideration for the study at hand: their low reflectivity and dehydration. To deal with the latter for in ex vivo tests, the sample is maintained in a saline solution and placed in a freezer to preserve it fresh for longer times, and before the experiment begins, the tissue is taken out of the freezer and allowed to defrost at room temperature in the saline solution, and later cleaned. Since TMs are semitransparent in nature, in order to increase the backscattered light, and therefore increase their reflectivity, a white developer coating is applied with great care to avoid damaging the TM. This coating is made with matt acrylic paint diluted in saline solution in the ratio of 1:4. It is worth pointing out that there are no affectations on the physical characteristics of TM or indeed changes to the sound stimuli response that influences the vibration modes due to the developer coat (5).