Poor utilization of earplugs among military personnel may be due to discomfort caused by the occlusion effect (OE). The OE occurs when an earplug occludes the ear canal, thereby changing bone conduction (BC) hearing and amplifying physiological noises from the wearer. There is a need to understand and reduce the OE in the human ear. A 3D finite element model of the human ear including a 3-chambered spiral cochlea was employed to simulate the OE caused by foam and aerogel earplugs. 90 dB sound pressure was applied at the ear canal entrance and BC sound was applied as vibration of the canal bony wall. The model reported the ear canal pressure and the displacements of the stapes footplate and cochlear basilar membrane with and without earplugs. Without BC stimulation, the foam earplug showed a greater pressure attenuation than the aerogel earplug. However, the foam earplug results were more affected by BC stimulation, with a maximum sound pressure increase of 34 dB, compared to the 21.0 dB increase with the aerogel earplug. The aerogel earplug\'s lower OE demonstrates its promise as an earplug material. Future work with this model will examine BC sound transmission in the cochlea.

If there is sound in the ear canal, you can measure it with a probe microphone in the ear. The following are a few examples of how you might use your real-ear probe microphone measures beyond verifying hearing aid fittings, signal processing, and function of features. A process to simulate hearing loss to educate and support family members and patients is described.

We measure bone-conduction (BC) induced skull velocity, sound pressure at the tympanic membrane (TM) and inner-ear compound-action potentials (CAP) before and after manipulating the ear canal, ossicles, and the jaw to investigate the generation of BC induced ear-canal sound pressures and their contribution to inner-ear BC response in the ears of chinchillas. These measurements suggest that in chinchilla: i.) Vibrations of the bony ear canal walls contribute significantly to BC-induced ear canal sound pressures, as occluding the ear canal at the bone-cartilaginous border causes a 10 dB increase in sound pressure at the TM (PTM) at frequencies below 2 kHz. ii.) The contributions to PTM of ossicular and TM motions when driven in reverse by BC-induced inner-ear sound pressures are small. iii.) The contribution of relative motions of the jaw and ear canal to PTM is small. iv.) Comparison of the effect of canal occlusion on PTM and CAP thresholds point out that BC-induced ear canal sound pressures contribute significantly to bone-conduction stimulation of the inner ear when the ear canal is occluded.

Soft tissue conduction is an additional mode of auditory stimulation which can be initiated either by applying an external vibrator to skin sites not overlying skull bone such as the neck (so it is not bone conduction) or by intrinsic body vibrations resulting, for example, from the heartbeat and vocalization. The soft tissue vibrations thereby induced are conducted by the soft tissues to all parts of the body, including the walls of the external auditory canal. In order for soft tissue conduction to elicit hearing, the soft tissue vibrations which are induced must penetrate into the cochlea in order to excite the inner ear hair cells and auditory nerve fibers. This final stage can be achieved either by an osseous bone conduction mechanism, or, more likely, by the occlusion effect: the vibrations of the walls of the occluded canal induce air pressures in the canal which drive the tympanic membrane and middle ear ossicles and activate the inner ear, acting by means of a more air conduction-like mechanism. In fact, when the clinician applies his stethoscope to the body surface of his patient in order to detect heart sounds or pulmonary air flow, he is detecting soft tissue vibrations.

To facilitate more reliable recordings of the ocular vestibular evoked myogenic potentials (oVEMP) induced by bone-conducted sound using the B81 bone conduction transducer, we preliminarily studied the effects of external auditory meatus occlusion using an earplug on such oVEMP. Eight healthy volunteers (four males and four females, 26-48 years of age, mean age: 34. 5 years) and 14 patients with vestibular disease (2 males and 12 females, 18-59 years of age, mean age: 41.5 years) were enrolled. oVEMP testing was performed using a B81 placed on the temple. Tone bursts (500 Hz, rise/fall time: 2 ms, plateau time: 2 ms, and 70 dB nHL) were presented at a rate of 5.1 Hz. N1-P1 amplitudes were measured and analyzed. Occlusion resulted in significantly larger N1-P1 amplitudes [mean ± SE (SD): 12.3 ± 1.67 (6.71) μV vs. 9.55 ± 1.55 (6.21) μV; p = 0.020, paired t-test]. While four patients did not exhibit any response on either side in the absence of occlusion, all of them showed unilateral or bilateral responses when occlusion was employed. In any patient occlusion did not result in loss of oVEMP responses. External auditory meatus occlusion using an earplug could allow more reliable recordings of bone conduction transducer-induced oVEMP.

To gain insight into the broader implications of the occlusion effect (OE-difference between unoccluded and occluded external canal thresholds), the OE in response to pure tones at 0.5, 1.0, 2.0 and 4.0 kHz to two bone conduction sites (mastoid and forehead) and two soft tissue conduction (STC) sites (under the chin and at the neck) were assessed. The OE was present at the soft tissue sites and at the bone conduction sites, with no statistical difference between them. The OE was significantly greater at lower frequencies, and negligible at higher frequencies. It seems that the vibrations induced in the soft tissues (STC) during stimulation at the soft tissue sites are conducted not only to the inner ear and elicit hearing, but also reach the walls of the external canal and initiate air pressures in the occluded canal which drive the tympanic membrane and excite the inner ear, leading to hearing. Use of a stethoscope by the internist to hear intrinsic body sounds (heartbeat, blood flow) serves as a clear demonstration of STC and its relation to hearing.

To evaluate the effects of conductive hearing loss and occlusion on bone-conducted cervical vestibular evoked myogenic potentials (cVEMPs).
Prospective cohort study conducted in the year 2018. The right ear of each volunteer was evaluated under 3 conditions by using bone-conducted cVEMPs: normal (open external auditory canal), occluded (conductive hearing loss with occlusion effect), and closed (conductive hearing loss without the occlusion effect).
Single academic center.
The study comprised 30 healthy volunteers aged 20 to 35 years (16 women, 14 men). All had normal hearing and no vestibular or auditory pathologies. The thresholds and amplitudes of cVEMP responses were recorded for the 3 conditions. The results of each condition for a particular participant were compared.
As compared with the open condition, the conductive condition increased thresholds by 2.8 dB (P = .01), and the occluded condition decreased thresholds by 3.8 dB (P = .008). The amplitude in the occluded condition was larger than the normal condition and the conductive condition (mean difference: 20.64 [P = .009] and 31.76 [P < .001], respectively).
The occlusion effect is present in cVEMP responses. The mechanism is not due to the conductive hearing loss induced. Clinical implications include potentially altering vestibular function with sealed hearing aids and in the surgically modified ears (ie, obliterated ears and open cavity mastoidectomy).

BACKGROUND: The Lombard effect (LE) is a phenomenon in which speakers adjust their vocal production by raising the volume in noisy environments. As a result, the LE can create problems of vocal strain, fatigue and potential injury.
OBJECTIVE: This study aims to examine the difference in vocal intensity output in subjects wearing unilateral hearing protection versus no hearing protection in the presence of background noise.
METHODS: Each subject was seated inside a sound booth wearing a head-mounted microphone. Subjects were asked to read an excerpt from \"The Rainbow Passage\" while various levels of background noise were played: 50, 60, 70, and 80 dBA (Multitalker Babble). Each noise level was played while the subject was with and without unilateral ear protection (Optime 98 Earmuff [3M]) in random order. The earmuff has a noise reduction rating of 25 dB. After each reading of the text, subjects were asked to rate communication disturbance, vocal clarity, and discomfort during talking using a 10 cm visual analogue scale.
RESULTS: The LE is reduced from 0.38 dB/dB to 0.29 dB/dB with unilateral ear occlusion. However, self-perception of disturbance, clarity and comfort were not affected by unilateral occlusion, only by noise level.
CONCLUSIONS: Unilateral hearing protection reduces the LE and may protect against phonotrauma when speaking in an environment with loud background noise.

Using unmanned robotic systems in military operations such as reconnaissance or surveillance, as well as in many civil applications, is common practice. In this article, the problem of monitoring the specified area of interest by a fleet of unmanned aerial systems is examined. The monitoring is planned via the Cooperative Aerial Model, which deploys a number of waypoints in the area; these waypoints are visited successively by unmanned systems. The original model proposed in the past assumed that the area to be explored is perfectly flat. A new formulation of this model is introduced in this article so that the model can be used in a complex environment with uneven terrain and/or with many obstacles, which may occlude some parts of the area of interest. The optimization algorithm based on the simulated annealing principles is proposed for positioning of waypoints to cover as large an area as possible. A set of scenarios has been designed to verify and evaluate the proposed approach. The key experiments are aimed at finding the minimum number of waypoints needed to explore at least the minimum requested portion of the area. Furthermore, the results are compared to the algorithm based on the lawnmower pattern.

This article examines and evaluates methods, from an audiologist\'s perspective, of reducing common complaints with conventional hearing aids and issues such as the occlusion effect, acoustic feedback, discomfort, and insufficient gain. Although often successful, reducing one problem may have the tradeoff of causing another issue. This article is meant to provide information to the reader regarding modern conventional hearing aids, the means to alleviate common problems in the clinic, and when middle ear implants and osseointegrated implants can be beneficial.