Influence of air masses on microphone vibration sensitivity

A study is presented of the primary design parameters that influence the vibration sensitivity of a microphone. The sensitivity to vibration is generally determined by the mass of the pressure-sensing diaphragm along with the mass of air that moves with it. The sound-sensing performance is improved as the pressure-sensing diaphragm is made thinner, but for a thin enough diaphragm, the moving air mass is not negligible relative to that of the diaphragm itself. In the present study, we develop a simple duct-acoustic model to account for the effect of the co-vibrating air. It is shown that an idealized massless, thin microphone diaphragm will still produce unwanted vibration signal due to acceleration of the air masses within the microphone. For a small microphone, the predicted pressure related acceleration sensitivity is found to be a simple function of the mass per unit area of the air inside of the microphone package. The acceleration sensitivity predicted using a finite element model of a one micrometer thick clamped flexible silicon diaphragm agrees with that predicted by the simple duct model. Measured and predicted acceleration sensitivities are compared for several MEMS and sub-miniature electret microphones of different back volume lengths . It is found that the primary design parameter determining vibration sensitivity for these microphones is the effective length of the column of air inside the microphone’s packaging. Microphones that have longer air-filled volumes had greater pressure related acceleration sensitivity.

A case of postapoplectic hemichorea with sensory and autonomic disorders

Th. Dosuzkov and Ed. Bena (Revue v. Neurologii i psychiatrii, 1928, nos. 3 and 4). Choreic contractions were noted in the right half of the face and right limbs. These contractions decreased under the influence of volitional tension, increased with distraction of attention, with emotions and unpleasant peripheral sensations. On the right side, the patient had friendly motions of the imitation type, muscle hypotonia, absence of setting reflexes, the presence of tactile hypeesthesia and decreased vibration sensitivity on the right side, miosis and increased sweating on the right.

Importance of electrostatic massage in the rehabilitation of the patients with vibration disease and with shoulder joint diseases

The results of the use of electrostatic massage in the miners with vibration disease and with shoulder joint diseases are presented. In the all patients the rehabilitation program included electrostatic massage on the ELGOS device using a lead-out electrode according to the local-segmental method. Patients of the comparison group underwent manual massage of similar areas. Before and after the treatment, the clinical manifestations of vibration disease were evaluated by vibration sensitivity test using a Rydel-Seiffer vibrotone C 64 Hz / C 128 Hz. The dynamics of functional activity indices in the patients with shoulder joint diseases was assessed using a visual analog scale questionnaire. The work showed that the electrostatic massage contributes to a faster restoration of vibration sensitivity, the volume of movements in large joints and a reduction in the clinical manifestations of vibration disease (pain in the fingers, paresthesia, numbness, etc.), which has an advantage in the conditions of the COVID-19 pandemic, since the direct impact of the masseur’s hands on the patient’s body is excluded.

Vibrotherapy in medical practice

A review of literature sources on the use of vibrotherapy in physiotherapy is presented. In the mechanism of action of vibrotherapy, the leading role belongs to vibration sensitivity the main link between the human body and the impact on it of the environment. The patient's tissues are affected using devices for vibrotherapy, using mechanical vibrations with a frequency of 10 to 250 Hz in continuous or pulsed modes. Vibrotherapy has trophic, reflex, neuroprotective, myorelaxing, anti-inflammatory, analgesic, oxygenating, antioxidant effects and is recommended for prevention, treatment and rehabilitation in various nosologies and conditions of the human body. In addition to the above, vibrotherapeutic effects contribute to the formation of protective and adaptive mechanisms.

Test of Vibrations Influence on the Measurement Accuracy in the Precise Digital Leveller Trimble Dini 03 and Comparison of Its Vibration Sensitivity with Leveller Ni 002

The article presents findings from research on the effect of vibrations on the accuracy of measurement with an automatic precise digital leveller. A special research station was created to induce vibrations on a leveller and to measure vibration parameters that affect staff reading. It contains description of discovered relationship between the vibration parameters and the mean error of a single height difference measurement. The range of frequencies for which the measurement was possible was estimated. The reliability of the measured values obtained under specific vibration conditions was also analysed. The results of current research were compared with similar studies on analogue leveller Ni 002. The conclusions described in this paper can be helpful in engineering measurements under adverse conditions of ambient vibrations.

USH2A is a skin end-organ protein necessary for vibration sensing in mice and humans

Fingertip mechanoreceptors comprise sensory neuron endings together with specialized skin cells that form the end-organ. Exquisitely sensitive vibration-sensing neurons are associated with Meissner’s corpuscles and Pacinian corpuscles1. Such end-organ structures have been recognized for more than 160 years, but their exact functions have remained a matter of speculation. Here we examined the role of USH2A in touch sensation in humans and mice. The USH2A gene encodes a transmembrane protein with a very large extracellular domain. Pathogenic USH2A mutations cause Usher syndrome associated with hearing loss and visual impairment2. We show that patients with biallelic pathogenic USH2A mutations also have profound impairments in vibrotactile touch perception. Similarly, mice lacking the USH2A protein showed severe deficits in a forepaw vibrotactile discrimination task. Forepaw rapidly-adapting mechanoreceptors (RAMs) recorded from Ush2a−/− mice innervating Meissner’s corpuscles showed profound reductions in their vibration sensitivity. However, the USH2A protein was not expressed in sensory neurons, but was found in specialized terminal Schwann cells in Meissner’s corpuscles. Loss of this large extracellular tether-like protein in corpuscular end-organs innervated by RAMs was sufficient to reduce the vibration sensitivity of mechanoreceptors. Thus, USH2A expressed in corpuscular end-organs associated with vibration sensing is required to properly perceive vibration. We propose that cells within the corpuscle present a tether-like protein that may link to mechanosensitive channels in sensory endings to facilitate small amplitude vibration detection essential for the perception of fine textured surfaces.