Use Of Blankets Research Articles

Scarring due to enuresis blankets.

SUMMARY. . Three bed-wetting patients are described in whom the use of enuresis blankets with electric buzzer alarms led to skin ulceration and scarring. In each case the cause was faulty design of the apparatus, resulting in failure of the alarm to ring despite flow of current due to bed-wetting. In two the buzzer alarm could be switched off although the circuit remained live. In the third a run-down battery failed to activate the alarm. Certain design modifications are suggested which would greatly reduce the risk of electrical injury with this apparatus.

The Forty-Fifth Thomas Hawksley Lecture: The Transmission and Radiation of Acoustic Waves by Structures

Of major interest to architects, designers of vehicles, and acousticians is the control of structure-borne sound. Walls and panels are set into vibration by airborne waves or by vibrating mechanisms. The panel so excited will radiate sound and it may carry the vibrations to other panels or bodies.In this lecture, the author will treat the problem of acoustic transmission through walls and panels in the audible frequency range. At low frequencies the panel vibrates as a plate or a stretched membrane. At higher frequencies the panel may behave as a quasiinfinite sheet. Above a particular ‘critical’ frequency, the wavelength of the bending waves in the panel will be longer than the compressional waves in air at the same frequency. The two wavelengths may be brought into coincidence provided the airborne wave impinges on the panel at an angle θ determined bycos θ = ca/ cbwhere caand cbare the speeds of sound in the air and panel, respectively. At the coincidence angle, an airborne wave striking one side of a panel will set it into a level of vibration such that the magnitude of the airborne wave radiated from the other side may be only a few decibels below that of the incident wave. This effect will be discussed both for airborne waves impinging at individual angles of incidence and for waves at many angles of incidence simultaneously.Measurements on plates, concrete sheets, and masonry walls will be presented and analysed. Analysis of the different types of response to airborne wave excitation will be made. Rules for the selection of simple and complex structures for buildings and vehicles will be suggested.Means for reducing the response of structures to airborne wave and mechanical excitation include the use of damping materials in or on the structure, the introduction of discontinuities and the use of sound-absorbing blankets in the structure. Recent data on damping materials and means for utilizing them to produce maximum reduction of flexural waves will be presented. It will be shown that by proper utilization of such materials a structure-borne wave may be attenuated in a given distance by a factor of 10 or more than when utilized in a conventional manner.