Acoustic analysis of the effect of personal protective equipment on speech understanding: lessons for clinical environments.

Objective: The use of various types of filtering facepiece class 3 (FFP3) mask have become commonplace since the Covid-19 outbreak. These have been evaluated in terms of efficacy regarding aerosol filtration but less emphasis has been placed on the acoustic effects of such masks and their consequences for clinical communication.

Design: A microphone 65 cm from a sound-producing Head and Torso Simulator (wearing the masks) was used to measure attenuation via a tone sweep.

Full geometry dependence of index contrast in photorefractive polymer composites.

Detailed analysis of the relationship between the experimental geometry and the holographic contrast in photorefractive polymers is important for applications, such as angle multiplexing in holographic data storage. In this paper the field dependent photogeneration efficiency is introduced into the complete reorientational model to provide a full account of the electric field and geometrical dependence of the index contrast. The interaction of a local grating and the photorefractive grating is also considered.