Abstract: The present invention relates to a device for accomplishing noise reduction in a photoacoustic gas detector using a sound damping element and/or a background or reference microphone where a preferably larger external volume that acts as a sound damping element (SDE) is coupled to a smaller volume through which the gas diffuses. The coupling is accomplished in such a way that the externally generated sound waves incident upon the photoacoustic detector are adequately attenuated by the larger volume SDE without adversely affecting diffusion of the gaseous species of interest through the smaller volume for measurement by the detector. Preferably this is accomplished by coupling the larger SDE volume to the smaller gas diffusion volume by a long and thin pressure channel.

Abstract: The present invention relates to a device for accomplishing noise reduction in a photoacoustic gas detector using a sound damping element and/or a background or reference microphone where a preferably larger external volume that acts as a sound damping element (SDE) is coupled to a smaller volume through which the gas diffuses. The coupling is accomplished in such a way that the externally generated sound waves incident upon the photoacoustic detector are adequately attenuated by the larger volume SDE without adversely affecting diffusion of the gaseous species of interest through the smaller volume for measurement by the detector. Preferably this is accomplished by coupling the larger SDE volume to the smaller gas diffusion volume by a long and thin pressure channel.

Abstract: A joint between two textile materials in web form, one of them preferably being a plurality of parallel yarns forming a monolayer or multilayer sheet, and the other one a fabric. The joint is an adhesive or heat sealed bonding member which is equipped at least on one of its surfaces with a heat shield. The joint is flexible, thin, tear and heat resistant, not attacked by chemical reagents, solvents or vapors. It can be formed in a novel apparatus for heat sealing by means of heat sealable strips which are reinforced by heat resistant materials and which are heat sealed together across the yarn sheet.