Abstract: The invention relates to a method and a device for comparing acoustic input signals fed into an input device (1) with acoustic reference signals stored in a memory (3). The first step in this case is to carry out a harmonic analysis of the input signals in a frequency analyzer (4) connected to the input device (1) and the memory (3), in order to produce a time-dependent Fourier spectrum. Thereafter, preselectable characteristics of the Fourier spectrum are determined as input signal coordinates for defining an n-dimensional input signal vector, where n is a number of the characteristics. Thereafter, the input signal vector is checked for correspondence of respectively corresponding coordinates within prescribed tolerances with at least one reference signal vector, which is defined in the same way and thereafter stored in the memory (3).

Abstract: A chimney comprises an external shaft and an inner lining sub-divided into several portions arranged one above the other, each portion having an inner and an outer shell with an annular space containing compressed air therein at a higher pressure than the flue gas, each portion of the inner lining being carried by a support construction so as to be spaced from the external shaft.