V.P.Sahno, V.V.Fedorov
Determination of sound speed in exhaust gases of drive of interior combustion

Acoustic bulletin, Vol. 3 1, (2000) p.73-77
There is considered a method of determination of a sound speed in the exhaust gas of the drive of interior combustion. Such determination is a necessary requirement at designing of jet silencers. The embodying of a method is carried out by measuring of the attenuation of acoustic waves. The noise level of an exhaust without a silencer and with it is measured. Using the obtained data the efficiency of noise attenuation is determined. From formula on calculation of the noise attenuation efficiency of a jet silencer the formula for calculation of a speed of sound in an exhaust is derived. In this formula all the parameters are known: level of the efficiency of a silencer, frequency of an exhaust, ratio of areas of the cross sections of a silencer and supply pipe, length of a silencer. The sound speed determined in this way can be utilized in further not only for drives of that type, for which measuring and calculations were made, but also (with some approximation) for some other types of drives. The design of an experimental installation which allows to implement a sectional method, is proposed and theoretically justified. The error of method and ways to rise its precision are discussed.
sound speed, the exhaust gases, reactive silencer, noise level