Experimental study of breakout noise characteristics of flexible rectangular duct

Breakout noise is prominent at low frequencies in a rectangular shaped duct due to strong structural-acoustic coupling and is characterized in terms of transverse transmission loss (TTL). The main objective of the present investigation is, to implement intensity based experimental techniques for measuring breakout noise and validate “equivalent unfolded plate” analytical model available in the literature. An experimental test setup is developed to measure input and radiated sound power along with vibration displacement and particle velocity. Using the obtained input and radiated sound power, transverse transmission loss (TTL) and radiation efficiency are calculated. Input sound power is calculated by using an autospectrum of a progressive pressure wave. Radiated sound power is measured using two different methods, namely- intensity probe method (P-P method) and Microflown technique (P-U method). In this present study, numerical model is also developed to predict transverse transmission loss (TTL), radiation efficiency and these results have been corroborated with experimental and analytical results.