An adaptive quarter-wave tube that uses the sliding-Goertzel algorithm for estimation of phase

Adaptive muffler based on controlled flow valves

“…The quarter wavelength resonator has a limited application as most sources have varying frequency and varying gas temperature, hence varying the speed of sound, and can be adversely affected by grazing flow. 10 Herschel-Quincke tubes are also suitable for tonal noise and its harmonics. 12 The proposed system ( Fig.…”

“…2,6,[10][11][12] The main advantage of this muffler is its ability to control its effects in real time and consequently achieve higher noise reduction under various levels of input noise. Their efficiency in noise reduction can be tuned to desired levels and/or to the welfare of the users' subjective perspective.…”

“…Cherrier et al 13 created perforated panel resonators with an active control of their openings, so called necks. Howard and Craig 10,14 presented an adaptive quarter-wave resonator to attenuate the exhaust noise of a V6 petrol engine, adapting to changes in engine operating conditions (speed and load), and exhaust gas temperature. In available literature on adaptive mufflers, the main acoustic path is manipulated in a way that increases transmission loss at different operating conditions.…”

A Muffler with Adaptive Acoustic Properties

“…In recent years, a great deal of effort has been put into the research of adaptive reactive mufflers [6], [11], [15] and [16]. Instead of loudspeakers, adaptive mufflers use non-acoustic actuators to eliminate the problems of acoustic feedback, which is one of the prevailing problems in the practical usage of ANC.…”

“…Kostek and Franchek [19] proposed a hybrid resonator with an actively controlled cavity of the Helmholtz resonator. Howard and Craig [15] and [20] presented an adaptive quarterwave resonator to attenuate the exhaust noise of a V6 petrol engine, adapting to changes in engine operating conditions (revolutions per minute (RPM) and load), and exhaust gas temperature.…”