Active Control of Environmental Noise, V: The Effect of Environmental Change on the Stability of Free Field Sound Cancelling Systems

Active Control of Environmental Noise, Vi: Performance of a Fundamental Free-Field Sound Cancelling System

“…As increases, the stability bands progressively shrink and "nally disappear (have zero bandwidth) according to the properties as discussed in section 2. Figure 6(a) may appear irrational; however, the logic is more apparent in the bigger picture revealed for example in reference [5]. Although the stability bands are unique, i.e., they have di!erent eigenvalues, fortunately they tend in general to have similar properties.…”

“…The e!ect of three-dimensional primary sources, out-of-phase primary sources, re#ecting surfaces and steady wind on the shadow generation has been considered in reference [4]. The e!ect of environmental change on the stability of adaptive process was considered in reference [5].…”

Large-scale outdoor sound field control

“…Betlehem et al (2018) show that indoors, the late part of control filters is especially sensitive to temperature changes. Active control of sound outdoors has mainly been studied numerically (Berkhoff, 2005;Nakashima and Hodgson, 2005;Stein et al, 2019;Wright and Atmoko, 2001) or at single points only (Lapini et al, 2018).…”

Active Control of Environmental Noise, Vii: Performance of Multi-Frequency, Multi-Channel, Freefield Sound Cancelling Systems

“…In reference [3], it is shown as to how the cancellation system is a!ected with the detailed e!ects of complex three-dimensional primary sources, ground re#ection and steady cross winds. In reference [6], the e!ect of transient environmental changes such as re#ections from moving surfaces and varying wind on the stability of the adaptive process is considered. More complex propagating medium e!ects such as turbulence, varying temperature gradients, absorption and non-linear e!ects on the cancellation performance are not considered.…”