Recent interest has arisen in the realisation of nonreciprocal acoustic devices that achieve unid... more Recent interest has arisen in the realisation of nonreciprocal acoustic devices that achieve unidirectional sound transmission. In other words, these devices allow perfect transmission from waves travelling in one direction, whilst blocking waves travelling in the opposite direction. These devices have thus been described as the acoustic analogue of an electrical diode and could be useful in many applications. There are a variety of passive and active devices that have been designed based on the con-cept of acoustic metamaterials to achieve unidirectional transmission by introducing non-linearities or breaking spatial and temporal symmetries. This paper will investigate how unidirectional transmission can be achieved using active control within a one-dimensional duct. The proposed active control system has the capability to manipulate either the positive or negative travelling waves within the duct in order to achieve zero transmission in one direction, whilst allowing perfect trans...
Nonreciprocal acoustic devices typically break reciprocity by introducing nonlinearities or direc... more Nonreciprocal acoustic devices typically break reciprocity by introducing nonlinearities or directional biasing. However, these devices are generally not fully adaptable and often use resonant cavities, which only exhibit nonreciprocal behaviour over a narrow bandwidth. Therefore, to overcome these challenges, this paper investigates how wave-based active control can be used to achieve broadband nonreciprocal behaviour in a one-dimensional environment. Wave-based controller architectures are described for both transmission and absorption control and, through simulation and experimental implementations, it is shown that they can achieve broadband nonreciprocal behaviour. Importantly, the direction of nonreciprocal behaviour can be straightforwardly reversed.
The Journal of the Acoustical Society of America, 2018
Acoustic metamaterials are subwavelength-engineered structures that can exhibit behaviour not see... more Acoustic metamaterials are subwavelength-engineered structures that can exhibit behaviour not seen in conventional materials. The effective material properties for acoustic metamaterials are the bulk modulus and density. Negative effective material properties can create band gaps, where wave propagation is forbidden. Hence, acoustic metamaterials can achieve high levels of noise control performance. Active control has been combined with passive acoustic metamaterials to enhance the level of attenuation or broaden the bandwidth of the band gap. However, the width of the band gaps for these materials are still limited by the use of resonators. This study will investigate whether active control can be employed to directly minimise the effective material properties, which requires an optimization procedure. To begin to understand this optimization problem, the effective material properties have been calculated as a function of the real and imaginary parts of the control source strength ...
Recent interest has arisen in the realisation of nonreciprocal acoustic devices that achieve unid... more Recent interest has arisen in the realisation of nonreciprocal acoustic devices that achieve unidirectional sound transmission. In other words, these devices allow perfect transmission from waves travelling in one direction, whilst blocking waves travelling in the opposite direction. These devices have thus been described as the acoustic analogue of an electrical diode and could be useful in many applications. There are a variety of passive and active devices that have been designed based on the con-cept of acoustic metamaterials to achieve unidirectional transmission by introducing non-linearities or breaking spatial and temporal symmetries. This paper will investigate how unidirectional transmission can be achieved using active control within a one-dimensional duct. The proposed active control system has the capability to manipulate either the positive or negative travelling waves within the duct in order to achieve zero transmission in one direction, whilst allowing perfect trans...
Nonreciprocal acoustic devices typically break reciprocity by introducing nonlinearities or direc... more Nonreciprocal acoustic devices typically break reciprocity by introducing nonlinearities or directional biasing. However, these devices are generally not fully adaptable and often use resonant cavities, which only exhibit nonreciprocal behaviour over a narrow bandwidth. Therefore, to overcome these challenges, this paper investigates how wave-based active control can be used to achieve broadband nonreciprocal behaviour in a one-dimensional environment. Wave-based controller architectures are described for both transmission and absorption control and, through simulation and experimental implementations, it is shown that they can achieve broadband nonreciprocal behaviour. Importantly, the direction of nonreciprocal behaviour can be straightforwardly reversed.
The Journal of the Acoustical Society of America, 2018
Acoustic metamaterials are subwavelength-engineered structures that can exhibit behaviour not see... more Acoustic metamaterials are subwavelength-engineered structures that can exhibit behaviour not seen in conventional materials. The effective material properties for acoustic metamaterials are the bulk modulus and density. Negative effective material properties can create band gaps, where wave propagation is forbidden. Hence, acoustic metamaterials can achieve high levels of noise control performance. Active control has been combined with passive acoustic metamaterials to enhance the level of attenuation or broaden the bandwidth of the band gap. However, the width of the band gaps for these materials are still limited by the use of resonators. This study will investigate whether active control can be employed to directly minimise the effective material properties, which requires an optimization procedure. To begin to understand this optimization problem, the effective material properties have been calculated as a function of the real and imaginary parts of the control source strength ...
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Papers by Joe Tan