Momentum and angular momentum reciprocity theorems for acoustic fields.

As a universal theorem applicable to linear physical systems, reciprocity theorems describe the reciprocity between the input and output of linear systems. As for the electromagnetic field, there have been detailed studies on the reciprocity theorems of energy, momentum, and angular momentum, which reveal the correlation between two electromagnetic field sources from different aspects. Based on the fundamentals of linear acoustic theory, the momentum-based and angular momentum-based reciprocity theorems for acoustic fields are derived. They indicate the correlation between two acoustic systems from the perspective of momentum and angular momentum, respectively. On this basis, a systematic summary and analogical study is also performed on various reciprocity theorems for acoustic and electromagnetic fields, which deepens our understanding of the reciprocity theorem as a universal law for linear physical fields. The results obtained in this work can further improve the reciprocity theory of linear acoustic systems, as well as provide theoretical guidance for practical applications, such as audio signal processing and acoustic measurement.