The membrane sound absorber (MSA) with a compact magnet has exhibited excellent tunable properties for low-frequency sound absorption. To further clarify its acoustic properties, this paper presents a theoretical model based on a multi-mechanism coupling impedance method. The model predicts the absorption coefficients and resonant frequencies of the MSA at different tuning magnetic states for three cavity configurations. These parameters are then experimentally measured using an impedance tube for model validation, demonstrating good agreement between the measured and predicted values. Subsequent analysis reveals the iron-platelet–magnet resonance mechanism introduced by the tuned magnetic field is the main factor behind the appearance and shift of absorption peaks in the low-frequency region, which are mostly independent of the back cavity. In other words, the MSA with a back cavity of any size can achieve sound absorption in the low-frequency region. This demonstrates the potential of the structure in achieving an ultra-thin, low-frequency, tunable sound-absorber design that can be adapted to different noise sources.

中文翻译：

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带紧凑磁铁的薄膜吸声器的理论模型

具有紧凑磁体的膜吸声器 (MSA) 具有出色的低频吸声可调特性。为了进一步阐明其声学特性，本文提出了一种基于多机制耦合阻抗方法的理论模型。该模型预测了 MSA 在三个腔体配置的不同调谐磁状态下的吸收系数和谐振频率。然后使用阻抗管对这些参数进行实验测量以进行模型验证，证明测量值和预测值之间具有良好的一致性。随后的分析表明，调谐磁场引入的铁-片-磁共振机制是低频区域吸收峰出现和移动的主要因素，这些吸收峰大多与背腔无关。也就是说，具有任意尺寸背腔的MSA都可以实现低频区域的吸声。这证明了该结构在实现可适应不同噪声源的超薄、低频、可调谐吸声器设计方面的潜力。