烟草天蛾幼虫虽然缺乏传统的耳朵构造，却能察觉胡蜂等捕食者的逼近。研究团队为了厘清其听觉机制，在专门隔绝外界噪音与振动的无响室中进行实验。他们首先测出幼虫对平台物理振动的反应阈值，随后改以空气传播的声音作为刺激。结果显示，幼虫在振动强度低于该阈值时仍对声音产生反应，证实牠们能够独立感知空气中的声波，而非仅仅依赖基底振动。

大部分哺乳动物与昆虫通常仰赖鼓膜器官或充气气囊等构造来感应声压，但幼虫身上并无此类器官。研究人员在显微镜下观察并锁定幼虫体表的特殊微细毛发，进而进行拔除毛发的对照实验。实验发现，当特定毛发被移除后，幼虫对不同频率声音的防御反应显著下降，证实这些超灵敏的微小毛发正是充当听觉器官的关键构造，且不同毛发可能对特定频率具有调谐性。

毛发感知声波粒子运动速度的机制，为声学技术带来了全新启发。传统麦克风主要依赖薄膜来侦测声压，而模仿毛发结构的新型感测器则能同时测量空气粒子速度与声波来源方向。这项仿生研究未来有望推动更便宜、具方向定位功能的新一代麦克风问世，并大幅改善助听器等设备辨识声音方位与音量的效能。

Tobacco hornworm caterpillars lack traditional ears yet can detect approaching predators like wasps. To uncover this auditory mechanism, researchers conducted experiments inside an anechoic chamber engineered to block external noise and vibrations. After establishing the threshold for caterpillars' responses to direct physical platform vibrations, they introduced airborne sound stimuli. The caterpillars continued reacting to sounds even when platform vibrations fell below their physical threshold, confirming they perceive airborne sound independently of substrate vibration.

While most mammals and insects rely on tympanal membranes or air sacs to sense sound pressure waves, caterpillars possess no such structures. Researchers examined them under a microscope and hypothesized that tiny body hairs act as auditory sensors. By selectively removing these hairs, they observed a dramatic decline in defensive reactions across specific sound frequencies, indicating that these supersensitive microscopic hairs serve as the caterpillar's ears and are tuned to distinct frequencies.

This discovery of hair-based perception of air particle velocity offers promising engineering applications for modern acoustics. Conventional microphones rely on membranes to measure sound pressure levels, but bio-inspired designs mimicking caterpillar hairs could detect both particle velocity and wave direction. Such advancements could lead to cheaper, highly directional microphones and significantly improve hearing aid technology by providing users with precise auditory orientation.