针对稀有生物声学片段,提出高效主动学习选段方法
Greedy Volume Maximization of Gradient Embeddings for Long-Tailed Frame-Level Bioacoustic Active Learning
- 基于梯度嵌入体积最大化,贪心选择最具信息量的音频片段
- 在10次实验中显著优于其他方法,尤其提升罕见物种叫声识别率
- 适合标注成本高、类别极不均衡的生态监测场景
生物声学呼叫类型分类依赖昂贵的人工标注。主动学习通过挑选少量片段供专家标注,降低负担。但目标叫声极为稀疏,类别分布长尾严重,必须精准投入有限预算于少数稀有且高信息量片段。本文提出BADGE-Greedy-DPP,一种确定性批量选择器,贪心地添加其BADGE梯度嵌入使批次张成体积最大化的片段;由于该对数体积目标为子模函数,贪心策略保证批次价值至少达到最优值的(1-1/e)倍,这一理论保障是现有k-means++和MCMC DPP采样启发式所不具备的。任务还存在时间粒度不匹配问题:评分函数作用于整段,但信息帧极少,均匀平均会淹没关键信号。我们证明,当在帧级应用BADGE时,预测残差会加权聚合伪梯度,因此预测置信度高的无呼叫帧贡献小,而单个不确定的稀有呼叫帧仍能主导片段方向。在稀疏、不平衡的斑鬣狗叫声数据集上进行10次运行,BADGE-Greedy-DPP在整体性能和罕见呼叫类型表现上均优于所有对比查询策略,包括最强非BADGE基线MFFT及两种原始BADGE遍历方式。
原文摘要 · Abstract (English)
Bioacoustic call-type classification relies on costly expert annotation. Active learning can reduce this burden by selecting a small batch of segments for expert annotation and using the labeled segments for training the classifier. The setting is hard: the target calls are extremely sparse and the call-type distribution is long-tailed, so a tight budget must be spent on the few rare, informative segments. We propose BADGE-Greedy-DPP, a deterministic batch selector that greedily adds the segment whose BADGE gradient embedding most enlarges the volume spanned by the batch; because this log-volume objective is submodular, the greedy rule guarantees a batch value at least a (1-1/e) fraction of the optimum of this objective, a guarantee not provided by BADGE's existing k-means++ and MCMC DPP sampling heuristics. There is also a temporal granularity mismatch in the task. The acquisition function scores whole segments, yet the informative frames inside them are few. Uniform averaging therefore washes them out. We show that the BADGE construction naturally addresses this mismatch when applied frame-wise, as prediction residuals weight the aggregated pseudo-gradient, so confidently predicted no-call frames contribute little while a single uncertain rare-call frame can still set the segment's direction. Across 10 runs on a sparse, imbalanced hyena call-type dataset, BADGE-Greedy-DPP achieves the best overall and rare-call-type performance among all compared query strategies, including MFFT, the strongest non-BADGE baseline, and the two vanilla BADGE traversals.
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