Decodable but not structured: linear probing enables Underwater Acoustic Target Recognition with pretrained audio embeddings

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Main Authors: Hummel, Hilde I., Bhulai, Sandjai, van der Mei, Rob D., Ghani, Burooj
Format: Preprint
Published: 2026
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_version_ 1866915725949534208
author Hummel, Hilde I.
Bhulai, Sandjai
van der Mei, Rob D.
Ghani, Burooj
author_facet Hummel, Hilde I.
Bhulai, Sandjai
van der Mei, Rob D.
Ghani, Burooj
contents Increasing levels of anthropogenic noise from ships contribute significantly to underwater sound pollution, posing risks to marine ecosystems. This makes monitoring crucial to understand and quantify the impact of the ship radiated noise. Passive Acoustic Monitoring (PAM) systems are widely deployed for this purpose, generating years of underwater recordings across diverse soundscapes. Manual analysis of such large-scale data is impractical, motivating the need for automated approaches based on machine learning. Recent advances in automatic Underwater Acoustic Target Recognition (UATR) have largely relied on supervised learning, which is constrained by the scarcity of labeled data. Transfer Learning (TL) offers a promising alternative to mitigate this limitation. In this work, we conduct the first empirical comparative study of transfer learning for UATR, evaluating multiple pretrained audio models originating from diverse audio domains. The pretrained model weights are frozen, and the resulting embeddings are analyzed through classification, clustering, and similarity-based evaluations. The analysis shows that the geometrical structure of the embedding space is largely dominated by recording-specific characteristics. However, a simple linear probe can effectively suppress this recording-specific information and isolate ship-type features from these embeddings. As a result, linear probing enables effective automatic UATR using pretrained audio models at low computational cost, significantly reducing the need for a large amounts of high-quality labeled ship recordings.
format Preprint
id arxiv_https___arxiv_org_abs_2601_08358
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Decodable but not structured: linear probing enables Underwater Acoustic Target Recognition with pretrained audio embeddings
Hummel, Hilde I.
Bhulai, Sandjai
van der Mei, Rob D.
Ghani, Burooj
Machine Learning
Sound
Audio and Speech Processing
Increasing levels of anthropogenic noise from ships contribute significantly to underwater sound pollution, posing risks to marine ecosystems. This makes monitoring crucial to understand and quantify the impact of the ship radiated noise. Passive Acoustic Monitoring (PAM) systems are widely deployed for this purpose, generating years of underwater recordings across diverse soundscapes. Manual analysis of such large-scale data is impractical, motivating the need for automated approaches based on machine learning. Recent advances in automatic Underwater Acoustic Target Recognition (UATR) have largely relied on supervised learning, which is constrained by the scarcity of labeled data. Transfer Learning (TL) offers a promising alternative to mitigate this limitation. In this work, we conduct the first empirical comparative study of transfer learning for UATR, evaluating multiple pretrained audio models originating from diverse audio domains. The pretrained model weights are frozen, and the resulting embeddings are analyzed through classification, clustering, and similarity-based evaluations. The analysis shows that the geometrical structure of the embedding space is largely dominated by recording-specific characteristics. However, a simple linear probe can effectively suppress this recording-specific information and isolate ship-type features from these embeddings. As a result, linear probing enables effective automatic UATR using pretrained audio models at low computational cost, significantly reducing the need for a large amounts of high-quality labeled ship recordings.
title Decodable but not structured: linear probing enables Underwater Acoustic Target Recognition with pretrained audio embeddings
topic Machine Learning
Sound
Audio and Speech Processing
url https://arxiv.org/abs/2601.08358