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Publications


2026
Automatic Contextual Audio Denoising
Reference:

D. Luong, K. Drossos, M. Heikkinen, and T. Virtanen, "Automatic Contextual Audio Denoising," in Proceedings of 34th European Signal Conference (EUSIPCO), Bruges, Belgium, 2026

Abstract:

Audio context determines which sound components and sources are relevant and which can be perceived as irrelevant (noise) by listeners. For example, traffic noise is informative in urban surveillance but noise for a phone call at the same location. Most current audio denoising systems apply fixed target-noise definitions, often removing useful components in one context while failing to suppress irrelevant components. To address this, we introduce the concept automatic contextual audio denoising (ACAD) which defines target and noise based on the inferred context. In this work, we restrict context to be associated with an acoustic scene class. We label sound events outside the event distribution of a scene class (noise) as out-of-context (OC) and events typical for that scene as in-context (IC). We implement a deep learning method that automatically infers the context of the audio signal and removes OC components, and benchmark it against variants: without context inference, with oracle context, and with separately provided uninformative context. On paired clean/noisy data across diverse contexts, where OC components in one context may be IC in another, our proposed method outperforms other approaches across standard objective metrics, indicating that the model can infer context and context-dependent processing can enhance denoising.

AI-Generated Summary:

This paper introduces automatic contextual audio denoising (ACAD), where what counts as “noise” depends on the situation rather than being fixed in advance. For example, traffic sounds may be unwanted during a phone call but useful in an urban monitoring application. The proposed system first infers the acoustic context of the recording, such as whether it comes from a street, restaurant, kitchen, or subway, and then uses that context to decide which sounds are relevant and which are out of context and should be removed. To study this problem, the paper also constructs a dataset in which the same type of sound can be considered noise in one context but useful in another, forcing the model to make genuinely context-dependent decisions. The method combines a context-recognition network with a neural denoiser whose processing is guided by the learned context. Experiments show that using inferred context improves denoising compared with a conventional context-independent system, and the best version improves SI-SDR by almost 2 dB over the standard baseline. Interestingly, the learned context performs even better than simply providing the correct scene label, suggesting that the model captures richer information about the acoustic situation than a predefined class alone. The results support the broader idea that future audio-processing systems can benefit from understanding where and under what circumstances a sound occurs before deciding what should be preserved or removed.

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Beyond Omnidirectional: Neural Ambisonics Encoding for Arbitrary Microphone Directivity Patterns using Cross-Attention
Reference:

M. Heikkinen, A. Politis, K. Drossos, and T. Virtanen, "Beyond Omnidirectional: Neural Ambisonics Encoding for Arbitrary Microphone Directivity Patterns using Cross-Attention," in Proceedings of IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Barcelona, Spain, 2026

Abstract:

We present a deep neural network approach for encoding microphone array signals into Ambisonics that generalizes to arbitrary microphone array configurations with fixed microphone count but varying locations and frequency-dependent directional characteristics. Unlike previous methods that rely only on array geometry as metadata, our approach uses directional array transfer functions, enabling accurate characterization of real-world arrays. The proposed architecture employs separate encoders for audio and directional responses, combining them through cross-attention mechanisms to generate array-independent spatial audio representations. We evaluate the method on simulated data in two settings: a mobile phone with complex body scattering, and a free-field condition, both with varying numbers of sound sources in reverberant environments. Evaluations demonstrate that our approach outperforms both conventional digital signal processing-based methods and existing deep neural network solutions. Furthermore, using array transfer functions instead of geometry as metadata input improves accuracy on realistic arrays.

AI-Generated Summary:

This paper tackles a practical problem in spatial audio: how to convert recordings from the small, irregular microphone arrays found in real devices into Ambisonics, a device-independent format used for immersive and 3D audio. Existing neural methods can work well for a specific microphone layout, but often need to be retrained when the array changes, and methods that only use microphone positions cannot describe more realistic effects such as microphone directionality or sound scattering caused by the device body. The proposed method addresses this by giving the neural network not only the recorded audio but also a detailed description of how the microphone array responds to sound coming from different directions and frequencies. Separate neural encoders process the audio and these directional characteristics, and cross-attention combines the two to create an array-independent spatial representation from which the Ambisonics signal is generated. The method is evaluated on simulated microphone arrays in both free-field conditions and a more realistic mobile-phone scenario with complex body scattering. It achieves the best overall signal reconstruction quality in both settings, outperforming conventional Ambisonics encoding and, in realistic phone-like conditions, existing neural approaches. Importantly, the model can generalize to previously unseen microphone configurations without retraining and does so with fewer than one million parameters, showing that detailed knowledge of a device’s directional acoustic behaviour can enable compact and flexible neural spatial-audio capture systems.

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Discriminating Real And Synthetic Super-Resolved Audio Samples Using Embedding-Based Classifiers
Reference:

M. Silaev, K. Drossos, and T. Virtanen, "Discriminating Real And Synthetic Super-Resolved Audio Samples Using Embedding-Based Classifiers," in Proceedings of IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Barcelona, Spain, 2026

Abstract:

Generative adversarial networks (GANs) and diffusion models have recently achieved state-of-the-art performance in audio super-resolution (ADSR), producing perceptually convincing wideband audio from narrowband inputs. However, existing evaluations primarily rely on signal-level or perceptual metrics, leaving open the question of how closely the distributions of synthetic super-resolved and real wideband audio match. Here we address this problem by analyzing the separability of real and super-resolved audio in various embedding spaces. We consider both middle-band (4→16~kHz) and full-band (16→48~kHz) upsampling tasks for speech and music, training linear classifiers to distinguish real from synthetic samples based on multiple types of audio embeddings. Comparisons with objective metrics and subjective listening tests reveal that embedding-based classifiers achieve near-perfect separation, even when the generated audio attains high perceptual quality and state-of-the-art metric scores. This behavior is consistent across datasets and models, including recent diffusion-based approaches, highlighting a persistent gap between perceptual quality and true distributional fidelity in ADSR models.

AI-Generated Summary:

This paper asks a simple but important question about audio super-resolution: when a generative model creates the missing high-frequency content of a low-bandwidth recording, does the result merely sound realistic, or is it actually statistically similar to real wideband audio? To investigate this, the study evaluates several neural super-resolution systems for speech and music, including GAN-based and diffusion-based models, and compares real and generated audio not only with conventional signal-quality metrics and listening tests, but also by testing whether simple classifiers can tell them apart from learned audio representations. The results reveal a striking mismatch: some generated samples achieve very high perceptual quality and can sound close to the original wideband recordings, yet classifiers operating on audio embeddings can still distinguish real from synthetic samples with near-perfect accuracy. This behaviour is observed across different datasets, sampling-rate expansion tasks, and modern generative models. The findings therefore show that good perceptual quality and strong objective scores do not necessarily mean that a generative model has learned the true distribution of real audio, highlighting an important limitation in how audio super-resolution systems are currently evaluated and suggesting that representation-based tests can expose differences that conventional metrics and listening tests may miss.

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Dynamic Clustering for Cross-Segment Permutation Alignment in Long Speech Separation
Reference:

Y. Wang, A. Politis, K. Drossos,  and T. Virtanen, "Dynamic Clustering for Cross-Segment Permutation Alignment in Long Speech Separation," in Proceedings of the  IEEE International Workshop on Machine Learning for Signal Processing (MLSP), Atlanta, U.S.A., 2026

Abstract:

Long speech separation typically employs a segment-separation-stitch paradigm where recordings are divided into short segments, processed independently, and stitched together. Its challenge lies in predicting cross-segment permutations. This paper proposes a training-free dynamic clustering approach for cross-segment permutation alignment using speaker embedding reference pools. The method predicts the permutation using the cosine similarity between current segment embeddings and the reference pools. The approach updates reference pools by retaining the most representative speaker embeddings based on their overall cosine similarity with existing references. As a plug-and-play post-processing module compatible with existing separation models, the proposed method demonstrates superior performance compared to existing methods on dense and sparse long speech scenarios, particularly in challenging sparse scenarios with extended utterance gaps, and further shows robustness to speaker count estimation errors in unknown speaker count scenarios.

AI-Generated Summary:

This paper addresses a practical problem in long speech separation: when a long recording is split into shorter segments and each segment is separated independently, the same speaker may appear in different output channels from one segment to the next. This makes it difficult to reconstruct continuous, speaker-consistent audio, especially in meetings, interviews, or other recordings where speakers may remain silent for long periods. The proposed method solves this by maintaining a small, continuously updated reference pool of speaker embeddings for each output stream. For every new segment, the system compares its speaker embeddings with these reference pools and assigns the segment to the most likely speakers, while retaining only the most representative and reliable embeddings over time. The approach requires no additional training and can be added as a post-processing stage to existing speech-separation systems. Experiments on long recordings with both dense and sparse speech show that the method substantially improves cross-segment speaker consistency, reaching 98.5% permutation accuracy in dense scenarios and 96.8% in sparse ones, with separation quality close to the oracle upper bound. It is particularly effective when there are long gaps between utterances, where conventional overlap- or clustering-based methods degrade, and it remains robust even when the number of speakers is estimated incorrectly.

Neural Array-Generic Direction-of-Arrival Estimation Exploiting Array Transfer Functions
Reference:

M. Heikkinen, A. Politis, K. Drossos,  and T. Virtanen, "Neural Array-Generic Direction-of-Arrival Estimation Exploiting Array Transfer Functions," in Proceedings of the 19th International Workshop on Acoustic Signal Enhancement (IWAENC), Milan, Italy, 2026

Abstract:

Direction-of-arrival (DoA) estimation is a key component of multichannel audio processing, yet many deep learning approaches remain tied to the microphone arrays used during training and generalize poorly to unseen devices. This paper proposes an array-generic neural DoA estimation framework using measured or simulated complex directional array transfer functions (ATFs) matched to real-world multi-microphone devices. The method processes multichannel spectrograms and ATF metadata with separate convolutional encoders, fuses the resulting representations through cross-attention, and predicts source directions using a multi-source Cartesian vector output formulation. Experiments on simulated 2D and 3D localization tasks under reverberation and diffuse babble noise show that the proposed approach generalizes to previously unseen arrays, including mobile-phone-like configurations, without major performance degradation, while remaining competitive with conventional and learning-based baselines.

AI-Generated Summary:

This paper addresses a major limitation of neural sound-source localization: most deep-learning methods work well only with the microphone array they were trained on, making deployment to new devices difficult without retraining. The proposed method instead uses detailed acoustic information about the microphone array—its array transfer functions, which describe how sounds arriving from different directions are captured by the microphones—rather than relying only on microphone positions. A neural network separately processes the recorded audio and these array characteristics, then combines them through cross-attention to estimate the directions of one or more sound sources. This allows the same model to operate on previously unseen microphone layouts, including realistic mobile-phone-like arrays where the device body alters the incoming sound field. Experiments in reverberant and noisy environments show that the method generalizes to new arrays with only moderate loss in performance and remains effective as the number of simultaneous sources increases. Classical MUSIC localization is still more accurate for simple single-source cases, but its performance degrades much faster as scenes become more complex, whereas the proposed neural approach remains more stable and can jointly detect and localize multiple sources. The results demonstrate that conditioning neural localization systems on the actual acoustic behaviour of a device is a promising route toward microphone-array-independent spatial audio processing.

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