Many speech enhancement algorithms suffer from musical noise - an estimation residue noise consisting of music-like varying tones. To reduce this annoying noise, some speech enhancement algorithms require post-processing. However, a lack of auditory perception theories about musical noise limits the effectiveness of musical noise reduction methods. Scientists now have some understanding of the human auditory system, thanks to the advances in hearing research across multiple disciplines - anatomy, physiology, psychology, and neurophysiology. Auditory models, such as the gammatone filter bank and the Meddis inner hair cell model, have been developed to simulate the acoustic to neuron transduction process. The auditory models generate the neuron firing signals called the cochleagram. Cochleagram analysis is a powerful tool to investigate musical noise. We use auditory perception theories in our musical noise investigations. Some auditory perception theories (e.g., volley theory and auditory scene analysis theories) suggest that speech perception is an auditory grouping process. Temporal properties of neuron firing signals, such as period and rhythm, play important roles in the grouping process. The grouping process generates a foreground speech stream, a background noise stream, and possibly additional streams. We assume that musical noise is the result of grouping to the background stream the neuron firing signals whose temporal properties are different from the ones grouped to the foreground stream. Based on this hypothesis, we believe that a musical noise reduction method should increase the probability of grouping the enhanced neuron firing signals to the foreground speech stream, or decrease the probability of grouping them into the background stream. We propose a post-processing musical noise reduction method for the auditory Wiener filter speech enhancement method, in which we employ a proposed complex gammatone filter bank for the cochlear decomposition. The results of a subjective listening test of our speech enhancement system show that the proposed musical noise reduction method is effective. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-05-28 16:11:28.374

Angesichts ihrer unüberschaubaren Ausdifferenzierung scheint es heute kaum noch möglich, eine allgemeingültige Definition von Musik zu finden. Ausgehend von diesem Problem nimmt dieser Text ihre Randbereiche in den Fokus: Die Grenzen des Hörens, wie sie in extremen Formen experimenteller Musik, etwa im Harsh Noise Wall, ausgelotet werden und die Grenzen des Vernehmens, wie sie sich im stets metaphorischen Sprechen über Musik abzeichnen. Als unüberschreitbare Grenze dieser beiden Randzonen bildet die Klangfarbe das Zentrum der Argumentation und den Abschluss der Überlegungen. / Today it seems nearly impossible to find a universally valid definition of music due to its vast differentiation. Ensuing from this problem, this text focuses on music’s borders: the hearing limits as they are explored in extreme forms of experimental music (like Harsh Noise Wall) and the margins of understanding as they are shown in the use of metaphors in speaking about music. Timbre is discussed as an uncrossable border of these two aspects. These thoughts form both the focus and the conclusion of this text.

This diploma thesis focuses on issues connected with music pollution, which has an impact on us whenever we are near noisy, disturbing and irritating music that we have to listen to involuntarily. We are exposed to this kind of noise on daily basis and we usually ignore the consequences it may bring. This thesis consists of two parts. The theoretical part describes the main characteristics, with made research and the most common forms of musical noise - musical coulisse, background music. The main source of information was my questionnaire filled in by 136 respondents. It presents a complex overview on this poorly analyzed and complicated issue as well as shows in which public places we are exposed to the music pollution frequently and how we perceive it. As the main result of my study I consider the finding that majority of people find a musical noise in public places disturbing. The most irritating places seem to be restaurants and waiting rooms. However some silent music is rather required in places like restaurants, coffee shops and waiting rooms. Younger generation prefers loud music in shops, in contrary to middle age respondents that would prefer silent music. People are usually not protecting themselves much against a musical noise. And if yes, they try to sort it out by negotiations - in...

We often have to face the fact that several signals are mixed together in unknown environment. The signals must be first extracted from the mixture in order to interpret them correctly. This problem is in signal processing society called blind source separation. This dissertation thesis deals with multi-channel separation of audio signals in real environment, when the source signals outnumber the sensors. An introduction to blind source separation is presented in the first part of the thesis. The present state of separation methods is then analyzed. Based on this knowledge, the separation systems implementing fuzzy time-frequency mask are introduced. However these methods are still introducing nonlinear changes in the signal spectra, which can yield in musical noise. In order to reduce musical noise, novel methods combining time-frequency binary masking and beamforming are introduced. The new separation system performs linear spatial filtering even if the source signals outnumber the sensors. Finally, the separation systems are evaluated by objective and subjective tests in the last part of the thesis.