International Conference on Information and Communication Security, 2001
Low frequency noise has a masking effect on speech, which significantly reduces the speech intell... more Low frequency noise has a masking effect on speech, which significantly reduces the speech intelligibility. Usually, in order to overcome the masking effect the sound level of the communication signal is increased. Exposure to the communication system then causes hearing damage. A feasible approach is to reduce the low frequency noise by using active techniques combined with a method for reducing the noise in the intercom microphone signal. In order to achieve an efficient low frequency noise attenuation inside the headset an active hybrid headset is proposed, and in order to suppress the background noise in speech signals spectral subtraction is used. Improved low frequency noise attenuation enables lower communication levels and reduces the risk for hearing damage.
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand -outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
IEEE Transactions on Speech and Audio Processing, Jul 1, 1999
This article presents an evaluation of multiple reference adaptive algorithms. Two least mean squ... more This article presents an evaluation of multiple reference adaptive algorithms. Two least mean squares-types (LMS-types) and a Newton-type algorithm are considered. The special structure of the adaptive filtering problem implies that the Newton-type algorithm can be implemented with the same numerical complexity as LMS-type algorithms. The concept of a first filtered-x Newton algorithm is thus introduced
Active noise control has proven to be an efficient solution to low frequency noise problems in ma... more Active noise control has proven to be an efficient solution to low frequency noise problems in many different applications. A large part of these applications are concerned with harmonic noise control and typically require control systems with several inputs and outputs. As the systems grow, the demand for processor capacity increases rapidly, resulting in large and expensive hardware platforms. As multiple-input, multiple-output noise control is restricted to the control of periodic noise, a controller structure that is adapted to the signal type may significantly reduce the requirements on the hardware capacity. This paper discusses a complex, time-domain controller that is designed for the control of harmonic components. The structure of the controller is simple, easily implemented and can easily be extended to handle any number of noise references and any number of harmonics. The convergence properties of a multiple-input, multiple-output control system depends largely on the acoustic coupling between the active sources and the control sensors. To get accurate and stable control it is necessary to use normalization, i.e. a weighting function that optimizes the controller for each control source. With the presented controller structure, the use of normalization is straightforward and a number of different approaches for normalization is discussed as well as examples from practical inplementations.
A common problem in small vessels is the high levels of low frequency sound, usually produced by ... more A common problem in small vessels is the high levels of low frequency sound, usually produced by the engines and/or the propellers. Due to the low frequency character of the noise, the primary concern is usually not the potential risk of hearing damage, but the masking effect that reduces speech intelligibility. Another aspect is loss of sleep due to noise, which increases the potential risk for accidents during work onboard caused by tiredness. For this reason, a multiple reference, multiple input, multiple output active control system was implemented and tested in a small patrol boat. The boat was 13 meters long and powered by two 800 hp MTU Diesel engines. The primary tonal components in the drivers cabin were reduced by 20 dB.
International Journal of Acoustics and Vibration, 2000
ABSTRACT In many applications of noise control, the greatest annoyance is caused by periodic low ... more ABSTRACT In many applications of noise control, the greatest annoyance is caused by periodic low frequency noise. Successful reduction of such noise can often be achieved by using an active noise control system with narrowband feedforward control. If several noise sources contribute to the sound field, a multiple-reference control system is usually required. This type of system allows the reference signals from each noise source to be processed individually within the controller, thereby enabling individual control of the sound field from each noise source. The present paper addresses the problem of controlling noise from two sources that are more or less synchronized. A typical application is the control of propeller-generated noise within a twin propeller aircraft. To find out whether a multiple-reference controller is necessary, or if a single-reference controller is sufficient, the performance of a single- versus twin-reference control algorithm is evaluated in a comparative study. The study is performed as a computer simulation (off-line evaluation) using real-life data recorded in a Dornier 328 under different flight conditions. The results demonstrate that the twin-reference controller performs better than the single-reference whenever there is a slight deviation in the rotational speed of the two propellers. The paper also treats the generation of reference signals. The approach presented is based on a fixed sampling rate and uses a sliding FFT filtering technique.
Vibration induced sound in the car of a light high speed train is of great interest since the lig... more Vibration induced sound in the car of a light high speed train is of great interest since the light structure makes it more resonant. Low weight is important and and the aim is to decrease the weight of future trains significantly, compared to the X2000. Classical sound attenuation techniques are good for higher frequencies but active techniques are more suitable when lowering the low frequency induced noise in the car. This work therefore addresses a problem that is likely to occur in future trains, due to the decreased weight. The sleepers are a dominant excitation source for this case, and this implies a periodic excitation of 85 Hz when the train is running at 200 km/h. The sleeper frequency excitation will be an even larger problem when the car has a lower weight as well. This paper describes an active vibration isolation, or damping, where the goal is to reduce the sound inside the car due to the sleeper frequency excitation not the vibrations levels. Four actuators have been used and both an AVC as well as an ASAC control strategy has been tested and the results are presented. Tests have been performed on a full scale train in a lab as well as on track at approximately 200 km/h.
The book, edited by Catharina Dyrssen, draws on coclusions from two larger artistic research proj... more The book, edited by Catharina Dyrssen, draws on coclusions from two larger artistic research project on urban sound environments, sound art, acoustic space, and spatial aspects of sound. The chapters comprise reflections on sound quality ans sound awareness, sound design and audio editing, technical solutions for artistic problems, and how sound can be composed and used in architectural and urban design. In text and images the four authors discuss a number of investigative projects performed within the artistic and interdisciplinary research group Urban Sound Institute.
Two new controller configurations for broad band adaptive noise control have been examined. In th... more Two new controller configurations for broad band adaptive noise control have been examined. In the proposed structures, a certain amount of the properties of the acoustic system are modelled by a fixed part of the controller which is therefore less flexible than a completely adaptive control system. The benefit with these configurations are that the adaptive part can be small
Proceedings of SPIE, the International Society for Optical Engineering, 1997
The sound levels in the sleeping quarters and the mess-room of fishing boats are sometimes too hi... more The sound levels in the sleeping quarters and the mess-room of fishing boats are sometimes too high. It is especially important to keep the sound levels down since the crew have to spend several days on the boat. This implies a long exposure time to low frequency noise. Even during sleep the crew does not have a hearing rest. It is therefore of interest to decrease sound levels in specific areas to give the crew hearing rest. The advantage with an ANC system is that it can be used as a retrofit kit, and the installation does not force the owner to keep the boat in the harbor for long times, compared to a passive treat of the noise problem. In order to evaluate how much sound level decrease it is possible to achieve, a volumetric ANC system has been tested. The typical fishing boat is equipped with one main engine. The engine is typically mounted using a passive isolation, but this does not decrease the sound levels enough. A brief review and discussion of the background noise situation are made in this paper. Since the boat has one engine, a single reference, multiple input, multiple output active noise control system, SR-MIMO ANC, was used using loudspeakers and microphones and an adaptive system based on a DSP. The SR-MIMO ANC system consists of one reference signal, four loudspeakers and six microphones. The results from a field test are presented in the paper and the results are commented.
This paper treats the practical aspects of the prediction, implementation and verification of an ... more This paper treats the practical aspects of the prediction, implementation and verification of an active noise control system. The system was implemented in a mock-up of a Saab 340 propeller aircraft. A search algorithm, based on simulated annealing using the metropolis sampler was used to determine the positions for the control sources and sensors. The sound field was generated by a specially designed noise simulation system, using 12 individually controlled loudspeakers and a DSP--based signal generator. A version of the individually normalized complex lms algorithm was implemented for the control of the sound field. The prediction and verification of the active control system, was made in 20 evaluation positions, distributed at ear level above the seats. This is the second paper in a series of two, concerning the preparation, selection and verification of an active noise control system. Part I contains a theoretical treatment with some general guidelines for the implementation. Paper II is focused on the practical aspects of the implementation and verification.
This article’s pivotal theme is: “How to compose a site-specific sound-art installation for a com... more This article’s pivotal theme is: “How to compose a site-specific sound-art installation for a commercial space in order to improve conditions, while taking perceptual, social, aesthetical, temporal and spatial criteria into account” The interdisciplinary, art-based research approach is derived from the concept of acousmatics, i.e. the process of apprehending any sound, the source of which is invisible. Acousmatic perception concerns the everyday identification process; when lacking visual contact with the sound source, we automatically seek references, such as social (what produces the sound and what is my relation to it?), aesthetical, spatial and temporal (e.g. orientation and demarcation). The acousmatic concept identifies phenomena based on individually, culturally and spatially conditioned experiences. Today, a shopping culture dominates urban space. Indoor malls expose us to all types of acousmatically perceived sounds: jingles, signals, music and muzak from public loudspeakers, mobile devices, etc. In this respect, one could claim that the soundscape of the shopping culture embodies an acousmatic environment. In 2009, the research and sound-art group Urban Sound Institute (USIT) created a permanent sound installation in a shopping mall (Gallerian) located in downtown Stockholm. This installation serves as a case study for the present paper. The artistic assignment involved the creation of a meeting place without material devices as well as the enhancement of the overall atmosphere. The research objective was to elucidate different qualities of the sound installation in regard to the acousmatics of the shopping mall, promoting discussions on the articulation of sound-space configurations in relation to time and site-specific context, issues on musical-architectural qualities as well as objective, subjective and inter-subjective interrelationships between the experience of the sound-art installation and the experience of the shopping mall soundscape. Other applied, interrelated concepts are metabolic environment and masking- and cutting effects.
Sound and other spaces is a book about urban sound environments, sound art, acoustic space, and s... more Sound and other spaces is a book about urban sound environments, sound art, acoustic space, and spatial aspects of sound. The texts in this book comprise personal reflections on sound quality and sound awareness, sound design and audio editing, technical solutions for artistic problems, and how sound can be composed and used in architectural design and city planning. In texts and images the authors present a number of projects performed within the artistic and interdisciplinary research group Urban Sound Institute (USIT). We hope that readers will find this book handy and easy to use and that it will serve as a bridge between specialists and an interested general public.
International Conference on Information and Communication Security, 2001
Low frequency noise has a masking effect on speech, which significantly reduces the speech intell... more Low frequency noise has a masking effect on speech, which significantly reduces the speech intelligibility. Usually, in order to overcome the masking effect the sound level of the communication signal is increased. Exposure to the communication system then causes hearing damage. A feasible approach is to reduce the low frequency noise by using active techniques combined with a method for reducing the noise in the intercom microphone signal. In order to achieve an efficient low frequency noise attenuation inside the headset an active hybrid headset is proposed, and in order to suppress the background noise in speech signals spectral subtraction is used. Improved low frequency noise attenuation enables lower communication levels and reduces the risk for hearing damage.
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand -outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
IEEE Transactions on Speech and Audio Processing, Jul 1, 1999
This article presents an evaluation of multiple reference adaptive algorithms. Two least mean squ... more This article presents an evaluation of multiple reference adaptive algorithms. Two least mean squares-types (LMS-types) and a Newton-type algorithm are considered. The special structure of the adaptive filtering problem implies that the Newton-type algorithm can be implemented with the same numerical complexity as LMS-type algorithms. The concept of a first filtered-x Newton algorithm is thus introduced
Active noise control has proven to be an efficient solution to low frequency noise problems in ma... more Active noise control has proven to be an efficient solution to low frequency noise problems in many different applications. A large part of these applications are concerned with harmonic noise control and typically require control systems with several inputs and outputs. As the systems grow, the demand for processor capacity increases rapidly, resulting in large and expensive hardware platforms. As multiple-input, multiple-output noise control is restricted to the control of periodic noise, a controller structure that is adapted to the signal type may significantly reduce the requirements on the hardware capacity. This paper discusses a complex, time-domain controller that is designed for the control of harmonic components. The structure of the controller is simple, easily implemented and can easily be extended to handle any number of noise references and any number of harmonics. The convergence properties of a multiple-input, multiple-output control system depends largely on the acoustic coupling between the active sources and the control sensors. To get accurate and stable control it is necessary to use normalization, i.e. a weighting function that optimizes the controller for each control source. With the presented controller structure, the use of normalization is straightforward and a number of different approaches for normalization is discussed as well as examples from practical inplementations.
A common problem in small vessels is the high levels of low frequency sound, usually produced by ... more A common problem in small vessels is the high levels of low frequency sound, usually produced by the engines and/or the propellers. Due to the low frequency character of the noise, the primary concern is usually not the potential risk of hearing damage, but the masking effect that reduces speech intelligibility. Another aspect is loss of sleep due to noise, which increases the potential risk for accidents during work onboard caused by tiredness. For this reason, a multiple reference, multiple input, multiple output active control system was implemented and tested in a small patrol boat. The boat was 13 meters long and powered by two 800 hp MTU Diesel engines. The primary tonal components in the drivers cabin were reduced by 20 dB.
International Journal of Acoustics and Vibration, 2000
ABSTRACT In many applications of noise control, the greatest annoyance is caused by periodic low ... more ABSTRACT In many applications of noise control, the greatest annoyance is caused by periodic low frequency noise. Successful reduction of such noise can often be achieved by using an active noise control system with narrowband feedforward control. If several noise sources contribute to the sound field, a multiple-reference control system is usually required. This type of system allows the reference signals from each noise source to be processed individually within the controller, thereby enabling individual control of the sound field from each noise source. The present paper addresses the problem of controlling noise from two sources that are more or less synchronized. A typical application is the control of propeller-generated noise within a twin propeller aircraft. To find out whether a multiple-reference controller is necessary, or if a single-reference controller is sufficient, the performance of a single- versus twin-reference control algorithm is evaluated in a comparative study. The study is performed as a computer simulation (off-line evaluation) using real-life data recorded in a Dornier 328 under different flight conditions. The results demonstrate that the twin-reference controller performs better than the single-reference whenever there is a slight deviation in the rotational speed of the two propellers. The paper also treats the generation of reference signals. The approach presented is based on a fixed sampling rate and uses a sliding FFT filtering technique.
Vibration induced sound in the car of a light high speed train is of great interest since the lig... more Vibration induced sound in the car of a light high speed train is of great interest since the light structure makes it more resonant. Low weight is important and and the aim is to decrease the weight of future trains significantly, compared to the X2000. Classical sound attenuation techniques are good for higher frequencies but active techniques are more suitable when lowering the low frequency induced noise in the car. This work therefore addresses a problem that is likely to occur in future trains, due to the decreased weight. The sleepers are a dominant excitation source for this case, and this implies a periodic excitation of 85 Hz when the train is running at 200 km/h. The sleeper frequency excitation will be an even larger problem when the car has a lower weight as well. This paper describes an active vibration isolation, or damping, where the goal is to reduce the sound inside the car due to the sleeper frequency excitation not the vibrations levels. Four actuators have been used and both an AVC as well as an ASAC control strategy has been tested and the results are presented. Tests have been performed on a full scale train in a lab as well as on track at approximately 200 km/h.
The book, edited by Catharina Dyrssen, draws on coclusions from two larger artistic research proj... more The book, edited by Catharina Dyrssen, draws on coclusions from two larger artistic research project on urban sound environments, sound art, acoustic space, and spatial aspects of sound. The chapters comprise reflections on sound quality ans sound awareness, sound design and audio editing, technical solutions for artistic problems, and how sound can be composed and used in architectural and urban design. In text and images the four authors discuss a number of investigative projects performed within the artistic and interdisciplinary research group Urban Sound Institute.
Two new controller configurations for broad band adaptive noise control have been examined. In th... more Two new controller configurations for broad band adaptive noise control have been examined. In the proposed structures, a certain amount of the properties of the acoustic system are modelled by a fixed part of the controller which is therefore less flexible than a completely adaptive control system. The benefit with these configurations are that the adaptive part can be small
Proceedings of SPIE, the International Society for Optical Engineering, 1997
The sound levels in the sleeping quarters and the mess-room of fishing boats are sometimes too hi... more The sound levels in the sleeping quarters and the mess-room of fishing boats are sometimes too high. It is especially important to keep the sound levels down since the crew have to spend several days on the boat. This implies a long exposure time to low frequency noise. Even during sleep the crew does not have a hearing rest. It is therefore of interest to decrease sound levels in specific areas to give the crew hearing rest. The advantage with an ANC system is that it can be used as a retrofit kit, and the installation does not force the owner to keep the boat in the harbor for long times, compared to a passive treat of the noise problem. In order to evaluate how much sound level decrease it is possible to achieve, a volumetric ANC system has been tested. The typical fishing boat is equipped with one main engine. The engine is typically mounted using a passive isolation, but this does not decrease the sound levels enough. A brief review and discussion of the background noise situation are made in this paper. Since the boat has one engine, a single reference, multiple input, multiple output active noise control system, SR-MIMO ANC, was used using loudspeakers and microphones and an adaptive system based on a DSP. The SR-MIMO ANC system consists of one reference signal, four loudspeakers and six microphones. The results from a field test are presented in the paper and the results are commented.
This paper treats the practical aspects of the prediction, implementation and verification of an ... more This paper treats the practical aspects of the prediction, implementation and verification of an active noise control system. The system was implemented in a mock-up of a Saab 340 propeller aircraft. A search algorithm, based on simulated annealing using the metropolis sampler was used to determine the positions for the control sources and sensors. The sound field was generated by a specially designed noise simulation system, using 12 individually controlled loudspeakers and a DSP--based signal generator. A version of the individually normalized complex lms algorithm was implemented for the control of the sound field. The prediction and verification of the active control system, was made in 20 evaluation positions, distributed at ear level above the seats. This is the second paper in a series of two, concerning the preparation, selection and verification of an active noise control system. Part I contains a theoretical treatment with some general guidelines for the implementation. Paper II is focused on the practical aspects of the implementation and verification.
This article’s pivotal theme is: “How to compose a site-specific sound-art installation for a com... more This article’s pivotal theme is: “How to compose a site-specific sound-art installation for a commercial space in order to improve conditions, while taking perceptual, social, aesthetical, temporal and spatial criteria into account” The interdisciplinary, art-based research approach is derived from the concept of acousmatics, i.e. the process of apprehending any sound, the source of which is invisible. Acousmatic perception concerns the everyday identification process; when lacking visual contact with the sound source, we automatically seek references, such as social (what produces the sound and what is my relation to it?), aesthetical, spatial and temporal (e.g. orientation and demarcation). The acousmatic concept identifies phenomena based on individually, culturally and spatially conditioned experiences. Today, a shopping culture dominates urban space. Indoor malls expose us to all types of acousmatically perceived sounds: jingles, signals, music and muzak from public loudspeakers, mobile devices, etc. In this respect, one could claim that the soundscape of the shopping culture embodies an acousmatic environment. In 2009, the research and sound-art group Urban Sound Institute (USIT) created a permanent sound installation in a shopping mall (Gallerian) located in downtown Stockholm. This installation serves as a case study for the present paper. The artistic assignment involved the creation of a meeting place without material devices as well as the enhancement of the overall atmosphere. The research objective was to elucidate different qualities of the sound installation in regard to the acousmatics of the shopping mall, promoting discussions on the articulation of sound-space configurations in relation to time and site-specific context, issues on musical-architectural qualities as well as objective, subjective and inter-subjective interrelationships between the experience of the sound-art installation and the experience of the shopping mall soundscape. Other applied, interrelated concepts are metabolic environment and masking- and cutting effects.
Sound and other spaces is a book about urban sound environments, sound art, acoustic space, and s... more Sound and other spaces is a book about urban sound environments, sound art, acoustic space, and spatial aspects of sound. The texts in this book comprise personal reflections on sound quality and sound awareness, sound design and audio editing, technical solutions for artistic problems, and how sound can be composed and used in architectural design and city planning. In texts and images the authors present a number of projects performed within the artistic and interdisciplinary research group Urban Sound Institute (USIT). We hope that readers will find this book handy and easy to use and that it will serve as a bridge between specialists and an interested general public.
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