| 1. |
- Bard, Delphine, et al.
(författare)
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About phase optimization in multitone excitations
- 2008
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Ingår i: Audio Engineering Society - 125th Audio Engineering Society Convention 2008. - 9781605607122 ; 2, s. 858-861
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Konferensbidrag (refereegranskat)abstract
- Multitone signals are often used as excitation for the characterization of audio systems. The frequency spectrum of the response consists of harmonics of the frequencies contained in the excitation and intermodulation products. Beside the choice of frequencies, in order to avoid frequency overlapping, there is also the need to choose adequate magnitudes and phases for the different components that constitute the multitone signal. In this study, we will investigate how the choice of the phases will impact the properties of the multitone signal, but also how it will affect the performances of a compensation method based on Volterra kernels and using multitone signals as an excitation.
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| 2. |
- Bard, Delphine
(författare)
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Horn loudspeakers nonlinearity comparison and linearization using volterra series
- 2008
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Ingår i: Audio Engineering Society - 124th Audio Engineering Society Convention 2008. - 9781605602950 ; 1, s. 57-66
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Konferensbidrag (refereegranskat)abstract
- The characterization of a weakly nonlinear electroacoustic device with usual methods of measurement (THD, intermodulation) does not illustrate the nonlinearities themselves, but only some of their effects. Device linearization can be achieved by applying the inverse nonlinearity upstream of the device, under the condition that the nonlinearity law is known in detail. This paper presents nonlinearities behavior comparison of horn loudspeakers of different frequency ranges using an experimental method of weak nonlinearity characterization and compensation, based on a representation of the nonlinearity by Volterra series using multitone excitations.
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| 3. |
- Bard, Delphine, et al.
(författare)
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Human footsteps induced floor vibration.
- 2008
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Ingår i: The Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 123:5, s. 3356-3356
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Tidskriftsartikel (refereegranskat)abstract
- The generation of the impact sound by the act of the human walk involves two factors, the characters of the footfall and the shape of the induced floor deflection. The footfall noise is created by the impact excitation and the characters of the footfall depend on the foot-ware: the heels and the frequencies of the footfall. The shape of the floor deflection depends rather on the geometrical walking pattern and the construction of the floor structure. In this investigation, the vibration patter of the light-weight construction floor is created by the same walking object, a male with common height. The excitation from the person to the floor in the FE simulations is a function of the length of the foot and the weight of the walking object. The geometrical time history is of the foot step allows it to have different directions in the room. Since the excitation is assumed to be deterministic, differences between the excitation frequencies are estimated from the video records. The goal of this investigation is to determine the difference of the floor structure deflections between two different walking paths: one is perpendicular to the bearing beams and the other is the diagonal path.
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| 4. |
- Bard, Delphine
(författare)
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Investigation of wooden floor junction in terms of sound wave propagation
- 2009
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Ingår i: 16th International Congress on Sound and Vibration 2009, ICSV 2009. - 9781615677368 ; 3, s. 1306-1311
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Konferensbidrag (refereegranskat)abstract
- In modern building construction, where light weight structures are preferred for cost reasons, the sound transmission is often a problem to be considered carefully, hence the many studies addressing this issue. Various modal methods are frequently used to investigate the vibration pattern of light weight building structures in the low frequency range. The experimental determination of time average transmission and reflection coefficient has been developed for a wooden floor. In this investigation the wave approach is combined with the continuity equation. By doing so, both the flexural wave propagation and the in-plane wave motion can be taken into account. The mismatch impedance is also an important factor, since there is a change of material at the junction, and is therefore included in this study. The scattering matrix formulation is used to separate the transmitted wave and the reflected wave as the structural wave propagates towards a junction, but also to calculate the corresponding transmission and reflection coefficients. One type of junction has been studied with the help of accelerometer matrices: the T junction of a floor structure, together with its reinforcement beams. The experimental results are presented and commented.
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| 5. |
- Bard, Delphine, et al.
(författare)
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Measurements of vibration in wooden floor induced by walking
- 2009. - PART 3
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Ingår i: 8th European Conference on Noise Control 2009, EURONOISE 2009. - 9781615676804 ; 31
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Konferensbidrag (refereegranskat)abstract
- Timber floors receive a lot of attention nowadays because of their advantages, such as cost effectiveness, recyclability. On the other hand, more and more complains arise again this type of structures, related to the propagation of low frequency vibrations induced by human activities. Most problems are caused by human walking, more exactly foot impacts, which generate a harmonic force whose frequency is close to the natural frequency of the floor. The present investigation is focused on measurements and subjective tests; those were performed on an experimental wooden floor. The floor structure dimensions are 4.8 m by 2.4 m. The average spacing between the beams is 0.53 m and the height of the 6 supports is 4.5 cm. The subjective tests were performed according to Talja & Toratti's method. The measurements of accelerations induced by a walking person and the results from the subjective tests were then used to evaluate existing vibration criteria.
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| 6. |
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| 7. |
- Bard, Delphine, et al.
(författare)
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Newborn pain cry analysis based on pitch frequency tracking.
- 2008
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Ingår i: The Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 123:5
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the newborn pain cry analysis is to test the hypothesis that cry can be used as a tool to detect signs of nocioceptive pain. Previous studies applying signal processing techniques to analyze the sound of these cries have been done. The subject of this paper is to adapt and improve the original method with the help of new signal processing methods. The pitch frequency is extracted from the waveform of the recorded babies' cries using time domain methods. The fluctuations of this parameter are analyzed in terms of jitter. In particular, a sliding buffer approach is presented, as well as an improvement of the Average Mean Difference Function (AMDF). Comparison between original and news results has been done.
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| 8. |
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| 9. |
- Bard, Delphine, et al.
(författare)
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Structure borne sound investigation of a light weight floor with the help of Markov chain walking patterns
- 2009
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Ingår i: 16th International Congress on Sound and Vibration 2009, ICSV 2009. - 9781615677368 ; 5, s. 2982-2987
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Konferensbidrag (refereegranskat)abstract
- Each person has a very individual way of walking, though persons having the same sex and the same height, weight and age are likely to have similarities in the angle of the feet and the length of the stride. To simulate this, a number of Markov chains, that describe the stride, were created from experiments with 150 different males. The Markov chains were then used to create an artificial person for simulations, with a height of between 181-185 cm and a weight of 80 kg, which was to walk over the length of the floor. Each stride contained both heel and toe excitation defined based on the mean value of each concurrent stride. The floor in the simulation, created with the help of FEM, is a lightweight floor built out of wooden beams and particle board on top. This system was chosen due to its low weight per square meter compared to the weight of the walking person which therefore can be set in motion more easily. From the FEM simulation the velocity of all points of the floor was extracted. The velocity was then used to calculate the radiated sound pressure from the floor to different points on the floor below. The radiation from the different points of the floor will be presented graphically for 3 different measurement points.
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| 10. |
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